bioRxiv Subject Collection: Neuroscience's Journal

Progressive lifespan modifications in the corpus callosum following a single juvenile concussion in male mice monitored by diffusion MRI
Introduction: The sensitivity of white matter (WM) in acute and chronic moderate-severe traumatic brain injury (TBI) has been established. In concussion syndromes, particularly in preclinical rodent models, there is lacking a comprehensive longitudinal study spanning the lifespan of the mouse. We previously reported early modifications to WM using clinically relevant neuroimaging and histological measures in a model of juvenile concussion at one month post injury (mpi) who then exhibited cognitive deficits at 12mpi. For the first time, we assess corpus callosum (CC) integrity across the lifespan after a single juvenile concussion utilizing diffusion MRI (dMRI). Methods: C57Bl/6 mice were exposed to sham or two severities of closed-head concussion (Grade 1, G1, speed 2 m/sec, depth 1mm; Grade 2, G2, 3m/sec, 3mm) using an electromagnetic impactor at postnatal day 17. In vivo diffusion tensor imaging was conducted at 1, 3, 6, 12 and 18 mpi (21 directions, b=2000 mm2/sec) and processed for dMRI parametric maps: fractional anisotropy (FA), axial (AxD), radial (RD) and mean diffusivity (MD). Whole CC and regional CC data were extracted. To identify the biological basis of altered dMRI metrics, astrocyte and microglia in the CC were characterized at 1 and 12 mpi by immunohistochemistry. Results: Whole CC analysis revealed altered FA and RD trajectories following juvenile concussion. Shams exhibited a temporally linear increase in FA with age while G1/G2 mice had plateaued FA values. G2 concussed mice exhibited high variance of dMRI metrics at 12mpi, which was attributed to the heterogeneity of TBI on the anterior CC. Regional analysis of dMRI metrics at the impact site unveiled significant differences between G2 and sham mice. The dMRI findings appear to be driven, in part, by loss of astrocyte process lengths and increased circularity and decreased cell span ratios in microglia. Conclusion: For the first time, we demonstrate progressive perturbations to WM of male mice after a single juvenile concussion across the mouse lifespan. The CC alterations were dependent on concussion severity with elevated sensitivity in the anterior CC that was related to astrocyte and microglial morphology. Our findings suggest that long-term monitoring of children with juvenile concussive episodes using dMRI is warranted, focusing on vulnerable WM tracts.

Sleep-Deep-Net learns sleep wake scoring from the end-user and completes each record in their style.
Sleep-wake scoring is a time-consuming, tedious but essential component of clinical and pre-clinical sleep research. Sleep scoring is even more laborious and challenging in rodents due to the smaller EEG amplitude differences between states and the rapid state transitions which necessitate scoring in shorter epochs. Although many automated rodent sleep scoring methods exist, they do not perform as well when scoring new data sets, especially those which involve changes in the EEG/EMG profile. Thus, manual scoring by expert scorers remains the gold-standard. Here we take a different approach to this problem by using a neural network to accelerate the scoring of expert scorers. Sleep-Deep-Net (SDN) creates a bespoke deep convolution neural network model for individual electroencephalographic or local-field-potential records via transfer learning of GoogleNet, by learning from a small subset of manual scores of each EEG/LFP record as provided by the end-user. SDN then automates scoring of the remainder of the EEG/LFP record. A novel REM scoring correction procedure further enhanced accuracy. SDN reliably scores EEG and LFP data and retains sleep-wake architecture in wild-type mice, in sleep induced by the hypnotic zolpidem, in a mouse model of Alzheimer's disease and in a genetic knock-down study, when compared to manual scoring. SDN reduced manual scoring time to 1/12. Since SDN uses transfer learning on each independent recording, it is not biased by previously scored existing data sets. Thus, we find SDN performs well when used on signals altered by a drug, disease model or genetic modification.

Unsupervised mapping of causal relations between brain and behavior
Studies of patients with focal brain lesions provided the historical foundation for cognitive neuroscience, but how to identify a precise mapping between specific brain regions and the cognitive variables affected remains unclear. The challenge lies both in identifying anatomical regions wherein lesions have a shared causal effect, as well as in the precise delineation of the behavioral outcome. Currently, either the relevant brain region or the dimensionality of the behavior being mapped are pre-specified by the investigators rather than both being informed by optimal brain-behavior relationships. Here we apply a novel data-driven causal aggregation algorithm, Causal Feature Learning (CFL) to tackle this challenge in 520 individuals with focal brain lesions. CFL simultaneously constructs macro-level summaries of the spatial distribution of brain lesions and the itemized responses on psychometric tests to optimally characterize the causal brain-behavior relationships. Focusing on the domains of language, visuospatial ability, and depression, we recapitulate established findings, provide new and more precise anatomical results, and present an aggregation of item-wise data that provides an empirical test of extant behavioral scores and can be used to identify novel, psychologically meaningful factors. Future work could use our approach to construct entirely new psychometric variables that might cut across established categories.

Multipair phase-modulated temporal interference electrical stimulation combined with fMRI.
Temporal Interference Stimulation (TI) is a novel brain stimulation technique that aims to integrate the depth characteristic of conventional deep brain stimulation protocols with the non-invasive nature of transcranial electric stimulation. Recent publications in both mice and humans demonstrate that subcortical areas including hippocampus and striatum can be targeted using TI. However, whereas TI stimulation is set to be focused on a specific region of interest, other off-target areas may still be stimulated, including cortical structures. This is a major concern as off-target stimulation carries the risk of modulating unwanted brain structures and circuits. In the present study, we focused on the prefrontal cortex (PFC) in mice and developed a computational modelling approach to identify the best electrode locations for targeting PFC. Using in-vivo electrophysiological recordings and functional magnetic resonance imaging (fMRI) combined with TI, we confirmed the presence of induced TI fields and hemodynamic responses in the PFC but also identified off-target stimulated sites. To minimize the occurrence of off-target effects, we propose a new configuration with three electrode pairs, one of which has an active phase shift of 180 degrees in relation to the other two TI-inducing pairs. The use of this phase-canceling field allowed us to improve the focality of TI by reducing off-target stimulations without significantly affecting the TI field in the target area. The proposed design effectively addresses one of TI's most critical shortcomings and opens new avenues for applications.

