bioRxiv Subject Collection: Neuroscience's Journal

Polyserine peptides are toxic and exacerbate tau pathology in mice
Polyserine domains mediate the association of nuclear RNA binding proteins with cytoplasmic tau aggregates that occurs across tauopathy models and patient samples. In cell lines, polyserine peptides co-localize with and promote formation of tau aggregates suggesting the cytoplasmic mislocalization of polyserine-containing proteins might contribute to human disease. Moreover, polyserine can be produced by repeat associated non-AUG translation in CAG repeat expansion diseases. However, whether polyserine expressed in a mammalian brain is toxic and/or can exacerbate tau pathology is unknown. Here, we used AAV9-mediated delivery to express a 42-repeat polyserine protein in wild-type and tau transgenic mouse models. We observe that polyserine expression has toxic effects in wild-type animals indicated by reduced weight, behavioral abnormalities and a striking loss of Purkinje cells. Moreover, in the presence of a pathogenic variant of human tau, polyserine exacerbates disease markers such as phosphorylated and insoluble tau levels and the seeding capacity of brain extracts. These findings demonstrate that polyserine domains can promote tau-mediated pathology in a mouse model and are consistent with the hypothesis that cytoplasmic mislocalization of polyserine containing proteins might contribute to the progression of human tauopathies.

Microscopic deconstruction of cortical circuit stimulation by transcranial ultrasound
Transcranial Ultrasound Stimulation (TUS) can noninvasively and reversibly perturb neuronal activity, but the mechanisms by which ultrasound engages brain circuits to induce functional effects remain unclear. To elucidate these interactions, we applied TUS to the cortex of awake mice and concurrently monitored local neural activity at the acoustic focus with two-photon calcium imaging. We show that TUS evokes highly focal responses in three canonical neuronal populations, with cell-type-specific dose dependencies. Through independent parametric variations, we demonstrate that evoked responses collectively scale with the time-average intensity of the stimulus. Finally, using computational unmixing we propose a physiologically realistic cortical circuit model that predicts TUS-evoked responses as a result of both direct effects and local network interactions. Our results provide a first direct evidence of TUS's focal effects on cortical activity and shed light on the complex circuit mechanisms underlying these effects, paving the way for TUS's deployment in clinical settings.

Cannabinoids shift the basal ganglia miRNA m6A methylation profile towards an anti-inflammatory phenotype in SIV-infected Rhesus macaques
Epitranscriptomic modifications modulate diverse biological processes, such as regulation of gene expression, abundance, location and function. In particular, N6-methyladenosine (m6A) methylation has been shown to regulate various disease processes, including cancer and inflammation. While there is evidence that m6A modification is functionally relevant in neural development and differentiation, the role of m6A modification in HIV neuropathogenesis is unknown. Here, we identified direct m6A modifications in miRNAs from BG tissues of Rhesus Monkeys (RMs) that were either vehicle-treated uninfected (VEH), SIV-infected combination anti-retroviral therapy (cART) treated (VEH/SIV/cART), or THC:CBD treated VEH/SIV/cART (THC:CBD/SIV/cART) RMs. We detected m6A modifications across all BG tissues. SIV infection promoted an overall hypomethylated m6A profile. While the overall hypomethylated m6A profile was not significantly impacted by THC:CBD treatment, specific miRNAs, particularly those predicted to target proinflammatory genes showed markedly reduced m6A methylation levels compared to the VEH treated RMs. Additionally, we found that specific BG tissue miRNAs bearing m6A epi-transcriptomic marks were also transferred to BG-derived extracellular vesicles (EVs). Mechanistically, we identified the DRACH motif of the seed region of miR-194-5p to be significantly m6A hypomethylated, which was predicted to directly target STAT1, an important interferon-activated transcription factor known to drive neuroinflammation, in diseases ranging from Alzheimer to Parkinson and Huntington disease. Notably, THC:CBD treatments significantly reduced m6A methylation of 43 miRNA species directly involved in regulating CNS network genes, thus providing a possible mechanist explanation on the beneficial effects of THC:CBD treatments noted in several disease involving neuroinflammation. Our findings also underscore the need for investigating the qualitative, posttranscriptional modification changes in the RNA profiles along with the more traditional, qualitative alterations in pathological conditions or after various treatment regimens.

A striosomal accumbens pathway drives compulsive seeking behaviors through an aversive Esr1+ hypothalamic-habenula circuit.
The lateral hypothalamic area (LHA) integrates external stimuli with internal states to drive the choice between competing innate or value-driven motivated behaviors. Projections from the LHA to the lateral habenula (LHb) shape internal states, with excitatory estrogen receptor 1-expressing (Esr1+) LHA-LHb neurons driving aversive responses and sustained negative states. Here, we identify and functionally characterize a specific projection from the nucleus accumbens (ACB) that targets Esr1+ LHA-LHb neurons. Using cell-type-specific tracing of monosynaptic inputs, single-nucleus RNA sequencing, and neuroanatomical mapping, we demonstrate that the Esr1+ LHA-LHb pathway receives a major input from a striosomal Tac1+/Tshz1+/Oprm1+ ACB neuron subtype. Intersectional cell-type-specific and input-output defined optogenetic manipulation of this ACB-LHA-LHb pathway revealed its role in signaling aversion after repeated activation, with the negative behavioral state being dependent on recruitment of Esr1+ LHA-LHb neurons. Importantly, we found that activation of the D1+ ACB-LHA pathway drives reward-independent compulsive-like seeking behaviors, expressed as compulsive digging or poking behaviors. We found that these complex yet stereotyped behaviors compete with highly motivated states and can override the need for natural rewards or social stimuli. Our findings reveal a discrete striosomal Tac1+ ACB projection targeting the aversive Esr1+ LHA-LHb pathway as a key circuit that promotes compulsive seeking behaviors over goal-directed actions.

Mapping Synaptic Ensembles Through In Vitro Functional Cell Assemblies
In memory circuits, synaptic engrams consist of ensembles of strengthened synapses that form between engram neurons encoding distinct memory traces. As proposed in Hebb's seminal postulate, these potentiated synapses enable the functional cell assembly essential for neuronal wiring. While existing technologies can track potentiated synapses in behaving animals, understanding in vivo spatial-temporal organization of synaptic engrams remains challenging. We developed an in vitro hybrid system that integrates digital light processing with optogenetics and used optical stimulation to synchronize the firing patterns of two-neuron modules within a network, supporting Hebb's postulate experimentally. After illumination, we observe that synapses predominantly strengthen on dendrites between the two illuminated neurons, reflecting neuron responses to the wiring activity. This presents a robust conceptual foundation for our methodology. Our setup also allows direct target illumination and strengthening of synaptic ensembles, granting spatial-temporal control over the synaptic networks. Building on Hebb's theoretical framework, our system offers a solid experimental approach to test the core principles of synaptic engrams

Cerebral Small Vessel Disease genetic determinant TRIM47 controls brain homeostasis via the NRF2 antioxidant system
Cerebral small vessel disease (SVD) is a leading cause of strokes and a significant contributor to dementia, yet the precise mechanisms underlying its pathogenesis remain elusive. In a recent whole-exome association study involving population cohorts with SVD, we identified a variant on TRIM47 locus. The ubiquitin ligase TRIM47 is highly expressed in brain endothelial cells (ECs), suggesting its potential role in blood brain barrier (BBB) integrity. Here, we show that TRIM47 regulates brain ECs resilience and adaptive responses to oxidative stress by binding to KEAP1, stabilizing NRF2 protein levels and promoting NRF2 antioxidant signaling pathway. In vivo, Trim47-deficient mice exhibit downregulation of NRF2 target genes, BBB dysfunction, astrogliosis and cognitive impairments. Endothelial-specific deletion of Trim47 recapitulates this vascular dementia phenotype, emphasizing the critical role of endothelial TRIM47 in protecting brain function. Treatment with the NRF2 activator tert-butylhydroquinone normalized BBB integrity and cognitive function in Trim47-deficient mice, highlighting the role of TRIM47 in driving brain homeostasis through NRF2 pathway activation. This work indicates that the loss of the protective TRIM47/NRF2 axis may increase the susceptibility to developing human SVD and that targeting the TRIM47/NRF2 axis could offer novel therapeutic strategies for vascular dementia and related neurovascular diseases.

Distinct roles of SNR, speech Intelligibility, and attentional effort on neural speech tracking in noise
Robust neural encoding of speech in noise is influenced by several factors, including signal-to-noise ratio (SNR), speech intelligibility (SI), and attentional effort (AE). Yet, the interaction and distinct role of these factors remain unclear. In this study, fourteen native English speakers performed selective speech listening tasks at various SNR levels while EEG responses were recorded. Attentional performance was assessed using a repeated word detection task, and attentional effort was inferred from subjects' gaze velocity. Results indicate that both SNR and SI enhance neural tracking of target speech, with distinct effects influenced by the previously overlooked role of attentional effort. Specifically, at high levels of SI, increasing SNR leads to reduced attentional effort, which in turn decreases neural speech tracking. Our findings highlight the importance of differentiating the roles of SNR, SI, and AE in neural speech processing and advance our understanding of how noisy speech is processed in the auditory pathway.

Decoding the Unintelligible: Neural Speech Tracking in Low Signal-to-Noise Ratios
Understanding speech in noisy environments is challenging for both human listeners and technology, with significant implications for hearing aid design and communication systems. Auditory attention decoding (AAD) aims to decode the attended talker from neural signals to enhance their speech and improve intelligibility. However, whether this decoding remains reliable when speech intelligibility is severely degraded in real-world listening conditions remains unclear. In this study, we investigated selective neural tracking of the attended speaker under adverse listening conditions. Using EEG recordings in a multi-talker speech perception task with varying SNR, participants' speech perception was assessed through a repeated-word detection task, while neural responses were analyzed to decode the attended talker. Despite substantial degradation in intelligibility, we found that neural tracking of attended speech persists, suggesting that the brain retains sufficient information for decoding. These findings demonstrate that even in highly challenging conditions, AAD remains feasible, offering a potential avenue for enhancing speech intelligibility in brain-informed audio technologies, such as hearing aids, that leverage AAD to improve speech perception in real-world noisy environments.

DeepFocus: A Transnasal Approach for Optimized Deep Brain Stimulation of Reward Circuit Nodes
Objective: Transcranial electrical stimulation (TES) is an effective technique to modulate brain activity and treat diseases. However, TES is primarily used to stimulate superficial brain regions and is unable to reach deeper targets. The spread of injected currents in the head is affected by volume conduction and the additional spreading of currents as they move through head layers with different conductivities, as is discussed in [1]. In this paper, we introduce DeepFocus, a technique aimed at stimulating deep brain structures in the brain's "reward circuit" (e.g. the orbitofrontal cortex, Brodmann area 25, amygdala, etc.). Approach: To accomplish this, DeepFocus utilizes transnasal electrode placement (under the cribriform plate and within the sphenoid sinus) in addition to electrodes placed on the scalp, and optimizes current injection patterns across these electrodes. To quantify the benefit of DeepFocus, we develop the DeepROAST simulation and optimization platform. DeepROAST simulates the effect of complex skull-base bones' geometries on the electric fields generated by DeepFocus configurations using realistic head models. It also uses optimization methods to search for focal and efficient current injection patterns, which we use in our simulation and cadaver studies. Main Results. In simulations, optimized DeepFocus patterns created larger and more focal fields in several regions of interest than scalp-only electrodes. In cadaver studies, DeepFocus patterns created large fields at the medial orbitofrontal cortex (OFC) with magnitudes comparable to stimulation studies, and, in conjunction with established cortical stimulation thresholds, suggest that the field intensity is sufficient to create neural response, e.g. at the OFC. Significance. This minimally invasive stimulation technique can enable more efficient and less risky targeting of deep brain structures to treat multiple neural conditions.

Ethanol drinking sex-dependently alters cortical IL-1β synaptic signaling and cognitive behavior in mice
Individuals with alcohol use disorder (AUD) struggle with inhibitory control, decision making, and emotional processing. These cognitive symptoms reduce treatment adherence, worsen clinical outcomes, and promote relapse. Neuroimmune activation is a key factor in the pathophysiology of AUD, and targeting this modulatory system is less likely to produce unwanted side effects compared to directly targeting neurotransmitter dysfunction. Notably, the cytokine interleukin-1{beta} (IL-1{beta}) has been broadly associated with the cognitive symptoms of AUD, though the underlying mechanisms are not well understood. Here we investigated how chronic intermittent 24-hour access two bottle choice ethanol drinking affects medial prefrontal cortex (mPFC)-related cognitive function and IL-1 synaptic signaling in male and female C57BL/6J mice. In both sexes, ethanol drinking decreased reference memory and increased mPFC IL-1 receptor 1 (IL-1R1) mRNA levels. In neurons, IL-1{beta} can activate either pro-inflammatory or neuroprotective intracellular pathways depending on the isoform of the accessory protein (IL-1RAcP) recruited to the IL-1R1 complex. Moreover, ethanol drinking sex-dependently shifted mPFC IL-1RAcP isoform gene expression and IL-1{beta} regulation of mPFC GABA synapses, both of which may contribute to female mPFC resiliency and male mPFC susceptibility. This type of signaling bias has become a recent focus of rational drug development. Therefore, in addition to increasing our understanding of how IL-1{beta} sex-dependently contributes to mPFC dysfunction in AUD, our current findings also support the development of a new class of pharmacotherapeutics based on biased IL-1 signaling.