Multi-omic analysis of guided and unguided forebrain organoids reveal differences in cellular composition and metabolic profiles
Neural organoids are invaluable model systems for studying neurodevelopment and neurological diseases. For this purpose, reproducible differentiation protocols are needed that minimize inter-organoid variability whilst generating neural organoids that physiologically resemble the brain area of interest. Currently, two main approaches are used: guided, where the differentiation towards neuroectoderm and subsequently specific CNS regions is driven by applying extrinsic signalling molecules, and unguided, where the intrinsic capability of pluripotent stem cells to generate neuroectoderm without external signalling is promoted. Despite the importance for the field, the resulting differences between these models have not been directly investigated. To obtain an unbiased comparison, we performed a multi-omic analysis of forebrain organoids generated using a guided and unguided approach focusing on proteomic, lipidomic and metabolomic differences. Furthermore, we characterised differences in phosphorylation and sialylation states of proteins, two key post-translational modifications (PTMs) in neurodevelopment, and performed single cell transcriptomics (scRNAseq). The multi-omic analysis revealed considerable differences in neuronal-, synaptic and glial content, indicating that guided forebrain organoids contain a larger proportion of neurons, including GABAergic interneurons, and synapses whereas unguided organoids contain significantly more GFAP+ cells and choroid plexus. Furthermore, substantial differences in mitochondrial- and metabolic profiles were identified, pointing to increased levels of oxidative phosphorylation and fatty acid {beta}-oxidation in unguided forebrain organoids and a higher reliance on glycolysis in guided forebrain organoids. Overall, our study comprises a thorough description of the multi-omic differences arising when generating guided and unguided forebrain organoids and provide an important resource for the organoid field studying neurodevelopment and -disease.

Suppression of piriform cortex alters brain-wide dynamics and alleviates seizures in temporal lobe epilepsy
Temporal lobe epilepsy (TLE) is a pathological state that involves altered excitation-inhibition (E-I) in the brain and exhibits recurrent seizures. Many circuit studies of TLE have focused on the hippocampus. Anterior piriform cortex (APC) is also a limbic area closely associated with TLE, but is understudied. In the APC, parvalbumin-expressing (PV+) interneurons provide strong inhibition and help maintain E-I balance. However, whether APCPV neurons play a causal role in TLE is unclear. We used the systemic pilocarpine and intrahippocampal kainic acid (KA) mouse models, which showed pathological changes and spontaneous recurrent seizures (SRSs) akin to those observed in patients with TLE. Whole-cell patch clamp recording and immunohistochemistry were used to examine inhibitory synaptic transmission in the pilocarpine model. Then, using chemogenetics and multi-site local field potential (LFP) recording, we manipulated APCPV neurons at different periods, before applying convulsant, during status epilepticus (SE) and in chronic epileptic phase, and examined the efficacy of APCPV neuronal activation on seizures. For chronic period experiments, KA-injected mice underwent four-site longitudinal LFP recordings. We quantified SRSs based on the frequency and duration of epileptic discharges (> 2 Hz, 10 seconds). For the underlying functional network dynamics, we analyzed the power of each recording site and functional connectivity of each pair of regions in four epileptic states, preictal, ictal, postictal and interictal. In the pilocarpine model, we found impaired synaptic inhibition and loss of PV synapses in the APC. APCPV neuronal pre-activation decreased seizure susceptibility and mortality, but could not stop an ongoing SE. In the chronic KA model, activation of APCPV neurons reduced the frequency and duration of SRSs in the hippocampus. Interestingly, APCPV neuronal activation altered the brain-wide dynamics of seizure network and afforded differential modulation based on epileptic states, brain regions and frequency bands. Our work demonstrates the causal role of APCPV in TLE and provides detailed functional characterization of mechanisms underlying the effectiveness of APCPV activation. We reveal how a cortical microcircuit can alter neural activity in multiple brain regions and exert antiepileptic benefits. These findings strengthen the idea that large-scale connections from APC play a key role in maintaining the E-I balance of the entire seizure network and thus provide the basis for future circuit-based therapies.

Behavioral relevance of category selectivity revealed by human ECoG data
Object recognition is a crucial brain function that involves a complex interplay between various brain regions. However, the behavioral relevance of functional interactions between these regions remains largely unexplored. In this study, we examined the functional interactions between different brain regions during object recognition using intracranial electrocorticography (ECoG) recordings in subjects diagnosed with pharmacologically intractable epilepsy. We computed the phase locking value (PLV) between different brain areas and its category selectivity, and assessed its behavioral relevance by comparing correctly and incorrectly performed trials. Our results revealed that phase locking between brain regions varies across different object categories and that this variability significantly influences the perceptual behavior of subjects. Importantly, we found that the behavioral relevance of these interactions is spatially organized, with long-range (global) connections being more behaviorally relevant for the frontal lobe and local connections being more crucial for the occipital lobe. These findings underscore the unique roles of different brain areas in object recognition and pave the way for more nuanced explorations of the interplay between brain regions in object recognition and other cognitive functions.