A novel epigenetic clock for rhesus macaques unveils an association between early life adversity and epigenetic age acceleration
Because DNA methylation changes reliably with age, machine learning models called epigenetic clocks can estimate an individuals age based on their DNA methylation profile. This epigenetic measure of age can deviate from ones true age, and the difference between the epigenetic age and true age, known as epigenetic age acceleration (EAA), has been found to directly correlate with morbidity and mortality in adults. Emerging evidence suggests that EAA is also associated with aberrant health outcomes in children, making epigenetic clocks useful tools for studying aging and development. We developed two highly accurate epigenetic clocks for the rhesus macaque, utilizing 1,008 blood samples from 690 macaques between 2 days and 23.4 years of age with diverse genetic backgrounds and exposure to environmental conditions. The first clock, which is trained on all samples, achieves a Pearson correlation between true age and predicted age of 0.983 and median absolute error of 0.210 years. To study phenotypes during development, the second clock is optimized for macaques younger than 6 years and achieves a Pearson correlation of 0.974 and a median absolute error of 0.148 years. Using the latter clock, we investigated whether epigenetic aging is affected by early life adversity in the form of infant maltreatment. Our data suggests that maltreatment and increased hair cortisol levels are associated with epigenetic age acceleration right after the period of maltreatment.

Ramping dissociates motor and cognitive sequences in the parietal and prefrontal cortices
Humans complete different types of sequences as a part of everyday life. These sequences can be divided into two important categories: those that are abstract, in which the steps unfold according to a rule at super-second to minute time scale, and those that are motor, defined solely by individual movements and their order which unfold at the sub-second to second timescale. For example, the sequence of making spaghetti consists of abstract tasks (preparing the sauce and cooking the noodles) and nested motor actions (stir pasta water). Previous work shows neural activity increases (ramps) in the rostrolateral prefrontal (RLPFC) during abstract sequence execution (Desrochers et al., 2015, 2019). During motor sequence production, activity occurs in regions of the prefrontal cortex (Yewbrey et al., 2023). However, it remains unknown if ramping is a signature of motor sequence production as well or solely an attribute of abstract sequence monitoring and execution. We tested the hypothesis that significant ramping activity occurs during motor sequence production in the RLPFC. Contrary to our hypothesis, we did not observe significant ramping activity in the RLPFC during motor sequence production, but we found significant activity in bilateral inferior parietal cortex, in regions distinct from those observed during an abstract sequence task. Our results suggest different prefrontal-parietal mechanisms may underlie abstract vs. motor sequence execution.

hMT+ Activity Predicts the Effect Of Spatial Attention On Surround Suppression
Surround suppression refers to the decrease in behavioral sensitivity and neural response to a central stimulus due to the presence of surrounding stimuli. Several aspects of surround suppression in human motion perception have been studied in detail, including its atypicality in some clinical populations. However, how the extent of spatial attention affects the strength of surround suppression has not been systematically studied before. To address this question, we presented human participants with 'center' and 'surround' drifting gratings and sought to find whether attending only to the center ('narrow attention') versus both to the center and surround ('wide attention') modulates the suppression strength in motion processing. Using psychophysics and functional magnetic resonance imaging (fMRI), we measured motion direction discrimination thresholds and cortical activity in the primary visual cortex (V1) and middle temporal complex (hMT+). We found increased perceptual thresholds and, thus, stronger surround suppression under the wide attention condition. We also found that the pattern of hMT+ activity was consistent with the behavioral results. Furthermore, a mathematical model that combines spatial attention and divisive normalization was able to explain the pattern in the behavioral and fMRI results. These findings provide a deeper understanding of how attention affects center-surround interactions and suggest possible neural mechanisms with relevance to both basic and clinical vision science.

Contribution of rat insular cortex to stimulus-guided action
Anticipating rewards is fundamental for decision-making. Animals often use cues to assess reward availability and to make predictions about future outcomes. The gustatory region of the insular cortex (IC), the so-called gustatory cortex, has a well-established role in the representation of predictive cues, such that IC neurons encode both a general form of outcome expectation as well as anticipatory outcome-specific knowledge. Here, we used Pavlovian-instrumental transfer (PIT) in male rats to assess if the IC is also required for predictive cues to exert both a general and specific influence over instrumental actions. Chemogenetic inhibition of IC abolished the ability of a reward-predictive stimulus to energize instrumental responding for reward. This deficit in general transfer was evident whether the same or different outcomes were used in the Pavlovian and instrumental conditioning phases. We observed a similar deficit in specific PIT, such that rats with IC inhibition failed to use a reward-predictive stimulus to guide choice toward actions that deliver the same food reward. Finally, we show that rats with IC inhibition also fail to show outcome-selective reinstatement. Together, these data suggest a crucial role for IC in the representation of appetitive outcomes, and particularly in using this representation to guide instrumental action.

The representation of stimulus features during stable fixation and active vision
Predictive updating of object spatial coordinates from retinotopic pre-saccadic to post-saccadic positions contributes to stable visual perception. However, whether object features are predictively represented at the remapped location remains contested. Many previous studies showing evidence of feature remapping neglect the spatially invariant representation of features in the visual system. For example, feature-based attention boosts attended features across the entire visual field, potentially contributing to the maintenance of stimulus features across saccades. We set out to characterise the spatiotemporal dynamics of feature processing during stable fixation and active vision. To do so, we applied multivariate decoding methods to electroencephalography (EEG) data collected while participants viewed brief visual stimuli. Stimuli appeared at different locations across the visual field at either high or low spatial frequency (SF). During fixation, classifiers were trained to decode SF presented at one parafoveal location and cross-tested on SF from either the same, adjacent or more peripheral locations. When training and testing on the same location, SF was classified shortly after stimulus onset (~80 ms). Decoding of SF at locations farther from the trained location emerged later (~150-300 ms), with decoding latency modulated by eccentricity. This analysis provides a detailed time course for the spread of feature information across the visual field. Next, we investigated how active vision impacts the emergence of SF information. In the presence of a saccade, the decoding time of peripheral SF at parafoveal locations was accelerated, indicating predictive anticipation of SF due to the saccade. Crucially however, this predictive effect was not limited to the specific remapped location. Rather, peripheral SF was correctly classified, at an accelerated time course, at all parafoveal positions. This indicates a spatially coarse remapping of stimulus features during active vision, likely enabling a smooth transition on saccade landing.

Changes in cortical grasp-related activity before and after object contact
Grasping, a seemingly simple manual behavior, requires the coordinated control of dozens of joints, guided by sensory signals from muscles, tendons, and skin. As the motor cortex controls finger movement and exerted forces, the somatosensory cortex must process the barrage of proprioceptive and tactile signals that convey details about the object's shape, its local features (e.g., edges and curvature), and forces applied to it. In the present study, we aimed to understand the transformation in these sensorimotor signals at the time of contact with an object. We analyzed object-specific signals in the primary motor cortex (M1) and Brodmann's areas 3a, 1, and 2 of the somatosensory cortex of macaque monkeys. We found object information distributed throughout sensorimotor cortex, some of which was independent of contact, while most was dramatically altered by it. While all areas conveyed object information after contact, those carrying postural representations (M1, area 3a) were also informative before contact, during the hand pre-shaping epoch. Although their mappings retained some similarity between epochs, decoders built on the pre-contact epoch did not perform well on the post-contact epoch, suggesting intermixing between postural and force-related signals. After contact, individual neurons in M1 retained some information about the object, but the populational encoding of object identity weakened, reflecting perhaps, the delegation of control to subcortical structures. Unexpectedly, although it was active, area 2 was uninformative about the object before contact, despite its proprioceptive inputs. However, after contact, area 2 emerged as the most informative region of any epoch, likely reflecting its convergent proprioceptive and cutaneous input, and supporting its proposed role in haptic object perception. These results underscore the diverse activity within the sensorimotor cortex during grasping, highlighting the intricate neural processes involved in this fundamental behavior.

Lipidomic Profiling Reveals Shared and Distinct Pathological Signatures in Sporadic Parkinson's Disease and GBA Mutation Carriers: Implications for Disease Mechanisms
Parkinson's Disease (PD) is a neurodegenerative disorder characterised by the deposition of protein inclusions, called Lewy Bodies (LBs), in neurons. LBs are heterogeneous structures whose main constituent is the protein alpha-synuclein (alpha S) and that are also composed of lipid molecules. Disruptions in the levels of specific lipids, including sphingolipids, fatty acids, and cholesterol, have been associated with PD, suggesting a role of lipids in the emergence and spreading of S and PD pathology. Using a combination of shotgun lipidomics and biochemical analyses of PD amygdala homogenates, we have shown that long sporadic disease duration and GBA risk mutation are associated with a decrease in the protein and activity levels of glucocerebrosidase (GCase) activity and in cardiolipin levels and an increase in those of pathological alpha S, cholesterol, diacylglycerides, sphingolipids and specific glycerophospholipids (GPL). Long sporadic PD and GBA risk mutations also led to a shift from long unsaturated to short saturated GPL and from short to long sphingomyelin and ceramide. Moreover, the levels of lipid classes and species affected by long sPD and GBA risk mutations were found to correlate negatively with GCase activity and positively with pathological alpha S levels. We found that GBA mutation with mild phenotype affects lipid levels in the same direction as GBA risk mutation and long sPD but to a lesser extent and that GBA mutation carriers with severe phenotype led to changes in the opposite direction for the same lipids. Finally, the lipid analyses of LB- and small aggregates enriched fractions show that long sPD and GBA risk mutations led to the same changes in the levels and species distribution of GPL and SL than in homogenates but to a lesser extent. Together, these results suggest the need for patient stratification in clinical trials of therapeutic interventions in PD-GBA and that successful therapeutics against PD-GBA should be considered for sporadic PD.

The Growing Little Brain: Cerebellar Functional Development from Cradle to School
Despite the cerebellum's crucial role in brain functions, its early development, particularly in relation to the cerebrum, remains poorly understood. Here, we examine cerebellocortical connectivity using over 1,000 high-quality resting-state functional MRI scans of children from birth to 60 months. By mapping cerebellar topography with fine temporal detail for the first time, we show the hierarchical and contralateral organization of cerebellocortical connectivity from birth. We observe dynamic shifts in cerebellar network gradients, which become more focal with age while maintaining stable anchor points similar to adults, highlighting the cerebellum's evolving yet stable role in functional integration during early development. Our findings provide the first evidence of cerebellar connections to higher-order networks at birth, which generally strengthen with age, emphasizing the cerebellum's early role in cognitive processing beyond sensory and motor functions. Our study provides insights into early cerebellocortical interactions, reveals functional asymmetry and sexual dimorphism in cerebellar development, and lays the groundwork for future research on cerebellum-related disorders in children.

Food intake enhances hippocampal sharp wave-ripples
Effective regulation of energy metabolism is critical for survival. Metabolic control involves various nuclei within the hypothalamus, which receive information about the energy state of the body and coordinate appropriate responses to maintain homeostasis, such as thermogenesis, pancreatic insulin secretion, and food-seeking behaviors. It has recently been found that the hippocampus, a brain region traditionally associated with memory and spatial navigation, is also involved in metabolic regulation. Specifically, hippocampal sharp wave ripples (SWRs), which are high-frequency neural oscillations supporting memory consolidation and foraging decisions, have been shown to influence peripheral glucose metabolism. However, whether SWRs are enhanced by recent feeding, when the need for glucose metabolism increases, and if so, whether feeding-dependent modulation of SWRs is communicated to other brain regions involved in metabolic regulation, remains unknown. To address these gaps, we recorded SWRs from the dorsal CA1 region of the hippocampus of mice during sleep sessions before and after consumption of meals of varying caloric values. We found that SWRs occurring during sleep are significantly enhanced following food intake, with the magnitude of enhancement being dependent on the caloric content of the meal. This pattern occurred under both food-deprived and ad libitum feeding conditions. Moreover, we demonstrate that neuronal populations in the lateral hypothalamus, which regulates food intake, exhibit robust SWR-triggered increase in activity. These findings identify the satiety state as a factor modulating SWRs and suggest that hippocampal-lateral hypothalamic communication is a potential mechanism by which SWRs could modulate peripheral metabolism and food intake.

Gasdermin D is activated but does not drive neurodegeneration in SOD1G93A model of ALS: Implications for targeting pyroptosis
Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron loss, microgliosis, and neuroinflammation. While pyroptosis, an inflammatory form of programmed cell death, has been implicated in ALS, the specific role of Gasdermin D (GSDMD) - the primary executioner of pyroptosis - remains unexplored. In this study, we examined the function of GSDMD in the well-established SOD1G93A mouse model of ALS. Our results showed robust GSDMD activation in the spinal cords of SOD1G93A animals across two strain backgrounds, with elevated expression in Iba1+ microglia. To explore its role in disease progression, we bred B6.SOD1G93A mice onto a GSDMD-deficient background. In comparing SOD1G93A; Gsdmd+/+ and SOD1G93A; Gsdmd-/- mice, we found that Gsdmd loss did not affect disease onset, weight loss, or grip strength decline in either male or female animals. Notably, GSDMD deficiency resulted in a modest but statistically significant increase in mortality in SOD1G93A mice. Moreover, GSDMD absence had minimal impact on astrogliosis, microgliosis and motor neuron loss. These findings show that while GSDMD is activated in the ALS mouse model, its loss does not mitigate key ALS behavioral phenotypes, gliosis or motor neuron loss. This study provides insights into the potential therapeutic relevance of targeting pyroptosis and inflammatory pathways in ALS.