Role of spinal sensorimotor circuits in triphasic command: a simulation approach using Goal Exploration Process
During rapid voluntary limb movement about a single joint, a stereotyped triphasic pattern is typically observed in the electromyograms (EMGs) of antagonistic muscles acting at this joint. To explain the origin of such triphasic commands, two types of theories have been proposed. Peripheral theories consider that triphasic commands result from sensorimotor spinal networks, either through a combination of reflexes or through a spinal central pattern generator. Central theories consider that the triphasic command is elaborated in the brain. Although both theories were partially supported by physiological data, there is still no consensus about how exactly triphasic commands are elaborated. Moreover, capacities of simple spinal sensorimotor circuits to elaborate triphasic commands on their own have not been tested yet. In order to test this, we modelled arm musculoskeletal system, muscle activation dynamics, proprioceptive spindle and Golgi afferent activities and spinal sensorimotor circuits. Descending step commands were designed to modify the activity of spinal neurons and the strength of their synapses, either to prepare (SET) the network before movement onset, or to launch the movement (GO). Since these step commands do not contain any dynamics, changes in muscle activities responsible for arm movement rest entirely upon interactions between the spinal network and the musculo-skeletal system. Critically, we selected descending step commands using a Goal Exploration Process inspired from baby babbling during development. In this task, the Goal Exploration Process proved to be very efficient. It proficiently discovered step commands that enabled spinal circuits to handle a broad spectrum of functional behaviors. Notably, this accomplishment was predominantly realized while eliciting natural triphasic commands, thereby substantiating the inherent capacity of the spinal network.

RELEVANCE OF SHAM CONTROL GROUP IN PRECLINICAL ANIMAL STUDIES OF CEREBRAL ISCHEMIA
Background: In experimental animal studies, control sham groups are essential to reduce the influence of the surgical intervention on the analysis. The intraluminal filament procedure is one of the most common models of middle cerebral artery occlusion (MCAO) used in the study of cerebral ischemia. However, in these studies, the sham group has not usually been included in the experimental design because of the assumption that the surgical procedure required to access the middle cerebral artery does not affect brain tissue, or that the results obtained from this group are not relevant. Objectives: In this study, we aimed to evaluate the relevance of the sham group by analyzing and comparing the brain protein profile of a sham and an ischemic group subjected to the surgical intraluminal filament occlusion of the middle cerebral artery. Material and Methods: Three randomized experimental groups were tested: control group (healthy animals), sham group, and ischemic group. Twenty-four hours after the interventional procedure, the brain tissue was evaluated by magnetic resonance imaging (MRI). After animal perfusion, the brain is removed for proteomic analysis by liquid chromatography-mass spectrometry (LC-MS/MS) using both a qualitative analysis by data-dependent acquisition (DDA) mode and a quantitative analysis, using a sequential window acquisition of all theoretical mass spectra (SWATH-MS) method on a hybrid quadrupole time-of-flight mass spectrometer. Results: MRI results showed that only animals subjected to cerebral ischemia had ischemic injury. In the sham group 137 dysregulated proteins were detected compared to the 65 in the ischemic group. Moreover, a comparative study of both protein profiles showed the existence of a pool of 17 that appeared dysregulated in both sham and ischemic animals. These results indicate that the surgical procedure required for intraluminal occlusion of the MCA induce changes on brain protein expression that are not associated with the ischemic lesion. Conclusion: This study highlights the importance of including a sham group in the experimental model design to guarantee that the therapeutic target under study is not affected by the surgical intervention.

Fast inhibition slows and desynchronizes auditory efferent neuron activity
The encoding of acoustic stimuli requires precise neuron timing. Auditory neurons in the cochlear nucleus (CN) and brainstem are well-suited for accurate analysis of fast acoustic signals, given their physiological specializations of fast membrane time constants, fast axonal conduction, and reliable synaptic transmission. The medial olivocochlear (MOC) neurons that provide efferent inhibition of the cochlea reside in the ventral brainstem and participate in these fast neural circuits. However, their modulation of cochlear function occurs over time scales of a slower nature. This suggests the presence of mechanisms that restrict MOC inhibition of cochlear function. To determine how monaural excitatory and inhibitory synaptic inputs integrate to affect the timing of MOC neuron activity, we developed a novel in vitro slice preparation (wedge-slice). The wedge-slice maintains the ascending auditory nerve root, the entire CN and projecting axons, while preserving the ability to perform visually guided patch-clamp electrophysiology recordings from genetically identified MOC neurons. The in vivo-like timing of the wedge-slice demonstrates that the inhibitory pathway accelerates relative to the excitatory pathway when the ascending circuit is intact, and the CN portion of the inhibitory circuit is precise enough to compensate for reduced precision in later synapses. When combined with machine learning PSC analysis and computational modeling, we demonstrate a larger suppression of MOC neuron activity when the inhibition occurs with in vivo-like timing. This delay of MOC activity may ensure that the MOC system is only engaged by sustained background sounds, preventing a maladaptive hyper-suppression of cochlear activity.

The Neuroprotective Effect of Short-chain Fatty Acids Against Hypoxia-reperfusion Injury
Gut microbe-derived short-chain fatty acids (SCFAs) are known to have a profound impact on various brain functions, including cognition, mood, and overall neurological health. However, their role, if any, in protecting against hypoxic injury and ischemic stroke has not been extensively studied. In this study, we investigated the effects of two major SCFAs abundant in the gut, propionate (P) and butyrate (B), on hypoxia-reperfusion injury using a neuronal cell line and a zebrafish model. Neuro 2a (N2a) cells treated with P and B exhibited reduced levels of mitochondrial and cytosolic reactive oxygen species (ROS), diminished loss of mitochondrial membrane potential, suppressed caspase activation, and lower rates of cell death when exposed to CoCl2-induced hypoxia, compared to the control group. Furthermore, adult zebrafish fed with SCFAs-supplemented feeds showed less susceptibility to hypoxic conditions compared to the control group, as indicated by multiple behavioral measures. Histological analysis of TTC-stained brain sections revealed lesser damage in the SCFAs-fed group. We also found that FABP7 (also known as BLBP), a neuroprotective fatty acid binding protein, was upregulated in the brains of the SCFAs-fed group. Additionally, when FABP7 was overexpressed in N2a cells, it protected the cells from hypoxia-reperfusion injury. Overall, our data clearly demonstrates a neuroprotective role of P and B against hypoxic brain injury and suggests the potential of dietary supplementation with SCFAs to mitigate stroke-induced brain damage.