Snapshot of 5-HT2A receptor activation in the mouse brain via IP1 detection
The distinct subjective effects that define psychedelics such as LSD, psilocybin or DOI as drug class are causally linked to activation of the serotonin 2A receptor (5-HT2AR). However, some aspects of 5-HT2AR pharmacology remain elusive, such as what molecular drivers differentiate psychedelic from non-psychedelic 5-HT2AR agonists. We developed an ex vivo platform to obtain snapshots of drug-mediated 5-HT2AR engagement of the canonical Gq/11 pathway in native tissue. This non-radioactive methodology captures the pharmacokinetic and pharmacodynamic events leading up to changes in inositol monophosphate (IP1) in the mouse brain. The specificity of this method was assessed by comparing IP1 levels in homogenates from the frontal cortex in DOI-treated wild-type and 5-HT2AR-KO animals compared to other brain regions, namely striatum and cerebellum. Furthermore, we encountered that head-twitch response (HTR) counts and IP1 in the frontal cortex were correlated. We observed that IP1 levels in frontal cortex homogenates from mice treated with LSD and lisuride vary in magnitude, consistent with LSD's 5-HT2AR agonism and psychedelic nature, and lisuride's lack thereof. MDMA evoked an increase of IP1 signal in the frontal cortex that were not matched by the serotonin precursor 5-HTP or the serotonin reuptake inhibitor fluoxetine. We attribute differences in the readout primarily to the indirect stimulation of 5-HT2AR by MDMA via serotonin release from its presynaptic terminals. This methodology enables capturing a snapshot of IP1 turnover in the mouse brain that can provide mechanistic insights in the study of psychedelics and other serotonergic agents pharmacodynamics.

Light modulates glucose and lipid homeostasis via the sympathetic nervous system
Light is an important environmental factor for vision, and for diverse physiological and psychological functions. Light can also modulate glucose metabolism. Here, we show that in mice, light is critical for glucose and lipid homeostasis by regulating the sympathetic nervous system, independent of circadian disruption. Light deprivation from birth elicits insulin hypersecretion, glucagon hyposecretion, lower gluconeogenesis, and reduced lipolysis by 6-8 weeks, in male, but not, female mice. These metabolic defects are consistent with blunted sympathetic activity, and indeed, sympathetic responses to a cold stimulus are significantly attenuated in dark-reared mice. Further, long-term dark rearing leads to body weight gain, insulin resistance, and glucose intolerance. Notably, metabolic dysfunction can be partially alleviated by 5 weeks exposure to a regular light-dark cycle. These studies provide insight into circadian-independent mechanisms by which light directly influences whole-body physiology and inform new approaches for understanding metabolic disorders linked to aberrant environmental light conditions.

Brain Pretargeted PET - New Horizons to Image CNS Targets with Monoclonal Antibodies
Antibodies are excellent targeting vector for molecular imaging. Slow pharmacokinetics and low blood-brain barrier penetration hinder their widespread application for molecular imaging within CNS. Improved brain uptake can be achieved via transferrin-mediated transcytosis. Pretargeted imaging can increase imaging contrast and reduce radiation exposure to the patient. Here, we report for the first time that pretargeted imaging of CNS targets using intravenously administered target vectors is feasible. Specific binding to A{beta}-bound antibody was achieved. We believe that this proof-of-concept study will facilitate molecular imaging of currently undruggable targets with antibodies where small molecule PET tracer discovery has been challenging.

Fluorescence lifetime-based FRET biosensors for monitoring N-terminal domain interactions of TDP-43 in living cells: A novel resource for ALS and FTD drug discovery
TAR DNA-binding protein 43 (TDP-43) pathological aggregates are widely implicated in Alzheimer's disease, frontotemporal dementia and amyotrophic lateral sclerosis. While therapeutic platforms targeting TDP-43 have predominantly targeted its aggregation, recent findings suggest that loss of functional TDP-43 dimers and multimers - essential for RNA processing - occur upstream of aggregation and is driven through disruption of N-terminal domain (NTD) interactions. Here, we demonstrate that these interactions are targetable via cellular fluorescence lifetime-based FRET biosensors which we used to screen the FDA-approved Selleck library. Our NTD-specific hit ketoconazole rescues sorbitol-induced TDP-43 mislocalization and aggregation, and ameliorates TDP-43 induced downregulation of SREBP2, a TDP-43 mRNA binding target with known implication in ALS. In addition, ketoconazole improves neurite outgrowth in a TDP-43 overexpressing neuron model and motor dysfunction in TDP-43 overexpressing C. elegans. Taken together, our platform represents a novel approach for targeting NTD-dependent TDP-43 interactions, and the identification of ketoconazole validates an exciting translational premise for TDP-43 drug discovery.

Structured stabilization in recurrent neural circuits through inhibitory synaptic plasticity
Inhibitory interneurons play a dual role in recurrently connected biological circuits: they regulate global neural activity to prevent runaway excitation, and contribute to complex neural computations. While the first role can be achieved through unstructured connections tuned for homeostatic rate stabilization, computational tasks often require structured excitatory-inhibitory (E/I) connectivity. Here, we consider a broad class of pairwise inhibitory spike-timing dependent plasticity (iSTDP) rules, demonstrating how inhibitory synapses can self-organize to both stabilize excitation and generate functionally relevant connectivity structures -- a process we call "structured stabilization". We show that in both E/I circuit motifs and large spiking recurrent neural networks the choice of iSTDP rule can lead to either mutually connected E/I pairs, or to lateral inhibition, where an inhibitory neuron connects to an excitatory neuron that does not directly connect back to it. In a one-dimensional ring network, if two inhibitory populations follow these distinct forms of iSTDP, the effective connectivity within the excitatory population self-organizes into a Mexican-hat-like profile with excitatory influence in the center and inhibitory influence away from the center. This leads to emergent dynamical properties such as surround suppression and modular spontaneous activity. Our theoretical work introduces a family of rules that retains the broad applicability and simplicity of spike-timing-based plasticity, while promoting structured, self-organized stabilization. These findings highlight the rich interplay between iSTDP rules, circuit structure, and neuronal dynamics, offering a framework for understanding how inhibitory plasticity shapes network function.

Balance performance in aged mice is dependent on unipolar brush cells
The vestibular processing regions of the cerebellum integrate vestibular information with other sensory modalities and motor signals to regulate balance, gaze stability, and spatial orientation. A class of excitatory glutamatergic interneurons known as unipolar brush cells (UBCs) are highly concentrated within the granule cell layer of these regions. UBCs receive vestibular signals directly from primary vestibular afferents and indirectly from mossy fibers. Each UBC excites numerous granule cells and could contribute to computations necessary for balance-related motor function. Prior research has implicated UBCs in motor function, but their influence on balance performance remains unclear, especially in aged mice that have age-related impairment. Here we tested whether UBCs contribute to motor coordination and balance by disrupting their activity with chemogenetics in aged and young mice. Age-related balance deficits were apparent in mice > 6 months old. Disrupting the activity of a subpopulation of UBCs caused aged mice to fall off a balance beam more frequently and altered swimming behaviors that are sensitive to vestibular dysfunction. These effects were not seen in young (7-week-old) mice. Thus, disrupting the activity of UBCs impairs mice with age-related balance issues and suggest that UBCs are essential for balance and vestibular function in aged mice.

Activation of Group II Metabotropic Glutamate Receptors in the Basolateral Amygdala Inhibits Reward Seeking Triggered by Discriminative Stimuli
Reward-associated cues are essential in guiding reward-seeking behaviours. These cues include conditioned stimuli (CSs) which occur following seeking actions and indicate reward delivery, and discriminative stimuli (DSs) which occur response-independently and signal reward availability. Metabotropic group II glutamate (mGlu2/3) receptors in the basolateral amygdala (BLA) modulate CS-guided reward seeking; however, their role in DS effects is unknown. We first developed a procedure to assess DS and CS effects on reward seeking in the same subjects within the same test session. Female and male rats first self-administered sucrose during sessions where discriminative stimuli signaled periods of sucrose availability (DS+) and unavailability (DS-). During DS+ presentations, active lever presses produced sucrose paired with a CS+. During DS- presentations, active lever presses produced a CS- and no sucrose. Across 14 sessions, rats learned to load up on sucrose during DS+ presentation and inhibit responding during DS- presentation. We then compared the effects of intra-BLA microinfusions of the mGlu2/3 receptor agonist LY379268 on cue-evoked sucrose seeking during an extinction test (no sucrose) where the DSs and CSs were presented response-independently. Before test, rats received intra-BLA microinjections of artificial cerebrospinal fluid (aCSF) or LY379268. Under aCSF, only the DS+ and DS+CS+ combined triggered increases in reward-seeking behaviour. The CS+ alone was ineffective. Intra-BLA LY379268 reduced sucrose seeking triggered by the DS+ and DS+CS+ combination. Thus, using a new procedure to test reward seeking induced by DSs and CSs, we show that BLA mGlu2/3 receptor activity mediates the conditioned incentive motivational effects of reward predictive DSs.

Persistent Na+ current couples seizure with Spreading depolarization in Scn8a gain-of-function mice
Spreading depolarization (SD) is a slowly propagating wave of massive cellular depolarization that transiently impairs the function of affected brain regions. While SD typically arises as an isolated hemispheric event, we previously reported that reducing M-type potassium current (IKM) by ablation of Kcnq2 in forebrain excitatory neurons results in tightly coupled spontaneous bilateral seizure-SD complexes in the awake mouse cortex. Here we find that enhanced persistent Na+ current due to gain-of-function (GOF) mutations in Scn8a (N1768D/+, hereafter D/+) produces a similar compound cortical excitability phenotype. Chronic DC-band EEG recording detected spontaneous bilateral seizure-SD complexes accompanied by seizures with a profound tonic component, which occurs predominantly during the light phase and were detected in the mutant mice across ages between P40-100. Laser speckle contrast imaging of cerebral blood flow dynamics resolved SD as bilateral wave of hypoperfusion and subsequent hour-lasting hypoperfusion in Scn8aD/+ cortex in awake head-restrained mice subjected to a subconvulsive PTZ. Subcortical recordings in freely moving mice revealed that approximately half of the spontaneous cortical seizure-SD complexes arose with concurrent SD-like depolarization in the thalamus and delayed depolarization in the striatum. In contrast, SD-like DC potential shifts were rarely detected in the hippocampus or upper pons. Consistent with the high spontaneous incidence in vivo, cortical slices from Scn8aD/+ mice showed a raised SD susceptibility, and pharmacological inhibition of persistent Na+ current (INaP), which is enhanced in Scn8aD/+ neurons, inhibited SD generation in cortical slices ex vivo, indicating that INaP contributes to SD susceptibility. Ex vivo Ca2+ imaging studies using acute brain slices expressing genetic Ca2+ sensor (Thy1-GCAMP6s) demonstrated that pharmacological activation of IKM suppressed Ca2+ spikes and SD, whereas IKM inhibitor drastically increased the frequency of Ca2+ spikes in the hippocampus of Scn8aD/+ mice, but not in WT, suggesting that IKM restrains the hyperexcitability resulting from Scn8a GOF mutation. Together, our study identifies a cortical SD phenotype in Scn8a GOF mice shared with the Kcnq2-cKO model of developmental epileptic encephalopathy and reveals that an imbalance of non-inactivating inward and outward membrane currents bidirectionally modulates spatiotemporal SD susceptibility.

Thrombolysis exacerbates cerebrovascular injury after ischemic stroke via a VEGF-B dependent effect on adipose lipolysis
Cerebrovascular injuries leading to edema and hemorrhage after ischemic stroke are common. The mechanisms underlying these events and how they are connected to known risk factors for poor outcome, like obesity and diabetes, is relatively unknown. Herein we demonstrate that increased adipose tissue lipolysis is a dominating risk factor for the development of a compromised cerebrovasculature in ischemic stroke. Reducing adipose lipolysis by VEGF-B antagonism improved vascular integrity by reducing ectopic cerebrovascular lipid deposition. Thrombolytic therapy in ischemic stroke using tissue plasminogen activator (tPA) leads to increased risk of hemorrhagic complications, substantially limiting the use of thrombolytic therapy. We provide evidence that thrombolysis with tPA promotes adipose tissue lipolysis, leading to a rise in plasma fatty acids and lipid accumulation in the ischemic cerebrovasculature after stroke. VEGF-B blockade improved the efficacy and safety of thrombolysis suggesting the potential use of anti-VEGF-B therapy to extend the therapeutic window for stroke management.