Distinct transcriptional programs define a heterogeneous neuronal ensemble for social interaction
Reliable representations of information regarding complex behaviors including social interactions require the coordinated activity of heterogeneous cell types within distributed brain regions. Activity in the medial prefrontal cortex is critical in regulating social behavior, but our understanding of the specific cell types which comprise the social ensemble has been limited by available mouse lines and molecular tagging strategies which rely on the expression of a single marker gene. Here we sought to quantify the heterogeneous neuronal populations which are recruited during social interaction in parallel in a non-biased manner and determine how distinct cell types are differentially active during social interactions. We identify distinct populations of prefrontal neurons activated by social interaction by quantification of immediate early gene (IEG) expression in transcriptomically clustered neurons. This approach revealed variability in the recruitment of different excitatory and inhibitory populations within the medial prefrontal cortex. Furthermore, evaluation of the populations of IEGs recruited following social interaction revealed both cell-type and region-specific transcriptional programs, suggesting that reliance on a single molecular marker is insufficient to quantify activation across all cell types. Our findings provide a comprehensive description of cell-type specific transcriptional programs invoked by social interactions and reveal new insights into the heterogeneous neuronal populations which compose the social ensemble.

Bidirectional relationship between attentional deficits and escalation of nicotine intake
Smoking addicts have deficits in cognition, in particular deficits in attention, even long after smoking cessation. It is not clear however, whether deficits are a cause or a consequence, or both, of chronic nicotine use. Here we set out a series of experiments in rats to address this question and, more specifically, to assess the long-term effects of exposure to and withdrawal from chronic nicotine self-administration on attentional performance. Animals were trained in a 5-choice serial reaction time task to probe individual attentional performance and, then, were given access to a fixed versus increasing dose of intravenous nicotine for self-administration, a differential dose procedure known to induce two between-session patterns of nicotine intake: a stable versus escalation pattern. Attentional performance was measured daily before, during and also 24-h after chronic access to the differential dose procedure of nicotine self-administration. We found that pre-existing individual variation in attentional performance predicts individual vulnerability to develop escalation of nicotine intake. Moreover, while chronic nicotine self-administration increases attention, withdrawal from nicotine intake escalation induces attentional deficits, a withdrawal effect that is dose-dependently reversed by acute nicotine. Together, these results suggest that pre-existing individual variation in attentional performance predicts individual vulnerability to develop escalation of nicotine intake, and that part of the motivation for using nicotine during escalation might be to alleviate withdrawal-induced attentional deficits.

Discerning state estimation and sensory gating, two presumptive predictive signals in mouse barrel cortex
The brain is assumed to contain distinctive predictive systems ranging from sensorimotor to cognitive functions. Here we report the successful functional delineation of two different presumptive predictive systems on the neuronal level, state estimation (SE) and sensory gating (SG), which both attenuate sensory flow during movement. Studying neuronal sensorimotor responses throughout the depth of primary somatosensory cortex in mice trained on a whisker reach task, SE appeared as a learned attenuation of tactile signal flow, due to a suppressive predictive signal, precisely at the time of an experimental sensory consequence. In contrast, SG was observable during a much longer interval after onset of the motor command. Both phenomena are internal, presumptively predictive signals, as blockade of the reafference did not affect them. We speculate that SG may be related to cognitive signals monitoring goals of movements, while SE likely is the expression of the classical notion of the reafference principle.

Nitric oxide mediates differential effects in mouse retinal ganglion cells
Neuromodulators have major influences on the regulation of neural circuit activity across the nervous system. Nitric oxide (NO) is a prominent neuromodulator in many circuits, and has been extensively studied in the retina across species. NO has been associated with the regulation of light adaptation, gain control, and gap junction coupling, but its effect on the retinal output, specifically on the different types of retinal ganglion cells (RGCs), is still poorly understood. Here, we used two-photon Ca2+ imaging to record RGC responses to visual stimuli to investigate the neuromodulatory effects of NO on the cell type-level in the ex vivo mouse retina. We found that about one third of the RGC types displayed highly reproducible and cell type-specific response changes during the course of an experiment, even in the absence of NO. Accounting for these adaptational changes allowed us to isolate NO effects on RGC responses. This revealed that NO affected only a few RGC types, which typically became more active due to a reduction of their response suppression. Notably, NO had no discernible effect on their spatial receptive field size and surround strength. Together, our data suggest that NO specifically modulates suppression of the temporal response in a distinct group of contrast-suppressed RGC types. Finally, our study demonstrates the need for recording paradigms that takes adaptational, non-drug-related response changes into account when analysing potentially subtle pharmacological effects.

Perceptual Foundation and Extension to Phase Tagging for Rapid Invisible Frequency Tagging (RIFT)
Recent years have seen the emergence of a visual stimulation protocol called Rapid Invisible Frequency Tagging (RIFT) in cognitive neuroscience. In RIFT experiments, visual stimuli are presented at a rapidly and sinusoidally oscillating luminance, using high refresh rate projection equipment. Such stimuli result in strong steady-state responses in visual cortex, measurable extracranially using EEG or MEG. The high signal-to-noise ratio of these neural signals, combined with the alleged invisibility of the manipulation, make RIFT a potentially promising technique to study the neural basis of visual processing. In this study, we set out to resolve two fundamental, yet still outstanding, issues regarding RIFT; as well as to open up a new avenue for taking RIFT beyond frequency tagging per se. First, we provide robust evidence that RIFT is indeed subjectively undetectable, going beyond previous anecdotal reports. Second, we demonstrate that full-amplitude luminance or contrast manipulation offer the best tagging results. Third and finally, we demonstrate that, in addition to frequency tagging, phase tagging can reliably be used in RIFT studies, opening up new avenues for constructing RIFT experiments. Together, this provides a solid foundation for using RIFT in visual cognitive neuroscience.