Rapid, interpretable, data-driven models of neural dynamics using Recurrent Mechanistic Models
Obtaining predictive models of a neural system is notoriously challenging. Detailed models suffer from excess model complexity and are difficult to fit efficiently. Simplified models must negotiate a tradeoff between tractability, predictive power and ease of interpretation. We present a new modelling paradigm for estimating predictive mechanistic-like models of neurons and small circuits that navigates these issues using methods from systems theory. The key insight is that membrane currents can be modelled using two scalable system components optimized for learning: linear state space models, and nonlinear artificial neural networks (ANNs). Combining these components, we construct two types of membrane currents: lumped currents, which are more flexible, and data-driven conductance-based currents, which are more interpretable. The resulting class of models --- which we call Recurrent Mechanistic Models (RMMs) --- can be trained in a matter of seconds to minutes on intracellular recordings during an electrophysiology experiment, representing a step change in performance over previous approaches. As a proof-of-principle, we use RMMs to learn the dynamics of two groups of neurons, and their synaptic connections, in the Stomatogastric Ganglion (STG), a well-known central pattern generator. We show that RMMs are efficiently trained using teacher forcing and multiple-shooting. Due to their reliability, efficiency and interpretability, RMMs enable qualitatively new kinds of experiments using predictive models in closed-loop neurophysiology experiments, and for online estimation of neural properties in living preparations.

Beyond the CTCT: Remote Structural Changes After VIM-MRgFUS in Essential Tremor
Introduction: Essential tremor (ET) is a progressive disorder characterized by altered network connectivity between the cerebellum, thalamus, and cortical regions. Magnetic Resonanceguided Focused Ultrasound (MRgFUS) of the ventral intermediate nucleus (VIM) is an effective, minimally invasive treatment for ET. Increasing clinical use in ET facilitates research on structural changes after thalamic lesions. Methods: Forty-six patients with medication-resistant ET underwent unilateral VIM-MRgFUS. Voxel-based morphometry was applied to investigate Gray Matter Volume (GMV) changes over a time span of 6 months in the whole brain and the thalamus in particular to investigate local and distant effects. Results: Clinically, contralateral tremor significantly decreased by 68 % at 6 months following MRgFUS. In addition to local changes in thalamic nuclei (VIM, ventral lateral posterior, centromedian thalamus and pulvinar), VBM revealed remote GMV decreases in the ipsilesional insula and the anterior cingulate cortex as well as the contralesional middle occipital gyrus. Increased GMV was found in both temporal gyri. There was no significant correlation between regional GMV declines and tremor improvement. However, temporal volume increases were associated with improved motor-related functional abilities and quality of life outcomes. Conclusion: Our findings implicate distributed structural changes following unilateral VIMMRgFUS. Structural losses could reflect Wallerian degeneration of VIM output neurons or plasticity due to decreased sensory input following tremor improvement.

Harmonization of Structural Brain Networks for Multi-site Studies
Research on structural networks often suffers from limited sample sizes and inherent selection biases in individual studies, which restrict their ability to address complex questions regarding human brain organization. Pooling data across studies is crucial for achieving a more comprehensive representation of the population and effectively managing individual heterogeneity; however, structural networks acquired from multiple sites are susceptible to significant site-related differences. This necessitates harmonization to mitigate biases and reveal true biological variability in multi-site analyses. Our work marks the first effort to develop and evaluate harmonization frameworks specifically for structural networks. We adapt several statistical approaches for harmonizing structural networks and provide a comprehensive evaluation to rigorously test their effectiveness. Our findings demonstrate that the adaptation of the Gamma Generalized Linear Model (gamma-GLM) outperforms other methods in modeling structural network data, effectively eliminating site-related effects in structural connectivity matrices and downstream graph-based analyses while preserving biological variability. Additionally, we highlight gamma-GLM's superiority in addressing confounding factors between site and age. Two practical applications further illustrate the utility of our harmonization framework in tackling common challenges in multi-site structural network studies. Specifically, harmonization using gamma-GLM enhances the transferability of brain age predictors to new datasets and facilitates data integration in patient studies, ultimately improving statistical power. Together, our work offers essential guidelines for harmonizing and integrating multi-site structural network studies, paving the way for more robust discoveries through collaborative research in the era of big data.

Characterizing dynamic functional connectivity in congenitally blind people using Hidden Markov Models
How does sensory experience influence the brain connectome? Early acquired blindness is known to trigger a large-scale alteration in brain connectivity. Previous studies have traditionally assessed stationary functional connectivity across all timepoints in scanning sessions. In this study we compared the dynamic nature of functional connectivity in sighted (50) and early/congenitally blind (33) individuals through the data-driven approach of Hidden Markov Models (HMM). Blind individuals showed increased fractional occupancy in two key brain states: one characterized by bilateral somatomotor activation and another by occipito-frontal activation, mainly in the left hemisphere. Conversely, sighted individuals more frequently occupied a state associated with Default Mode and Ventral Attentional networks. Network analysis revealed decreased connectivity in blind individuals within states frequently occupied by sighted individuals, particularly between visual and somatomotor regions. In contrast, states more often visited by blind individuals exhibited increased connectivity within the visual network, connecting multiple occipital regions with the temporal fusiform area, as well as between visual and prefrontal regions. These results suggest that the frequency of visiting specific brain states may contribute to the differences observed between blind and sighted individuals in stationary resting state functional connectivity. Together, these findings show the effectiveness of Hidden Markov Models in capturing the temporal dynamics of functional connectivity, revealing its variability over time. We found that early visual deprivation disrupts these dynamics, with blindness leading to prolonged activation of unimodal regions and increased connectivity within the visual network and between occipital and higher-order brain regions. Additionally, alterations in the chronnectome, defined as the functional connectome changing over time - specifically in the time spent visiting a state - may provide new insights into stationary functional connectivity patterns in blind individuals, establishing a foundation for understanding network connectivity dynamics following sensory deprivation.

Region-specific spreading depolarization drives aberrant post-ictal behavior
Confusion, aphasia, and unaware wandering are prominent post-ictal symptoms regularly observed in temporal lobe epilepsy (TLE). Despite the potentially life-threatening nature of the immediate post-ictal state, its neurobiological underpinnings remain understudied. We provide evidence in mice and humans that seizure-associated focal spreading depolarization (sSD) is a pathoclinical key factor in epilepsy. Using two-photon or widefield imaging (hippocampus, neocortex), field potential and single unit recordings, and behavioral assessment in mice, we first studied seizures during viral encephalitis, and subsequently established an optogenetic approach to dissociate hippocampal seizures and SD. We find region-specific occurrence of sSD that displays distinct spatial trajectories to preceding seizures, and show that seizure-related and isolated hippocampal SD prompt post-ictal wandering. This clinically relevant locomotor phenotype occurred in the absence of hippocampal SD progression to the neocortex. Finally, we confirm sSD existence in human epilepsy, in a patient cohort with refractory focal epilepsy, via Behnke-Fried electrode recordings. In this cohort, sSD displayed a similar temporomesial propensity as in mice. This work uncovers sSD as a previously underrecognized pathoclinical entity underlying postictal behavioral abnormalities in epilepsy. Our results carry wide-reaching ramifications for epilepsy research and neurology, and challenge current EEG-standards.

Regional associations of sleep architecture and Alzheimer's disease pathology
Objective: Recent evidence suggests that disturbances of sleep architecture are linked to Alzheimer's disease (AD) pathology. Here, we assessed the association between sleep architecture and regional amyloid and tau pathology employing a portable sleep-monitoring device in addition to PET imaging. Methods: 18 cognitively normal adults (CN; M(Age) = 64.06 (8.63), Sex (M/F) =6/12) and 18 patients with MCI/early AD (M(Age) = 67.33 (8.25), Sex (M/F) =9/9) were included from the 'Tau Propagation Over Time' (T-POT) study. All subjects underwent amyloid ([11C]-PiB) and tau ([18F]-AV1451) PET imaging. PET images were normalized to MNI-space and intensity standardized to the whole cerebellum ([11C]-PiB) or the inferior cerebellum ([18F]-AV1451). Sleep monitoring was performed at home using the portable 'Dreem' EEG-headband (Beacon Biosignal), which is a reliable and comfortable wireless alternative to the gold-standard polysomnography (PSG). Sleep recordings were performed within six months of the PET acquisitions. At least, one sufficient night had to be acquired, which was used to assess the sleep macrostructure for each individual. Total duration of sleep phases per minutes (i.e. REM, N1, N2, N3) and total sleep time were extracted. In a first step, a linear mixed model (LMM) was used to compare the groups in terms of duration of the different sleep stages across the nightly recordings. Given the results of this comparison, mean N1 and N3 duration were subsequently correlated with regional amyloid and tau pathology SUVRs of 34 cortical regions using Spearman's correlation. The reported results are based on one-tailed tests. All analyses were corrected for age. Results: Patients with MCI/AD showed reduced N3 duration (p = .007) compared to the CN group. A trend was observed indicating that patients with MCI/AD exhibited longer N1 durations (p = .094); however, this difference did not reach statistical significance. Shorter N3 duration was associated with higher regional amyloid load in the paracentral lobe and the posterior cingulate gyrus, whereas longer N1 duration was linked to higher amyloid pathology in several regions, including the medial temporal lobe, cingulate cortex and the occipital lobe. Moreover, associations were observed between longer N1 duration and greater tau burden in regions comprising the temporal lobe, cingulate cortex, and medial-frontal areas of the brain. Conclusion: Differences in sleep architecture between healthy controls and MCI/AD may arise from regionally-specific accumulation patterns of AD pathologies. Although it remains unknown whether disruptions in sleep architecture are a cause or a consequence, a complex relationship between AD-aggregation pathology in specific brain regions and the different phases of sleep appears to emerge.

Thermoceptive predictions and prediction errors in the anterior insula
Contemporary theories of interoception propose that the brain constructs a model of the body for predicting the states and allostatic needs of all organs, including the skin, and updates this model using prediction error signals. However, empirical tests of this proposal are scarce in humans. This computational neuroimaging study investigated the presence and location of thermoceptive predictions and prediction errors in the brain using probabilistic manipulations of skin temperature in a novel interoceptive learning paradigm. Using functional MRI in healthy volunteers, we found that a Bayesian model provided a better account of participants' skin temperature predictions than a non-Bayesian model. Further, activity in a network including the anterior insula was associated with trial-wise predictions and precision-weighted prediction errors. Our findings provide further evidence that the anterior insula plays a key role in implementing the brain's model of the body, and raise important questions about the structure of this model.

Genetic reduction of the translational repressors FMRP and 4E-BP2 preserves memory in mouse models of Alzheimer's disease
Alzheimer's disease (AD) is characterized by progressive memory decline. Converging evidence indicates that hippocampal mRNA translation (protein synthesis) is defective in AD. Here, we show that genetic reduction of the translational repressors, Fragile X messenger ribonucleoprotein (FMRP) or eukaryotic initiation factor 4E(eIF4E)-binding protein 2 (4E-BP2), prevented the attenuation of hippocampal protein synthesis and memory impairment induced by AD-linked amyloid-{beta} oligomers (A{beta}Os) in mice. Moreover, genetic reduction of 4E-BP2 rescued memory deficits in aged APPswe/PS1dE9 (APP/PS1) transgenic mouse model of AD. Our findings demonstrate that strategies targeting repressors of mRNA translation correct hippocampal protein synthesis and memory deficits in AD models. Results suggest that modulating pathways controlling brain mRNA translation may confer memory benefits in AD.

Muti-omics characterization reveals brain-wide disruption of synapses and region- and age-specific changes in neurons and glia in Sp4 mutant mice, a genetic model of schizophrenia and bipolar disorder
Schizophrenia and bipolar disorder are highly heritable mental illnesses with unclear pathophysiology. Heterozygous loss-of-function mutations of Sp4, a zinc-finger transcription factor, greatly increase risk of schizophrenia and bipolar disorder. To investigate the molecular functions of Sp4 in an unbiased manner in vivo, we performed multi-omics analyses of Sp4 mutant mice. Bulk and single nucleus RNA-seq data showed prominent gene expression changes in all brain regions and most cell types, including neuronal and non-neuronal cells. Gene set enrichment analysis of transcriptomic changes revealed alterations in many molecular pathways, including synapse, oxidative phosphorylation, and ribosome. Synapse proteomics of Sp4 mutants pointed to impaired glutamatergic signaling and altered presynaptic function. In Sp4 heterozygous mutant mice, prefrontal cortex and striatum exhibited downregulation of synapse pathways and neuronal hypoactivity at 1 month, associated with reduced sterol biosynthesis in astrocytes, whereas at 3 months, there was a shift to neuronal hyperactivity, concurrent with suppressed immune pathways in the striatal microglia. Furthermore, our study found that much of the transcriptomic changes might be accounted for by a set of transcription regulators (Nr3c1, Creb1, and Kdm5b) under the control of Sp4. Overall, this study provides cellular and molecular features resulting from Sp4 LoF that may explain the pathophysiology of SCZ-BD psychotic disorder spectrum.

Functional contribution of astrocytic Kir4.1 channels to spasticity after spinal cord injury
Spasticity, a prevalent motor issue characterized by network hyperexcitability, causes pain and discomfort, with existing treatments offering limited relief. While past research has focused on neuronal factors, the role of astrocytes in spasticity has been overlooked. This study explores the potential of restoring astrocytic potassium (K+) uptake to reduce spasticity following SCI. Astrocytes buffer extracellular K+ via Kir4.1 channels, preventing neuronal hyperexcitability. Following spinal cord injury (SCI), Kir4.1 levels decrease at the injury site, though the consequences and mechanisms of this reduction within the motor output area have not been investigated. Utilizing advanced techniques, we demonstrate that lumbar astrocytes in a juvenile thoracic SCI mouse model switch to reactive phenotype, displaying morpho-functional and pro-inflammatory changes. These astrocytes also experience NBCe1-mediated intracellular acidosis, leading to Kir4.1 dysfunction and impaired K+ uptake. Enhancing Kir4.1 function reduces spasticity in SCI mice, revealing new therapeutic targets for neurological diseases associated with neuronal hyperexcitability.

RiboTag RNA Sequencing Identifies Local Translation of HSP70 In Astrocyte Endfeet After Cerebral Ischemia
Brain ischemia causes disruption in cerebral blood flow and blood-brain barrier (BBB) integrity which are normally maintained by the astrocyte endfeet. Emerging evidence points to dysregulation of the astrocyte translatome during ischemia, but its effects on the endfoot translatome are unknown. In this study, we aimed to investigate the early effects of ischemia on the astrocyte endfoot translatome in a rodent model of cerebral ischemia-reperfusion. To do so, we immunoprecipitated astrocyte-specific tagged ribosomes (RiboTag IP) from mechanically isolated brain microvessels. In mice subjected to middle cerebral artery occlusion and reperfusion and contralateral controls, we sequenced ribosome-bound RNAs from perivascular astrocyte endfeet and identified 205 genes that were differentially expressed in the translatome after ischemia. Pathways associated with the differential expressions included proteostasis, inflammation, cell cycle, and metabolism. Transcription factors whose targets were enriched amongst upregulated translating genes included HSF1, the master regulator of the heat shock response. The most highly upregulated genes in the translatome were HSF1-dependent Hspa1a and Hspa1b, which encode the inducible HSP70. We found that HSP70 is upregulated in astrocyte endfeet after ischemia, coinciding with an increase in ubiquitination across the proteome. These findings suggest a robust proteostasis response to proteotoxic stress in the endfoot translatome after ischemia. Modulating proteostasis in endfeet may be a strategy to preserve endfeet function and BBB integrity after ischemic stroke.

Amplification of olfactory transduction currents implements sparse stimulus encoding
Sensory systems must perform the dual and opposing tasks of being sensitive to weak stimuli while also maintaining information content in dense and variable sensory landscapes. This occurs in the olfactory system, where OSNs are highly sensitive to low concentrations of odors and maintain discriminability in complex odor environments. How olfactory sensory neurons (OSNs) maintain both sensitivity and sparsity is not well understood. Here, we investigated whether the calcium-activated chloride channel, TMEM16B, may support these dual roles in OSNs. We used multiphoton microscopy to image the stimulus-response density of OSNs in the olfactory epithelium. In TMEM16B knockout mice, we found that sensory representations were denser, and the magnitude of OSN responses was increased. Behaviorally, these changes in sensory representations were associated with an increased aversion to the odorant trimethylamine, which switches perceptual valence as its concentration increases, and a decreased efficiency of olfactory-guided navigation. Together, our results indicate that the calcium-activated chloride channel TMEM16B sparsens sensory representations in the peripheral olfactory system and contributes to efficient integrative olfactory-guided behaviors.

Reward-driven cerebellar climbing fiber activity influences both neural and behavioral learning
The cerebellum plays a key role in motor coordination and learning. In contrast with classical supervised learning models, recent work has revealed that CFs can signal reward-predictive information in some behaviors. This raises the question of whether CFs may also operate according to principles similar to those described by reinforcement learning models. To test how CFs operate during reward-guided behavior, and evaluate the role of reward-related CF activity in learning, we have measured CF responses in Purkinje cells of the lateral cerebellum during a Pavlovian task using 2-photon calcium imaging. Specifically, we have performed multi-stimulus experiments to determine whether CF activity meets the requirements of a reward prediction error (rPE) signal for transfer from an unexpected reward to a reward-predictive cue. We find that once CF activity is transferred to a conditioned stimulus, and there is no longer a response to reward, CFs cannot generate learned responses to a second conditioned stimulus that carries the same reward prediction. In addition, by expressing the inhibitory opsin GtACR2 in neurons of the inferior olive, and optically inhibiting these neurons across behavioral training at the time of unexpected reward, we find that the transfer of CF signals to the conditioned stimulus is impaired. Moreover, this optogenetic inhibition also impairs learning, resulting in a deficit in anticipatory lick timing. Together, these results indicate that CF signals can exhibit several characteristics in common with rPEs during reinforcement learning, and that the cerebellum can harness these learning signals to generate accurately timed motor behavior.

A preserved neural code for temporal order between memory formation and recall in the human medial temporal lobe
Temporal memory enables us to remember the temporal order of events happening in our life. The human medial temporal lobe (MTL) appears to contain neural representations supporting temporal memory formation, but the cellular mechanisms that preserve temporal order information for recall are largely unknown. Here, we examined whether human MTL neuronal activity represents the temporal position of events during memory formation and recall, using invasive single and multi-unit recordings in human epilepsy patients (n = 19). Participants freely navigated a virtual environment in order to explore and remember locations and temporal positions of objects. During each exploration period, they sequentially encountered two or three different objects, placed in different locations. This allowed us to examine single- and multi-unit neuronal firing rates (FR) as a function of the temporal position the objects were presented in. We found that a significant number of multi-units and single-units in various MTL regions including the hippocampus showed selectivity to the temporal position of objects during the exploration period. During recall, patients were asked to indicate which one of two objects from the same trial was found latter. Neural firing rates during recall showed a selectivity supporting recall of temporal positions. Interestingly, most of the selective single-units that stayed selective during encoding and recall preserved their temporal position preference. Our results thus suggest that neuronal activity in the human MTL contains a preserved neural code for temporal order in memory formation and recall.

Dnajc3 (HSP40) Modulates Axon Regeneration in the Mouse Optic Nerve
The present study is designed to identify the genes modulating optic nerve regeneration in the mouse. Using the BXD mouse strains as a genetic mapping panel, we examined differential responses to axon regeneration in order to map genomic loci modulating axonal regeneration. To study regeneration in the optic nerve, Pten was knocked down in the retinal ganglion cells using adeno-associated virus (AAV) delivery of an shRNA, followed by the induction of a mild inflammatory response by an intravitreal injection of Zymosan with CPT-cAMP. The axons of the retinal ganglion cells were damaged by optic nerve crush (ONC). Following a 12-day survival period, regenerating axons were labeled by Cholera Toxin B. Two days later, the regenerating axons within the optic nerve were examined to determine the number of regenerating axons and the distance traveled down the optic nerve. An integral genomic map was made using the regenerative response. Candidate genes were tested by knocking down expression using shRNA or by overexpressing the gene in AAV vectors. The analysis revealed a considerable amount of differential axonal regeneration across all 33 BXD strains, demonstrated by the number of axons regenerating and the length of the regenerating axons. Some strains (BXD99, BXD90, and BXD29) demonstrated significant axonal regeneration; while other strains (BXD13, BXD18, and BXD34) had very little axon regrowth. Within the regenerative data, there was a 4-fold increase in distance regenerated and a 7.5-fold difference in the number of regenerating axons. These data were used to map a quantitative trait locus modulating axonal regeneration to Chromosome 14 (115 to 119 Mb). Within this locus were 16 annotated genes. Subsequent testing revealed that one candidate gene, Dnajc3, modulates axonal regeneration. Knocking down of Dnajc3 led to a decreased regeneration response in the high regenerative strains (BXD90), while overexpression of Dnajc3 resulted in an increased regeneration response in C57BL/6J and a low regenerative strain (BXD34). In this study, Dnajc3 (encodes Heat Shock Protein 40, HSP40, a molecular chaperone) was identified as a modulator of axon regeneration in mice. Dnajc3 not only increases the number of regenerating axons, it also increases the distance the axons travel. If regeneration is to occur in large mammals, the distance that axons would have to travel to their target is considerably longer than that of the mouse. Thus, increasing the number of regenerating axons and the distance they travel may prove to be critical for functional regenerations in humans.

Improved optogenetic modification of the spiral ganglion neurons for future optical cochlear implants
Optogenetic stimulation has become a promising approach for restoring lost body function. For example, partial restoration of vision has been achieved in a blind patient and proof-of-concept has been demonstrated for optogenetic hearing restoration in rodents. In order to prepare clinical translation of hearing restoration, efficient and safe optogenetic modification of spiral ganglion neurons (SGNs) in the mature cochlea remains to be developed. Here, we established microcatheter-based administration adeno-associated virus (AAV) to scala tympani of the cochlea of Mongolian gerbils and compared it to the previously developed AAV-injection into the spiral ganglion. We probed the potential AAV-PHP.S capsid to express channelrhodopsins (ChRs) under the control of the human synapsin promotor in mature SGNs in hearing and deafened gerbils. Using the microcatheter approach, but not with the AAV-modiolus injection, we achieved reliable ChR expression in SGN enabling optogenetic stimulation of the auditory pathway in 80% of the treated animals. Yet, the efficiency of SGN transduction was modest with only ~30% ChR-expressing SGNs. Moreover, we encountered off-target expression in hair cells in hearing gerbils in both approaches, but not ChR expression in the central nervous system using microcatheter administration. Comparing optogenetic auditory brainstem responses of gerbils with and without hair cell transduction confirmed that SGNs were the primary site of optogenetic stimulation of the pathway.

Estimating the mean: behavioral and neural correlates of summary representations for time intervals
Our behavior is guided by the statistical regularities in the environment. Prior research on temporal context effects has demonstrated the dynamic processes through which humans adapt to the environment's temporal regularities. However, learning temporal regularities not only entails dynamic adaptation to traces of previous individual events but also often requires the extraction and retention of summary statistics (e.g., the mean) of temporal distributions. To investigate these summary representations for temporal distributions and to test their sensitivity to distributional changes, we explicitly asked participants to extract the mean of different distributions of time intervals, which shared the same mean but varied in their variability specifically operationalized by the width and presentation frequency of the intervals. Our findings showed that the variability of the estimated mean increased with the distributions' variability, even though the actual mean remained constant. We further examined how such learning of temporal distributions modulates EEG signals during subsequent temporal judgments. Analysis revealed that the contingent negative variation (CNV), predictive of single-trial RTs, was correlated with how much individuals' estimates of the mean were affected by the distributions' variability. Conversely, the post-interval P2 was not modulated by the distributions but predicted participants' responses, suggesting that P2 reflects the perceived duration of an interval. Taken together, our results demonstrate not only that humans can accurately estimate the mean of a temporal distribution, but also that the representation of the mean becomes more uncertain as the variability of the distribution increases, as reflected neurally in the preparation-related CNV during temporal decisions.

Pre-fusion AAA+ remodeling of target-SNARE protein complexes enables synaptic transmission
Membrane fusion is driven by SNARE complex formation across cellular contexts, including vesicle fusion during synaptic transmission. Multiple proteins organize trans-SNARE complex assembly and priming, leading to fusion. One target membrane SNARE, syntaxin, forms nanodomains at the active zone, and another, SNAP-25, enters non-fusogenic complexes with it. Here, we show that the AAA+ protein NSF (N-ethylmaleimide sensitive factor) and SNAP (soluble NSF attachment protein) must act prior to fusion. We show that syntaxin clusters are conserved, that NSF colocalizes with them, and characterize SNARE populations within and near these clusters using cryo-EM. Supercomplexes of NSF, alpha;-SNAP, and either a syntaxin tetramer or two binary complexes of syntaxin - SNAP-25 reveal atomic details of SNARE processing and show how sequential ATP hydrolysis drives disassembly. These results suggest a functional role for syntaxin clusters as reservoirs and a corresponding role for NSF in syntaxin liberation and SNARE protein quality control preceding fusion.

Neuroanatomy of the Accessory Olfactory Bulb in the Fossorial Water Vole
The accessory olfactory bulb (AOB) plays a key role in processing chemical signals crucial for species-specific social and reproductive behaviors. While extensive research has focused on the vomeronasal system of laboratory rodents, less is known about wild species, particularly those that rely heavily on chemical communication. This study aims to characterize the morphological and neurochemical organization of the AOB in the fossorial water vole (Arvicola scherman), a subterranean rodent species from the family Cricetidae. We have employed histological techniques, including Nissl and hematoxylin staining, as well as immunohistochemical and lectin-histochemical markers, to assess the AOB structure. Our findings reveal that the AOB of the water vole exhibits a distinct laminar organization with prominent mitral cells in the mitral-plexiform layer, as well as dense labeling of periglomerular and short-axon cells in the glomerular layer. Lectin histochemistry further confirmed zonation patterns analogous to those seen in other rodent species. Immunohistochemical analysis demonstrated significant expression of PGP 9.5, suggesting its involvement in maintaining neuronal activity within the AOB. In contrast, the absence of SMI-32 labeling in the AOB, compared to its strong expression in the main olfactory bulb, highlights functional distinctions between these two olfactory subsystems. These structural and neurochemical characteristics suggest that the AOB of the fossorial water vole is adapted for enhanced processing of chemosensory signals, which may play a pivotal role in its subterranean lifestyle. Our results provide a foundation for future studies exploring the functional implications of these adaptations, including potential improvements in the integrated management of these vole populations.