News without the buzz: reading out weak theta rhythms in the hippocampus
Local field potentials (LFPs) reflect the collective dynamics of neural populations, yet their exact relationship to neural codes remains unknown. One notable exception is the theta rhythm of the rodent hippocampus, which seems to provide a reference clock to decode the animal's position from spatiotemporal patterns of neuronal spiking or LFPs. But when the animal stops, theta becomes irregular, potentially indicating the breakdown of temporal coding by neural populations. Here we show that no such breakdown occurs, introducing an artificial neural network that can recover position-tuned rhythmic patterns (pThetas) without relying on the more prominent theta rhythm as a reference clock. pTheta and theta preferentially correlate with place cell and interneuron spiking, respectively. When rats forage in an open field, pTheta is jointly tuned to position and head orientation, a property not seen in individual place cells but expected to emerge from place cell sequences. Our work demonstrates that weak and intermittent oscillations, as seen in many brain regions and species, can carry behavioral information commensurate with population spike codes.

Egg-laying hormone expression in identified neurons across developmental stages and reproductive states of the nudibranch Berghia stephanieae
Neuropeptides play essential roles in coordinating reproduction. Egg-laying hormone (ELH) is conserved in genetic sequence and behavioral function across molluscs, where neuronal clusters secrete ELH to modulate and induce egg-laying. Here we investigated ELH in the nudibranch mollusc, Berghia stephanieae. ELH preprohormone gene orthologs, which showed clade-specific differences at the C-terminus of the predicted bioactive peptide, were identified in brain transcriptomes across several nudipleuran species, including B. stephanieae. Injection of synthesized B. stephanieae ELH peptide into mature individuals induced egg-laying. ELH gene expression in the brain and body was mapped using in-situ hybridization chain reaction. Across the adult brain, 300-400 neurons expressed ELH. Twenty-one different cell types were identified in adults, three of which were located unilaterally on the right side, which corresponds to the location of the reproductive organs. Ten cell types were present in pre-reproductive juvenile stages. An asymmetric cluster of approximately 100 small neurons appeared in the right pedal ganglion of late-stage juveniles. Additional neurons in the pleural and pedal ganglia expressed ELH only in adults that were actively laying eggs and sub-adults that were on the verge of doing so, implicating their direct role in reproduction. Outside the brain, ELH was expressed on sensory appendages, including in presumptive sensory neurons. ELH shares deep homology with the corticotropin-releasing hormone gene family, which has roles broadly in stress response. Its widespread expression in the nudibranch B. stephanieae suggests that ELH plays a role beyond reproduction in gastropod molluscs.

Diroximel fumarate acts through Nrf2 to attenuate methylglyoxal-induced nociception in mice and decreases ISR activation in DRG neurons
Diabetic neuropathic pain is associated with elevated plasma levels of methylglyoxal (MGO). MGO is a metabolite of glycolysis that causes mechanical hypersensitivity in mice by inducing the integrated stress response (ISR), which is characterized by phosphorylation of eukaryotic initiation factor 2 (p-eIF2). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates the expression of antioxidant proteins that neutralize MGO. We hypothesized that activating Nrf2 using diroximel fumarate (DRF) would alleviate MGO-induced pain hypersensitivity. We pretreated male and female C57BL/6 mice daily with oral DRF prior to intraplantar injection of MGO (20 ng). DRF (100 mg/kg) treated animals were protected from developing MGO-induced mechanical and cold hypersensitivity. Using Nrf2 knockout mice we demonstrate that Nrf2 is necessary for the anti-nociceptive effects of DRF. In cultured mouse and human dorsal root ganglion (DRG) sensory neurons, we found that MGO induced elevated levels of p-eIF2. Co-treatment of MGO (1 M) with monomethyl fumarate (MMF, 10, 20, 50 M), the active metabolite of DRF, reduced p-eIF2 levels and prevented aberrant neurite outgrowth in human DRG neurons. Our data show that targeting the Nrf2 antioxidant system with DRF is a strategy to potentially alleviate pain associated with elevated MGO levels.

An exploratory computational analysis in mice brain networks of widespread epileptic seizure onset locations along with potential strategies for effective intervention and propagation control
Mean-field models have been developed to replicate key features of epileptic seizure dynamics. However, the precise mechanisms and the role of the brain area responsible for seizure onset and propagation remain incompletely understood. In this study, we employ computational methods within The Virtual Brain framework and the Epileptor model to explore how the location and connectivity of an Epileptogenic Zone (EZ) in a mouse brain are related to focal seizures (seizures that start in one brain area and may or may not remain localized), with a specific focus on the hippocampal region known for its association with epileptic seizures. We then devise computational strategies to confine seizures (prevent widespread propagation), simulating medical-like treatments such as tissue resection and the application of an anti-seizure drugs or neurostimulation to suppress hyperexcitability. Through selectively removing (blocking) specific connections informed by the structural connectome and graph network measurements or by locally reducing outgoing connection weights of EZ areas, we demonstrate that seizures can be kept constrained around the EZ region. We successfully identified the minimal connections necessary to prevent widespread seizures, with a particular focus on minimizing surgical or medical intervention while simultaneously preserving the original structural connectivity and maximizing brain functionality.

Angiotensin-II drives changes in microglia-vascular interactions in rats with heart failure
Activation of microglia, the resident immune cells of the central nervous system, leading to the subsequent release of pro-inflammatory cytokines, has been linked to cardiac remodeling, autonomic disbalance, and cognitive deficits in heart failure (HF). While previous studies emphasized the role of hippocampal Angiotensin II (AngII) signaling in HF-induced microglial activation, unanswered mechanistic questions persist. Evidence suggests significant interactions between microglia and local microvasculature, potentially affecting blood-brain barrier integrity and cerebral blood flow regulation. Still, whether the microglial-vascular interface is affected in the brain during HF remains unknow. Using a well-established ischemic HF rat model, we demonstrate increased vessel-associated microglia (VAM) in HF rat hippocampi, which showed heightened expression of AngII AT1a receptors. Acute AngII administration to sham rats induced microglia recruitment to the perivascular space, along with increased expression of TNFa. Conversely, administering an AT1aR blocker to HF rats prevented the recruitment of microglia to the perivascular space, normalizing their levels to those in healthy rats. These results highlight the critical importance of a rather understudied phenomenon (i.e., microglia-vascular interactions in the brain) in the context of the pathophysiology of a highly prevalent cardiovascular disease, and unveil novel potential therapeutic avenues aimed at mitigating neuroinflammation in cardiovascular diseases.