Traveling Waves in the Human Visual Cortex: a MEG-EEG Model-Based Approach
Brain oscillations might be traveling waves propagating in cortex. Studying their propagation within single cortical areas has mostly been restricted to invasive measurements. Their investigation in healthy humans, however, requires non-invasive recordings, such as MEG or EEG. Identifying traveling waves with these techniques is challenging because source summation, volume conduction, and low signal-to-noise ratios make it difficult to localize cortical activity from sensor responses. The difficulty is compounded by the lack of a known ground truth in traveling wave experiments. Rather than source-localizing cortical responses from sensor activity, we developed a two-part model-based neuroimaging approach: (1) The putative neural sources of a propagating oscillation were modeled within primary visual cortex (V1) via retinotopic mapping from functional MRI recordings (encoding model); and (2) the modeled sources were projected onto MEG and EEG sensors to predict the resulting signal using a biophysical head model. We tested our model by comparing its predictions against the MEG-EEG signal obtained when participants viewed visual stimuli designed to elicit either fovea-to-periphery or periphery-to-fovea traveling waves or standing waves in V1, in which ground truth cortical waves could be reasonably assumed. Correlations on within-sensor phase and amplitude relations between predicted and measured data revealed good model performance. Crucially, the model predicted sensor data more accurately when the input to the model was a traveling wave going in the stimulus direction compared to when the input was a standing wave, or a traveling wave in a different direction. Furthermore, model accuracy peaked at the spatial and temporal frequency parameters of the visual stimulation. Together, our model successfully recovers traveling wave properties in cortex when they are induced by traveling waves in stimuli. This provides a sound basis for using MEG-EEG to study endogenous traveling waves in cortex and test hypothesis related with their role in cognition.

Reduction of SynGAP-γ, disrupted splicing of Agap3, and oligodendrocyte deficits in Srrm2 mice, a genetic model of schizophrenia and neurodevelopmental disorder
Rare loss-of-function (LoF) variants in SRRM2, which encodes the SRRM2 splicing factor, are associated with schizophrenia and a neurodevelopmental disorder. How haploinsufficiency of SRRM2 leads to brain dysfunction is unknown. We find that Srrm2+/- mice display (i) large-scale changes in gene expression in neuronal and glial cells, affecting synapse-related and other common molecular pathways across multiple brain regions, (ii) reduction of multiple key postsynaptic proteins, including the gamma isoform of SynGAP, itself encoded by a neurodevelopmental disorder risk gene, (iii) abnormal splicing and elevated expression of Agap3, a SynGAP interactor, (iv) reduced numbers of oligodendrocytes accompanied by decreased expression of myelin-related mRNAs and proteins, and (v) behavioral and EEG abnormalities, including reduction in sleep spindles that phenocopy humans with schizophrenia. Our findings provide insights into the molecular and neurobiological mechanisms of and potential therapeutic avenues for schizophrenia and the SRRM2 LoF neurodevelopmental disorder.

Anatomical and functional organization of the interpeduncular nucleus in larval zebrafish
The habenulo-interpeduncular pathway is a highly conserved neural circuit across vertebrates, but the anatomical and functional architecture of the interpeduncular nucleus (IPN) remains poorly understood. Here, we use a combination of immunohistochemistry, volumetric electron microscopy (EM), and two-photon imaging to provide the first detailed characterization of the internal organization of the IPN in larval zebrafish. We show that the IPN receives extensive projections from the tegmentum, and reveal a strict segregation between the dorsal (dIPN) and ventral (vIPN) subcircuits, with minimal cross-communication. In the dIPN, we characterise in detail the inputs and outputs of r1 pi neurons, which have been recently identified as representing the animal's heading direction. In the vIPN, we identify six distinct glomerular structures, each exhibiting specific patterns of reciprocal connections and projection pathways. Finally, we demonstrate that the connectivity and spontaneous activity patterns of habenular axons are shaped by the local anatomical features of the IPN, suggesting a role for the local interneurons in modulating presynaptic dynamics. Together, these results enhance our understanding of the internal organization of the IPN, and provide a framework for future investigations into both its physiology and its involvement in behavior.

Astrocyte regional specialization is shaped by postnatal development
Astrocytes are an abundant class of glial cells with critical roles in neural circuit assembly and function. Though many studies have uncovered significant molecular distinctions between astrocytes from different brain regions, how this regionalization unfolds over development is not fully understood. We used single-nucleus RNA sequencing to characterize the molecular diversity of brain cells across six developmental stages and four brain regions in the mouse and marmoset brain. Our analysis of over 170,000 single astrocyte nuclei revealed striking regional heterogeneity among astrocytes, particularly between telencephalic and diencephalic regions, at all developmental time points surveyed in both species. At the stages sampled, most of the region patterning was private to astrocytes and not shared with neurons or other glial types. Though astrocytes were already regionally patterned in late embryonic stages, this region-specific astrocyte gene expression signature changed dramatically over postnatal development, and its composition suggests that regional astrocytes further specialize postnatally to support their local neuronal circuits. Comparing across species, we found divergence in the expression of astrocytic region- and age-differentially expressed genes and the timing of astrocyte maturation relative to birth between mouse and marmoset, as well as hundreds of species differentially expressed genes. Finally, we used expansion microscopy to show that astrocyte morphology is largely conserved across gray matter forebrain regions in the mouse, despite substantial molecular divergence.

Hand Position Fields of Neurons in the Premotor Cortex of Macaques during Natural Reaching
Planning and execution for goal-directed movements requires the integration of the current position of body or body parts with various kinematic parameters of the movement itself. In the hippocampus, the field-based representation of spatial information plays an essential role in this process during navigation. However, if a similar, field-based encoding framework is also utilized by the motor areas during hand reaching remains unclear. In this study, we investigated the hand position tuning in the dorsal premotor cortex (PMd) neurons (n = 601) when four monkeys performing a naturalistic reach-and-grasp task. We show that 132/601 (22%) of PMd neurons increased their firing rates when the monkey's hand occupied specific positions in the space, forming the "position fields" in their spatial firing maps that can be well described by 2D Gaussian functions/kernels. We further analyzed how the field-tuning of hand position is co-represented with other task-related parameters including the hand moving direction, speed, and reward location in the same population of PMd neurons, revealing a mixed-selective framework also similar to that discovered in the hippocampus. These position-tuned cells demonstrated high efficiency in encoding hand position, with ~10% of overall recorded neurons contributing >80% of accuracy in decoding instantaneous hand moving trajectories. These results suggest that a field-based encoding framework of position may be a common component to representing spatial information and integrating it with kinematic parameters for guiding goal-directed movements of the body or body parts.

Neuronal overexpression of potassium channel subunit Kcnn1 prolongs survival of SOD1-linked ALS and A53T alpha-synuclein mouse models
Eye muscles and the motor neurons in the innervating cranial nerve nuclei are relatively spared in human ALS, and likewise, these cranial motor neurons are spared of SOD1YFP aggregation in a transgenic mouse model of SOD1 linked ALS, G85R SOD1YFP. RNA profiling of mouse oculomotor (CN3) neurons (resistant) vs hypoglossal (CN12) and spinal cord motor neurons (susceptible) from nontransgenic mice identified differentially expressed channel and receptor genes. A number were evaluated for effects on survival of the ALS strain by transgenesis or knockout to emulate the relative RNA level in oculomotor neurons. Transgenesis of Thy1.2-driven cDNA for mouse Kcnn1, a potassium channel subunit, extended the median days of survival time to paralysis of mutant G85R SOD1YFP mice by up to 100%, associated with absence of fluorescent aggregates; extended the median time to paralysis of G93A SOD1 mice by up to 55%; and extended the median time to endstage motor disease of a Thy1.2-driven alpha-synuclein transgenic strain by up to greater than 100%. The overexpressed Kcnn1 subunit was diffusely cytoplasmic in motor neurons and found to induce a multifaceted stress response as judged by RNAseq and immunostaining, including ER stress response, mitochondrial stress response, and an integrated stress response. Like other potassium channel subunits, Kcnn1 subunit is likely targeted to the ER, but as reported earlier in rodent Kcnn1-transfected cultured cells, in the absence of Kcnn2 with which to co-assemble, Kcnn1 is channel-inactive and is diffusely cytoplasmic. Thus, a nonassembled and potentially misfolded state of overexpressed Kcnn1 targeted to the ER of neurons may explain the stress responses, which in the mutant SOD1 and A53T alpha-synuclein mice, protect against the pathogenic proteins.

Cocaine taking and craving produce distinct transcriptional profiles in dopamine neurons
Dopamine (DA) signaling plays an essential role in reward valence attribution and in encoding the reinforcing properties of natural and artificial rewards. The adaptive responses from midbrain dopamine neurons to artificial rewards such as drugs of abuse are therefore important for understanding the development of substance use disorders. Drug-induced changes in gene expression are one such adaptation that can determine the activity of dopamine signaling in projection regions of the brain reward system. One of the major challenges to obtaining this understanding involves the complex cellular makeup of the brain, where each neuron population can be defined by a distinct transcriptional profile. To bridge this gap, we have adapted a virus-based method for labeling and capture of dopamine nuclei, coupled with nuclear RNA-sequencing, to study the transcriptional adaptations, specifically, of dopamine neurons in the ventral tegmental area (VTA) during cocaine taking and cocaine craving, using a mouse model of cocaine intravenous self-administration (IVSA). Our results show significant changes in gene expression across non-drug operant training, cocaine taking, and cocaine craving, highlighted by an enrichment of repressive epigenetic modifying enzyme gene expression during cocaine craving. Immunohistochemical validation further revealed an increase of H3K9me3 deposition in DA neurons during cocaine craving. These results demonstrate that cocaine-induced transcriptional adaptations in dopamine neurons vary by phase of self-administration and underscore the utility of this approach for identifying relevant phase-specific molecular targets to study the behavioral course of substance use disorders.

Predicting and phase targeting brain oscillations in real-time
Objective: Closed-loop neurostimulation (CLNS) procedures, aligning stimuli with electrical brain activity, are quickly gaining popularity in neuroscience. They have been employed to reveal causal links between neural activity patterns and function, and to explore therapeutic effects of electroencephalography (EEG-)guided stimulations during sleep. Most CLNS procedures are developed for a single purpose, detecting one specific pattern of interest in the EEG. Furthermore, most procedures have limited, if any, flexibility to adapt to temporal or interindividual variance in the signal, which means they wouldn't work optimally across the full physiological phenomenology. Approach: Here we present a new approach to CLNS, based on real-time signal modelling to predict brain activity, allowing targeting of a broad variety of oscillatory dynamics. Intrinsic to the modelling approach is adaptation to signal variance, such that no personalization steps prior to use are necessary. We systematically assess stimulus targeting performance of modelling-based CLNS (M-CLNS), across a wide range of brain oscillation frequencies and phases in human and rodent neurophysiological signals. Main results: Our results show high performance for all target phases and frequency bands, including slow oscillations, theta and alpha waves. Significance: These findings highlight the general applicability and adaptability of M-CLNS, which also favors its application in populations with an atypical oscillatory signature, like clinical or elderly populations. In conclusion, M-CLNS provides a promising new tool for neural activity-dependent stimulation in both experimental research and therapeutic applications, such as enhancing deep sleep in patients with sleep disorders.

Recovery from Spreading Depolarization is slowed by aging and accelerated by antioxidant treatment in locusts
Spreading depolarization (SD) temporarily shuts down neural processing in nervous systems with effective blood brain barriers. In mammals this is usually pathological in response to energetic stress. In insects a very similar process is induced by abiotic environmental stressors and can be beneficial by conserving energy. Age is a critical factor for predicting the consequences of SD in humans. We investigated the effect of aging on SD in an insect model of SD and explored the contribution of oxidative stress. Aging slowed the recovery of intact locusts from asphyxia by water submersion. In semi-intact preparations we monitored SD by recording the DC potential across the blood brain barrier in response to bath application of the Na+/K+-ATPase inhibitor, ouabain. Treatment with ouabain induced changes to the DC potential that could be separated into two distinct components: a slow, permanent negative shift, similar to the negative ultraslow potential recorded in mammals and human patients, as well as rapid, reversible negative DC shifts (SD events). Aging had no effect on the slow shift but increased the duration of SD events from ~0.6 minutes in young locusts to ~0.9 minutes in old ones. This was accompanied by a decrease in the rate of recovery of DC potential at the end of the SD event, from ~1.5 mV/s (young) to ~0.6 mV/s (old). An attempt to generate oxidative stress using rotenone was unsuccessful, but pretreatment with the antioxidant, N-acetylcysteine amide, had opposite effects to those of aging, reducing duration (control ~1.1 minutes, NACA ~0.7 minutes) and increasing rate of recovery (control ~0.5 mV/s, NACA ~1.0 mV/s) suggesting that it prevented oxidative damage occurring during the ouabain treatment. The antioxidant also reduced the rate of the slow negative shift. We propose that the aging locust nervous system is more vulnerable to stress due to a prior accumulation of oxidative damage. Our findings also strengthen the notion that insects provide useful models for the investigation of cellular and molecular mechanisms underlying SD in mammals.

Deep generative networks reveal the tuning of neurons in IT and predict their influence on visual perception
Finding the tuning of visual neurons has kept neuroscientists busy for decades. One approach to this problem has been to test specific hypotheses on the relevance of a visual property (e.g. orientation or color), build a set of 'artificial' stimuli that vary along that property and then record neural responses to those stimuli. Here, we present a complementary, data-driven method to retrieve the tuning properties of visual neurons. Exploiting deep generative networks and electrophysiology in monkeys, we first used a method to reconstruct any stimulus from its evoked neuronal activity in the inferotemporal cortex (IT). Then, by arbitrarily perturbing the response of individual cortical sites in the model, we generated naturalistic and interpretable sequences of images that strongly influence neural activity of that site. This method enables the discovery of previously unknown tuning properties of high-level visual neurons that are easily interpretable, which we tested with carefully controlled stimuli. When we knew which images drove the neurons, we activated the cells with electrical microstimulation and observed a predicable shift of the monkey perception in the direction of the preferred image. By allowing the brain to tell us what it cares about, we are no longer limited by our experimental imagination.

Integration of spatial transcriptomics with immunofluorescence staining reveals spatial heterogeneity and plasticity of astrocytes in experimental glioblastomas
Astrocytes comprise ~50% of all brain cells and present distinct morphological, molecular and functional properties in different brain regions. In glioblastoma (GBM), an aggressive primary brain tumour, tumour-associated astrocytes (TAAs) become activated and exhibit different transcriptomic profiles, morphology and functions supporting disease progression. Heterogeneity and specific roles of TAAs within various regions of tumours are poorly known. Advancements of single-cell and spatial transcriptomics allow to profile tumours at unprecedented resolution revealing cell phenotypes, hidden functionalities and spatial architecture in disease-specific context. We combined spatial transcriptomics and multiple immunofluorescent staining to visualize TAAs heterogeneity and location of various subpopulations in intracranial murine gliomas. Using distinct gene expression profiles, we identified subtypes of TAAs with distinct localization and inferred their specialized functionalities. Gene signatures associated with TAAs reflected their reprograming in the tumour microenvironment (TME), revealed their multiple roles and potential contributing factors shaping the local milieu. Using spatial correlation analysis of the spots, we inferred the interactome of Slc1a2 (encoding a glutamate transporter) with the other markers of TAAs based on segregated areas of the tumour. The designer RGD peptide blocking tumour-microglia communications, alters the spatial distribution of TAAs in experimental gliomas providing insights into potential mechanisms. Spatial transcriptomics combined with multiple staining unveils multiple functional phenotypes of TAAs and interactions within TME. It shows their distinct morphology and unveils different roles in various regions of the tumour. We demonstrate the glioma-induced heterogeneity of TAAs and their adaption to the pharmacologically-induced modification of the immunosuppressive TME.

Astrocytic HIV-1 Nef expression decreases glutamate transporter expression in the nucleus accumbens and increases cocaine-seeking behavior in rats
Cocaine use disorder is an intersecting issue in populations with HIV-1, further exacerbating the clinical course of the disease, contributing to neurotoxicity and neuroin-flammation. Cocaine and HIV neurotoxins play roles in neuronal damage during neuroHIV progression by disrupting glutamate homeostasis in the brain. Even with cART, HIV-1 Nef, an early viral protein expressed in approximately 1% of infected astrocytes, remains a key neurotoxin. This study investigates the relationship that exists between Nef, glutamate homeostasis, and cocaine in the NAc, a critical brain region associated with drug motiva-tion and reward. Using a rat model, we compared the effects of astrocytic Nef and cocaine by molecular analysis of glutamate transporters in the NAc. We further conducted be-havioral assessments for cocaine self-administration to evaluate cocaine-seeking behavior. Our findings indicate that both cocaine and Nef independently decrease the expression of the glutamate transporter GLT-1 in the NAc. Additionally, rats with astrocytic Nef ex-pression exhibited increased cocaine-seeking behavior but demonstrated sex dependent molecular differences after behavioral paradigm. In conclusion, our results suggest the expression of Nef intensifies cocaine-induced alterations in glutamate homeostasis in the NAc, potentially underlying increased cocaine-seeking. Understanding these interactions better may inform therapeutic strategies for managing cocaine use disorder in HIV-infected individuals.

Optical coherence tomography enables longitudinal evaluation of cell graft-directed remodeling in stroke lesions
Stem cell grafting can promote glial repair of adult stroke injuries during the subacute wound healing phase, but graft survival and glial repair outcomes are perturbed by lesion severity and mode of injury. To better understand how stroke lesion environments alter the functions of cell grafts, we employed optical coherence tomography (OCT) to longitudinally image mouse cortical photothrombotic ischemic strokes treated with allogeneic neural progenitor cell (NPC) grafts. OCT angiography, signal intensity, and signal decay resulting from optical scattering were assessed at multiple timepoints across two weeks in mice receiving an NPC graft or an injection of saline at two days after stroke. OCT scattering information revealed pronounced axial lesion contraction that naturally occurred throughout the subacute wound healing phase that was not modified by either NPC or saline treatment. By analyzing OCT signal intensity along the coronal plane, we observed dramatic contraction of the cortex away from the imaging window in the first week after stroke which impaired conventional OCT angiography but which enabled the detection of NPC graft-induced glial repair. There was moderate, but variable, NPC graft survival at photothrombotic strokes at two weeks which was inversely correlated with acute stroke lesion sizes as measured by OCT prior to treatment, suggesting a prognostic role for OCT imaging and reinforcing the dominant effect of lesion size and severity on graft outcome. Overall, our findings demonstrate the utility of OCT imaging for both tracking and predicting natural and treatment-directed changes in ischemic stroke lesion cores.

Characteristics of spatial summation in the magnocellular, parvocellular, and koniocellular pathways
In this study, we characterize the spatial summation properties of targeted magnocellular, parvocellular, and koniocellular pathways within the central 20 degrees of visual field using chromatic transformations in DKL color space. For the magnocellular and koniocellular conditions, critical areas of complete spatial summation were found for all eccentricities. For the parvocellular conditions, complete spatial summation was absent within the stimulus size ranges tested. We also describe an anatomically and physiologically motivated model of receptive field pooling using probability summation. Model simulations suggest that the critical area of summation can be explained by the dendritic field size of underlying retinal ganglion cells, corroborating our psychophysical data.

Mitochondrial Dysfunction in Alzheimer's Disease Is Driven By Excess ER-Calcium Release in Patient-Derived Neurons
Tight regulation of mitochondrial Ca2+ is essential for neuronal bioenergetics and cellular metabolism. Ca2+ transfer from ER-localized ryanodine receptors (RyR) and inositol triphosphate receptors (IP3R) to the mitochondria maintains a steady Ca2+ source that fuels oxidative phosphorylation and ATP production. In Alzheimer's disease (AD), RyR-evoked Ca2+ release is markedly increased, contributing to synaptic deficits, protein mishandling, and memory impairment. Here, we demonstrate that dysregulated RyR-Ca2+ release directly compromises mitochondrial activity and is an early contributor to AD cellular pathology. We measured an array of mitochondrial functions using fluorescent biosensors and optical imaging in RyR2-expressing HEK cells and iPSC-derived neurons from familial AD and nonAD patients. In neurons from AD patients, resting mitochondrial Ca2+ levels were elevated alongside increased free radical production and higher caspase-3 activity relative to nonAD neurons. RyR-evoked Ca2+ release further potentiated pathogenic mitochondrial responses in AD neurons, with increased Ca2+ uptake and exaggerated membrane depolarization. Additionally, clearance of damaged mitochondria was impaired in AD neurons, demonstrating consequences from dysfunctional lysosomes. Notably, impairments to mitochondria in AD neurons were largely prevented with the RyR negative allosteric modulator, Ryanodex. These findings highlight how excess RyR-Ca2+ release broadly contributes to early cellular pathology in AD which includes a cascade of ER, lysosomal, and mitochondrial deficits culminating in neuronal decline and degeneration. Additionally, pharmacological suppression of RyR-Ca2+ release preserves mitochondrial, ER and lysosomal function, thus providing a novel and effective therapeutic.

Melanocortin 4 Receptor-Dependent Mechanism of ACTH in Preventing Anxiety-Like Behaviors and Normalizing Astrocyte Proteins After Early Life Seizures
Epilepsy, affecting millions globally, often leads to significant cognitive and psychiatric comorbidities, particularly in children. Anxiety and depression are particularly prevalent, with roughly a quarter of pediatric epilepsy patients having a comorbid diagnosis. Current treatments inadequately address these issues. Adrenocorticotropic hormone (ACTH), a melanocortin peptide, has shown promise in mitigating cognitive deficits after early life seizures (ELS), potentially through mechanisms beyond its canonical action on melanocortin 2 receptor (MC2R). This study explores the hypothesis that recurrent ELS is associated with long-term anxiety, and that treatment with ACTH can prevent this anxiety through a mechanism that involves melanocortin 4 receptors (MC4R) in the brain. Our findings reveal that ACTH ameliorates anxiety-like behavior associated with ELS, without altering seizure parameters, in wildtype (WT) mice but not in MC4R knockout (KO) mice. Our findings also show that knocking-in MC4R in either neurons or astrocytes was able to rescue the anxiety-like behavior after ACTH treatment. Further, our results show that ACTH normalizes important astrocytic proteins like Glial Fibrillary Acidic Protein (GFAP) and Aquaporin-4 (AQP4) after ELS. This suggests that ACTHs beneficial effects on anxiety are mediated through MC4R activation in both neuronal and astrocytic populations. This study underscores the therapeutic potential of targeting MC4R in epilepsy treatment, highlighting its role in mitigating cognitive impairments and anxiety-like behaviors associated with ELS.

A multi-omics and cell type-specific characterization of the ventral striatum in human cocaine use disorder
Epigenome, transcriptome, and proteome analyses of postmortem brains have revealed initial molecular insights into cocaine use disorder (CUD). However, the inter-relationship between these -omics and the contribution of individual cell types remain largely unknown. We present an in-depth analysis of molecular changes in the ventral striatum in CUD at multi-omics and single-cell resolution. Integrative multi-omics analyses of microRNA-seq, RNA-seq, and proteomics datasets in 41 individuals and single-nuclei RNA-seq in a subset of 16 individuals revealed conserved deregulation of metabolic pathways, oxidative phosphorylation, and glutamatergic signaling. Cell type-specific analyses identified inverse metabolic pathway deregulation patterns in glial and neuronal cells, notably in astrocytes and medium spiny neurons (MSNs). Characterizing astrocyte-neuron crosstalk revealed altered glutamatergic and cell adhesion signaling in CUD. By applying a comprehensive multi-omics analytical framework, our study provides novel insights into CUD-associated molecular changes in the ventral striatum, suggesting astrocytes, MSNs, and their crosstalk as particularly perturbed in CUD.

Cerebellar climbing fibers signal flexible, rapidly adapting reward predictions
Classical models of cerebellar computation posit that climbing fibers (CFs) operate according to supervised learning rules, correcting movements by signaling the occurrence of motor errors. However, recent findings suggest that in some behaviors, CF activity can exhibit features that resemble the instructional signals necessary for reinforcement learning, namely reward prediction errors (rPEs). Despite these initial observations, many key properties of reward-related CF responses remain unclear, thus limiting our understanding of how they operate to guide cerebellar learning. Here, we have measured the postsynaptic responses of CFs onto cerebellar Purkinje cells using two-photon calcium imaging to test how they respond to learned stimuli that either do or do not predict reward. We find that CFs can develop generalized responses to similar cues of the same modality, regardless of whether they are reward predictive. However, this generalization depends on temporal context, and does not extend across sensory modalities. Further, learned CF responses are flexible, and can be rapidly updated according to new reward contingencies. Together these results suggest that CFs can generate learned, reward-predictive responses that flexibly adapt to the current environment in a context-sensitive manner.

Reprogrammed Human Lateral Ganglionic Eminence Precursors Generate Striatal Neurons and Restore Motor Function in a Rat Model of Huntington's Disease.
BackgroundHuntingtons disease (HD) is a genetic neurological disorder predominantly characterised by the progressive loss of GABAergic medium spiny neurons in the striatum resulting in motor dysfunction. One potential strategy for the treatment of HD is the development of cell replacement therapies to restore neuronal circuitry and function by the replacement of lost neurons. We propose the generation of lineage-specific human lateral ganglionic eminence precursors (hiLGEP) using direct reprogramming technology provides a novel and clinically viable cell source for cell replacement therapy for HD.