Decoding Pain: Uncovering the Factors that Affect Performance of Neuroimaging-Based Pain Models
Neuroimaging-based pain biomarkers, when combined with machine learning techniques, have demonstrated potential in decoding pain intensity and diagnosing clinical pain conditions. However, a systematic evaluation of how different modeling options affect model performance remains unexplored. This study presents results from a comprehensive literature survey and benchmarking analysis. We conducted a survey of 57 previously published articles that included neuroimaging-based predictive modeling of pain, comparing classification and prediction performance based on the following modeling variables-the levels of data, spatial scales, idiographic vs. population models, and sample sizes. The findings revealed a preference for population-level modeling with brain-wide features, aligning with the goal of clinical translation of neuroimaging biomarkers. However, a systematic evaluation of the influence of different modeling options was hindered by a limited number of independent test results. This prompted us to conduct benchmarking analyses using a locally collected functional Magnetic Resonance Imaging (fMRI) dataset (N = 124) involving an experimental thermal pain task. The results clearly demonstrated that data levels, spatial scales, and sample sizes significantly impact model performance. Specifically, incorporating more pain-related brain regions, increasing sample sizes, and using less data averaging in training while increasing it in testing enhanced performance. These findings provide a useful reference for decision-making in the development of neuroimaging-based biomarkers, highlighting the importance of the careful selection of modeling strategies and options to build better-performing neuroimaging pain biomarkers. These findings offer useful guidance for developing neuroimaging-based biomarkers, underscoring the importance of strategic selection of modeling approaches to build better-performing neuroimaging pain biomarkers.

The human pupil and face encode sound affect and provide objective signatures of tinnitus and auditory hypersensitivity disorders
Central disinhibition works like an amplifier, boosting neural sensitivity to progressively weaker peripheral inputs arising from degenerating sensory organs. The Excess Central Gain model posits that central disinhibition also gives rise to cardinal features of sensory disorders including sensory overload and phantom percepts. Here, we tested predictions of this model with neural, autonomic, and behavioral approaches in participants with sound sensitivity and tinnitus (phantom ringing). We confirmed enhanced auditory neural gain but found no association with their sound aversion and anxiety. Instead, we hypothesized that symptom severity was linked to affective sound encoding. In neurotypical controls, emotionally evocative sounds elicited pupil dilations, electrodermal responses and facial reactions that scaled with valence. Participants with disordered hearing exhibited disrupted pupil and facial reactivity that accurately predicted their self-reported tinnitus and hyperacusis severity. These findings highlight auditory-limbic dysregulation in tinnitus and sound sensitivity disorders and introduce approaches for their objective measurement.

Intensive task-switching training and single-task training differentially affect behavioral and neural manifestations of cognitive control in children
The ability to flexibly switch between tasks develops during childhood. Children's task-switching performance improves with practice, but the underlying processes remain unclear. We examined how nine weeks of task-switching training affect performance and task-related activation and connectivity as assessed by functional magnetic resonance imaging. Children (8-11 years) were pseudo-randomly assigned to three groups: high-intensity task switching (SW; n = 70), high-intensity single tasking (SI; n = 72), and passive control (n = 41). After three weeks, drift-diffusion modeling revealed faster evidence accumulation and more cautious responding in both training groups relative to the control group. At the end of training, these changes were maintained in the SW group only, that also showed activation decreases in dorsolateral prefrontal cortex. Functional connectivity increases associated with task-switching demands became less pronounced with practice in both training groups, with more persistent decreases in the SI group. We conclude that task-switching training altered performance by accelerating evidence accumulation and promoting more cautious responding. Faster evidence accumulation along with decreased task-related activations suggest increased processing efficiency in frontoparietal regions with training. More intense task-switching training helped maintain these changes, possibly by facilitating plastic change through the protracted mismatch between processing supplies and environmental demands.

Human cerebrospinal fluid single exosomes in Parkinson and Alzheimer diseases
Exosomes are proposed to be important in the pathogenesis of prevalent neurodegenerative diseases. We report the first application of solid-state technology to perform multiplex analysis of single exosomes in human cerebrospinal fluid (CSF) obtained from the lumbar sac of people diagnosed with Alzheimer disease dementia (ADD, n=30) or Parkinson disease dementia (PDD, n=30), as well as age-matched healthy controls (HCN, n=30). Single events were captured with mouse monoclonal antibodies to one of three different tetraspanins (CD9, CD63, or CD81) or with mouse (M) IgG control, and then probed with fluorescently labeled antibodies to prion protein (PrP) or CD47 to mark neuronal or presynaptic origin, as well as ADD- and PDD-related proteins: amyloid beta (A{beta}), tau, -synuclein, and Apolipoprotein (Apo) E. Data were collected only from captured events that were within the size range of 50 to 200 nm. Exosomes were present at approximately 100 billion per mL human CSF and were similarly abundant for CD9+ and CD81+ events, but CD63+ were only 22% to 25% of CD9+ (P<0.0001) or CD81+ (P<0.0001) events. Approximately 24% of CSF exosomes were PrP+, while only 2% were CD47+. The vast majority of exosomes were surface ApoE+, and the number of PrP-ApoE+ (P<0.001) and PrP+ApoE+ (P<0.01) exosomes were significantly reduced in ADD vs. HCN for CD9+ events only. A{beta}, tau, and -synuclein were not detected on the exosome surface or in permeabilized cargo. These data provide new insights into single exosome molecular features and highlight reduction in the CSF concentration of ApoE+ exosomes in patients with ADD.