MethodshiLGEPs were derived by direct reprogramming of adult human dermal fibroblasts (aHDFs) using chemically modified mRNA (cmRNA) and a defined reprogramming medium. hiLGEPs were differentiated in vitro using an optimised striatal differentiation medium. Acquisition of a striatal precursor and neural cell fate was assessed through gene expression and immunocytochemical analysis of key markers. hiLGEP-derived striatal neuron functionality in vitro was demonstrated by calcium imaging using Cal-520. To investigate the ability for hiLGEP to survive, differentiate and functionally integrate in vivo, we transplanted hiLGEPs into the striatum of quinolinic acid (QA)-lesioned rats and performed behavioural assessment using the cylinder test over the course of 14 weeks. Survival and differentiation of hiLGEPs was assessed at 8 and 14-weeks post-transplant by immunohistochemical analysis.

ResultsWe demonstrate the capability to generate hiLGEPs from aHDFs using cmRNA encoding the pro-neural genes SOX2 and PAX6, combined with a reprogramming medium containing Go6983, Y-27632, N-2 and Activin A. hiLGEPs generated functional DARPP32+ neurons following 14 days of culture in BrainPhys media supplemented with dorsomorphin and Activin A. We investigated the ability for hiLGEPs to survive transplantation, differentiate to medium spiny-like striatal neurons and improve motor function in the QA lesion rat model of HD. Fourteen weeks after transplantation, we observed STEM121+ neurons co-expressing MAP2, DARPP32, GAD65/67, or GABA. Rats transplanted with hiLGEPs also demonstrated reduction in motor function impairment as determined by spontaneous exploratory forelimb use when compared to saline transplanted animals.

ConclusionThis study provides proof-of-concept and demonstrates for the first time that aHDFs can be directly reprogrammed to hiLGEPs which survive transplantation, undergo neuronal differentiation to generate medium spiny-like striatal neurons, and reduce functional impairment in the QA lesion rat model of HD.

Significance statementThe present study reports for the first time that human lateral ganglionic eminence precursor (hiLGEP) cells directly reprogrammed from adult human fibroblasts using chemically modified mRNA can survive transplantation into the quinolinic acid-lesioned rat striatum and generate medium spiny striatal neurons. Most importantly, the authors show that transplantation of directly reprogrammed hiLGEPs restores motor function impairment by 14 weeks post-transplantation. This work provides proof of concept and demonstrates that directly reprogrammed hiLGEPs offer an effective and clinically viable cell source for cell replacement therapy to treat Huntingtons disease.

Distinct cortical spatial representations learned along disparate visual pathways
Recent experimental studies have discovered diverse spatial properties, such as head direction tuning and egocentric tuning, of neurons in the postrhinal cortex (POR) and revealed how the POR spatial representation is distinct from the retrosplenial cortex (RSC). However, how these spatial properties of POR neurons emerge is unknown, and the cause of distinct cortical spatial representations is also unclear. Here, we build a learning model of POR based on the pathway from the superior colliculus (SC) that has been shown to have motion processing within the visual input. Our designed SC-POR model demonstrates that diverse spatial properties of POR neurons can emerge from a learning process based on visual input that incorporates motion processing. Moreover, combining SC-POR model with our previously proposed V1-RSC model, we show that distinct cortical spatial representations in POR and RSC can be learnt along disparate visual pathways (originating in SC and V1), suggesting that the varying features encoded in different visual pathways contribute to the distinct spatial properties in downstream cortical areas.

Conflict of interest statementThe authors declare no competing financial interests.

Human BNST volume is not simply sexually dimorphic
The bed nucleus of the stria terminalis (BNST) is a sexually dimorphic basal forebrain region, is a claim prevalent across rodent and human neuroscience research, with particular emphasis on its substantially larger size in males. Despite the pervasiveness of this claim, with potential implications for understanding sex differences in anxiety and substance use disorders, inspection of prior literature reveals a complex and nuanced picture. Direct evidence for larger male BNST size in humans comes solely from a handful of mostly small-scale post-mortem studies, which show either no, moderate, or very large differences, therefore indicating the need for a larger systematic investigation. Addressing this, we developed a novel 3T T1-weighted (T1w) manual segmentation protocol of the BNST, which was applied to ultra-high resolution T1w structural MRI data in 170 young human adults. Using a Bayesian modelling approach, taking into account existing post-mortem data, and controlling for total brain volume, age, and sibship, we find little evidence for total BNST volume differences between males and females. We recommend that researchers exercise caution when reporting evidence of BNST sexual dimorphism, particularly when translating findings from rodent models in which the BNST may play a different, olfaction-focused, role.

The role of repetition in context-dependent preference
The context in which decisions are learned can influence what choices we prefer in new situations. Such dependencies are well replicated and often lead to decision biases, i.e. choices that deviate from rational choice theory. We propose a simple computational model of such biases. To test the model, we analyzed behavioral data from 351 male and female participants in a series of nine value-based decision tasks and re-analyze six previously published datasets (n = 350 participants). Our results show that the combination of two basic principles, learning by reward, and repetition of decisions, is sufficient to explain biased preferences across all 15 datasets. Using standard analysis and hierarchical Bayesian model comparison we found that the proposed model provides a better explanation than previous accounts. In addition, our results show that higher choice frequency is linked to higher subjective valuation and lower value uncertainty. Results indicate that repetition is an important mechanism in shaping preferences.

Significance StatementHuman decision-making often deviates from rational choice theory. Understanding how decision biases emerge is essential for interpreting real-world human behavior. Our study shows how repeating decisions can shape preference in novel situations. We adapt a simple computational model that can explain biased preferences based on reward learning and decision repetition. By testing the model across 15 datasets, we demonstrate that it outperforms previous models, also offering new insights into how preferences affect subjective valuation and uncertainty. In sum, these findings provide a deeper understanding of how context-dependent preferences emerge and persist.

Peripherally administered TNF inhibitor is not protective against α-synuclein-induced dopaminergic neuronal death in rats
The underlying cause of neuronal loss in Parkinsons disease (PD) remains unknown, but evidence implicates neuroinflammation in PD pathobiology. The pro-inflammatory cytokine soluble tumor necrosis factor (TNF) seems to play an important role and thus has been proposed as a therapeutic target for modulation of the neuroinflammatory processes in PD. In this regard, dominant-negative TNF (DN-TNF) agents are promising antagonists that selectively inhibit soluble TNF signaling, while preserving the beneficial effects of transmembrane TNF. Previous studies have tested the protective potential of DN-TNF-based therapy in toxin-based PD models. Here we test for the first time the protective potential of a DN-TNF therapeutic against -synuclein-driven neurodegeneration in the viral vector-based PD rat model. To do so, we administered the DN-TNF agent XPro1595 subcutaneously for a period of 12 weeks. In contrast to previous studies using different PD models, neuroprotection was not achieved by systemic XPro1595 treatment. -synuclein-induced loss of nigrostriatal neurons, accumulation of pathological inclusions and microgliosis was detected in both XPro1595- and saline-treated animals. XPro1595 treatment increased the percentage of the hypertrophic/ameboid Iba1+ cells in SN and reduced the striatal MHCII+ microglia in the striatum of -synuclein-overexpressing animals. However, the treatment did not prevent the MHCII upregulation seen in the SN of the model, nor the increase of CD68+ phagocytic cells. Therefore, despite an apparently positive immune effect, this did not suffice to protect against viral vector-derived -synuclein-induced neurotoxicity. Further studies are warranted to better elucidate the therapeutic potential of soluble TNF inhibitors in PD.

RIPK2 is crucial for the microglial inflammatory response to bacterial muramyl dipeptide but not to lipopolysaccharide
Receptor-interacting serine/threonine protein kinase 2 (RIPK2) is a kinase that plays an essential role in the modulation of innate and adaptive immune responses. As a downstream signaling molecule for nucleotide-binding oligomerization domain 1 (NOD1), NOD2, and Toll-like receptors (TLRs), it is implicated in the signaling triggered by recognition of microbe-associated molecular patterns by NOD1/2 and TLRs. Upon activation of these innate immune receptors, RIPK2 mediates the release of pro-inflammatory factors by activating mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-{kappa}B). However, whether RIPK2 is essential for downstream inflammatory signaling following the activation of NOD1/2, TLRs, or both remains controversial. In this study, we examined the role of RIPK2 in NOD2- and TLR4-dependent signaling cascades following stimulation of microglial cells with bacterial muramyl dipeptide (MDP), a NOD2 agonist, or lipopolysaccharide (LPS), a TLR4 agonist. We utilized a highly specific proteolysis targeting chimera (PROTAC) molecule, GSK3728857A, and found dramatic degradation of RIPK2 in a concentration- and time-dependent manner. Importantly, the PROTAC completely abolished MDP-induced increases in iNOS and COX-2 protein levels and pro-inflammatory gene transcription of Nos2, Ptgs2, Il-1{beta}, Tnf, Il6, Ccl2, and Mmp9. However, increases in iNOS and COX-2 proteins and pro-inflammatory gene transcription induced by the TLR4 agonist, LPS, were only slightly attenuated with the GSK3728857A pretreatment. Further findings revealed that the RIPK2 PROTAC completely blocked the phosphorylation and activation of p65 NF-{kappa}B and p38 MAPK induced by MDP, but it had no effects on the phosphorylation of these two mediators triggered by LPS. Collectively, our findings strongly suggest that RIPK2 plays an essential role in the inflammatory responses of microglia to bacterial MDP but not to LPS.

Neocortical differentiation and hippocampal integration of non-meaningful items and their spatial location
Resolving interference between similar inputs is a critical feature of adaptive memory systems. Computational theories of the medial temporal lobe posit that the dentate gyrus and CA3 (CA3DG) subfields of the hippocampus are ideally suited to reduce interference via a process called pattern separation. Whereas neocortical areas upstream of the hippocampus have been shown to play a role in content-specific (e.g., spatial or object-related) interference reduction, the CA3DG is traditionally viewed as a domain-general pattern separator. Recent work also drew attention to the role of frontal and parietal control areas in allocating resources according to task demands during mnemonic discrimination, exerting top-down control over the medial temporal lobe. However, extant evidence in humans is almost solely based on mnemonic discrimination tasks involving everyday items, potentially confounding retrieval processes with pattern separation. Here, we studied pattern separation in a "process-pure" manner, utilizing non-meaningful fractal images. We acquired full-brain high-resolution functional MRI data of 39 participants (mean age (SD) = 22.6 (2.4) years, 19 females) while they studied fractals with varying degrees of interference in either their spatial or object features. Building upon the idea that the repetition of a stimulus results in a diminished BOLD response in areas involved in the processing of that stimulus (repetition suppression), we expected that regions engaged in pattern separation of objects or locations would decrease their response to repetitions, but not to highly similar (interference-inducing) items. We found that the parahippocampal cortex contributes to interference reduction in the spatial domain, while the perirhinal cortex contributes to interference reduction in the object domain. The frontoparietal control network was recruited during the encoding of both object and location lures, and displayed strengthened within- and cross-network connectivity in response to lures. Contrary to our expectations, the CA3DG showed repetition suppression to both exact repetitions and highly similar lures, indicating a lack of sensitivity to small differences in interfering stimuli. Altogether, these results are in line with content-specific neocortical interference reduction in the medial temporal lobe, possibly orchestrated by the frontoparietal control network, but challenge the view of CA3DG as a universal pattern separator.

Ventral Striatum is Preferentially Correlated with the Salience Network Including Regions in Dorsolateral Prefrontal Cortex
The ventral striatum (VS) receives input from the cerebral cortex and is modulated by midbrain dopaminergic projections in support of processing reward and motivation. Here we explored the organization of cortical regions linked to the human VS using within-individual functional connectivity MRI in intensively scanned participants. In two initial participants (scanned 31 sessions each), seed regions in the VS were preferentially correlated with distributed cortical regions that are part of the Salience (SAL) network. The VS seed region recapitulated SAL network topography in each individual including anterior and posterior midline regions, anterior insula, and dorsolateral prefrontal cortex (DLPFC) - a topography that was distinct from a nearby striatal seed region. The region of DLPFC linked to the VS is positioned adjacent to regions associated with domain-flexible cognitive control. The full pattern was replicated in independent data from the same two individuals and generalized to 15 novel participants (scanned 8 or more sessions each). These results suggest that the VS forms a cortico-basal ganglia loop as part of the SAL network. The DLPFC is a neuromodulatory target to treat major depressive disorder. The present results raise the possibility that the DLPFC may be an effective neuromodulatory target because of its preferential coupling to the VS and suggests a path toward further personalization.

Integration of distinct cortical inputs to primary and higher order inhibitory cells of the thalamus
The neocortex controls its own sensory input in part through top-down inhibitory mechanisms. Descending corticothalamic projections drive GABAergic neurons of the thalamic reticular nucleus (TRN), which govern thalamocortical cell activity via inhibition. Neurons in sensory TRN are organized into primary and higher order (HO) subpopulations, with separate intrathalamic connections and distinct genetic and functional properties. Here, we investigated top-down neocortical control over primary and HO neurons of somatosensory TRN. Projections from layer 6 of somatosensory cortex evoked stronger and more state-dependent activity in primary than in HO TRN, driven by more robust synaptic inputs and potent T-type calcium currents. However, HO TRN received additional, physiologically distinct, inputs from motor cortex and layer 5 of S1. Thus, in a departure from the canonical focused sensory layer 6 innervation characteristic of primary TRN, HO TRN integrates broadly from multiple corticothalamic systems, with unique state-dependence, extending the range of mechanisms for top-down control.