CompHEAR: A Customizable and Scalable Web-Enabled Auditory Performance Evaluation Platform for Cochlear Implant Sound Processing Research
Objective: Cochlear implants (CIs) are auditory prostheses for individuals with severe to profound hearing loss, offering substantial but incomplete restoration of hearing function by stimulating the auditory nerve using electrodes. However, progress in CI performance and innovation has been constrained by the inability to rapidly test multiple sound processing strategies. Current research interfaces provided by major CI manufacturers have limitations in supporting a wide range of auditory experiments due to portability, programming difficulties, and the lack of direct comparison between sound processing algorithms. To address these limitations, we present the CompHEAR research platform, designed specifically for the Cochlear Implant Hackathon, enabling researchers to conduct diverse auditory experiments on a large scale. Study Design: Quasi-experimental. Setting: Virtual. Methods: CompHEAR is an open-source, user-friendly platform which offers flexibility and ease of customization, allowing researchers to set up a broad set of auditory experiments. CompHEAR employs a vocoder to simulate novel sound coding strategies for CIs. It facilitates even distribution of listening tasks among participants and delivers real-time metrics for evaluation. The software architecture underlies the platform's flexibility in experimental design and its wide range of applications in sound processing research. Results: Performance testing of the CompHEAR platform ensured that it could support at least 10,000 concurrent users. The CompHEAR platform was successfully implemented during the COVID-19 pandemic and enabled global collaboration for the CI Hackathon (www.cihackathon.com). Conclusion: The CompHEAR platform is a useful research tool that permits comparing diverse signal processing strategies across a variety of auditory tasks with crowdsourced judging. Its versatility, scalability, and ease of use can enable further research with the goal of promoting advancements in cochlear implant performance and improved patient outcomes.

Large scale, simultaneous chronic neural recordings from multiple brain areas
Understanding how brain activity is related to animal behavior requires measuring multi-area interactions on multiple timescales. However, methods to perform chronic, simultaneous recordings of neural activity from many brain areas are lacking. Here, we introduce a novel approach for independent chronic probe implantation that enables flexible, simultaneous interrogation of neural activity from many brain regions during head restrained or freely moving behavior. The approach enables repeated retrieval and reimplantation of probes. The chronic implantation approach can be combined with other modalities such as skull clearing for cortex wide access and optogenetics with optic fibers. Using this approach, we implanted 6 probes chronically in one hemisphere of the mouse brain. The implant is lightweight, allows flexible targeting with different angles, and offers enhanced stability. Our approach broadens the applications of chronic recording while retaining its main advantages over acute recording (superior stability, longitudinal monitoring of activity and freely moving interrogations) and provides an appealing avenue to study processes not accessible by acute methods, such as the neural substrate of learning across multiple areas.

Reliability of task-based fMRI in the dorsal horn of the human spinal cord
The application of functional magnetic resonance imaging (fMRI) to the human spinal cord is still a relatively small field of research and faces many challenges. Here we aimed to probe the limitations of task-based spinal fMRI at 3T by investigating the reliability of spinal cord blood oxygen level dependent (BOLD) responses to repeated nociceptive stimulation across two consecutive days in 40 healthy volunteers. We assessed the test-retest reliability of subjective ratings, autonomic responses, and spinal cord BOLD responses to short heat pain stimuli (1s duration) using the intraclass correlation coefficient (ICC). At the group level, we observed robust autonomic responses as well as spatially specific spinal cord BOLD responses at the expected location, but no spatial overlap in BOLD response patterns across days. While autonomic indicators of pain processing showed good-to-excellent reliability, both {beta}-estimates and z-scores of task-related BOLD responses showed poor reliability across days in the target region (gray matter of the ipsilateral dorsal horn). When taking into account the sensitivity of gradient-echo echo planar imaging (GE-EPI) to draining vein signals by including the venous plexus in the analysis, we observed BOLD responses with good reliability across days. Taken together, these results demonstrate that heat pain stimuli as short as one second are able to evoke a robust and spatially specific BOLD response, which is however strongly variable within participants across time, resulting in low reliability in the dorsal horn gray matter. Further improvements in data acquisition and analysis techniques are thus necessary before event-related spinal cord fMRI as used here can be reliably employed in longitudinal designs or clinical settings.

Multilayer Network Analysis across Cortical Depths in Resting-State 7T fMRI
In graph theory, "multilayer networks" represent systems involving several interconnected topological levels. A neuroscience example is the hierarchy of connections between different cortical depths or "lamina". This hierarchy is becoming non-invasively accessible in humans using ultra-high-resolution functional MRI (fMRI). Here, we applied multilayer graph theory to examine functional connectivity across different cortical depths in humans, using 7T fMRI (1-mm3 voxels; 30 participants). Blood oxygenation level dependent (BOLD) signals were derived from five depths between the white matter and pial surface. We then compared networks where the inter-regional connections were limited to a single cortical depth only ("layer-by-layer matrices") to those considering all possible connections between regions and cortical depths ("multilayer matrix"). We utilized global and local graph theory features that quantitatively characterize network attributes such as network composition, nodal centrality, path-based measures, and hub segregation. Detecting functional differences between cortical depths was improved using multilayer connectomics compared to the layer-by-layer versions. Superficial aspects of the cortex dominated information transfer and deeper aspects clustering. These differences were largest in frontotemporal and limbic brain regions. fMRI functional connectivity across different cortical depths may contain neurophysiologically relevant information. Multilayer connectomics could provide a methodological framework for studies on how information flows across this hierarchy.

Single-nucleus multiomic atlas of frontal cortex in amyotrophic lateral sclerosis with a deep learning-based decoding of alternative polyadenylation mechanisms
The understanding of how different cell types contribute to amyotrophic lateral sclerosis (ALS) pathogenesis is limited. Here we generated a single-nucleus transcriptomic and epigenomic atlas of the frontal cortex of ALS cases with C9orf72 (C9) hexanucleotide repeat expansions and sporadic ALS (sALS). Our findings reveal shared pathways in C9-ALS and sALS, characterized by synaptic dysfunction in excitatory neurons and a disease-associated state in microglia. The disease subtypes diverge with loss of astrocyte homeostasis in C9-ALS, and a more substantial disturbance of inhibitory neurons in sALS. Leveraging high depth 3'-end sequencing, we found a widespread switch towards distal polyadenylation (PA) site usage across ALS subtypes relative to controls. To explore this differential alternative PA (APA), we developed APA-Net, a deep neural network model that uses transcript sequence and expression levels of RNA-binding proteins (RBPs) to predict cell-type specific APA usage and RBP interactions likely to regulate APA across disease subtypes.

Precise 3D Localization of Intracerebral Implants with a simple Brain Clearing Method
Accurately determining the localization of intracerebral implants stands as a critical final step in numerous in-vivo studies, especially when targeting deep, small nuclei. Conventional histological approaches, reliant on manual estimation through sectioning and slice examination, often introduce errors and damage, potentially complicating data interpretation. Leveraging recent advancements in tissue-clearing techniques and light-sheet fluorescence microscopy, we introduce a method enabling virtual brain slicing in any orientation, offering precise implant localization without the limitations of traditional sectioning. To illustrate this method's efficacy, we present findings from the acute implantation of linear silicon probes in the midbrain interpeduncular nucleus (IPN) of anesthetized transgenic mice expressing chanelrhodopsin-2 EYFP under the choline acetyltransferase ChAT promoter/enhancer regions (ChAT-Chr2-EYFP mice). Utilizing a fluorescent dye applied to the electrode's surface, we visualize both the targeted area and electrode position. Brain scans, presented effortlessly in video format across various orientations, showcase the technique's versatility. Additionally, automated registration accurately pinpoints implant localization, enabling enhanced inter-subject comparisons.

The LH receptor regulates hippocampal spatial memory and restores dendritic spine density in ovariectomized APP/PS1 AD mice
Activation of the luteinizing hormone receptor (LHCGR) rescues spatial memory function and spine density losses associated with gonadectomy and high circulating gonadotropin levels in females. However, whether this extends to the AD brain or the mechanisms that underlie these benefits remain unknown. To address this question, we delivered the LHCGR agonist human chorionic gonadotropin (hCG) intracerebroventricularly (ICV), under reproductively intact and ovariectomized conditions to mimic the post-menopausal state in the APP/PS1 mouse brain. Cognitive function was tested using the Morris water maze task, and hippocampal dendritic spine density, Abeta; pathology, and signaling changes associated with these endpoints were determined to address mechanisms. Here we show that central LHCGR activation restored function in ovariectomized APP/PS1 female mice to wild-type levels without altering Abeta; pathology. LHCGR activation increased hippocampal dendritic spine density regardless of reproductive status, and this was mediated by BDNF-dependent and independent signaling. We also show that ovariectomy in the APP/PS1 brain elicits an increase in peripherally derived pro-inflammatory genes which are inhibited by LHCGR activation. This may mediate reproductive status specific effects of LHCGR agonism on cognitive function and BDNF expression. Together, this work highlights the relevance of the LHCGR on cognition and its therapeutic potential in the menopausal AD brain.

Functional mapping of the somatosensory cortex using noninvasive fMRI and touch in awake dogs
Dogs are increasingly used as a model for neuroscience due to their ability to undergo functional MRI fully awake and unrestrained, after extensive behavioral training. Still, we know rather little about dogs' basic functional neuroanatomy, including how basic perceptual and motor functions are localized in their brains. This is a major shortcoming in interpreting activations obtained in dog fMRI. The aim of this preregistered study was to localize areas associated with somatosensory processing. To this end, we touched N = 22 dogs undergoing fMRI scanning on their left and right flanks using a wooden rod. We identified activation in anatomically defined primary and secondary somatosensory areas (SI and SII), lateralized to the contralateral hemisphere depending on the side of touch, as well as activations, beyond an anatomical mask of SI and SII, in the cingulate cortex, right cerebellum and vermis, and the Sylvian gyri. These activations may partly relate to motor control (cerebellum, cingulate), but also potentially to higher-order cognitive processing of somatosensory stimuli (rostral Sylvian gyri), and the affective aspects of the stimulation (cingulate). We also found evidence for individual side biases in a vast majority of dogs in our sample, pointing at functional lateralization of somatosensory processing. These findings not only provide further evidence that fMRI is suited to localize neuro-cognitive processing in dogs in vivo, but also expand our understanding of touch processing in mammals, beyond classically defined primary and secondary somatosensory cortices.

Netrin4 is a new target specific factor, ensuring adult sympathetic neuron survival via promoting protein synthesis
How mature neurons survive under homeostasis is a question of utmost importance and is known to be different from developing neurons. However, the understanding of this regard remains largely unknown. Here, based on the relationship between the sympathetic cervical ganglia (SCG) and the arterial networks of projecting and targeting organs, we report that the secretome of cerebral, but not peripheral, arterial smooth muscles (SMC) was required for the survival of sympathetic neurons. Among the secretome, we further identified that netrin-4, encoded by the ntn-4 gene, only entered neurons and not glia and played a crucial role both in vitro and in vivo. This was demonstrated with three independent lines of tamoxifen-inducible SMC-specific conditional knockout mice (cKO). Notably, in cKO mice, the local supply of exogenous netrin-4 confined to SCG selectively rescued neuronal necroptosis, which otherwise consistently occurred in a specific subgroup of SCG neurons that innervate cerebral SMCs. Mechanistically, we demonstrated that cerebral netrin-4 was endocytosed at the neurovascular interface and retrogradely long transported to peripheral soma in SCG, where it differentially regulated mRNA translations. This regulation suppressed vacuolization and neuronal necrosis, both of which took place spontaneously in cKO mice. The former is immediately followed by the latter when we injured axons using two-photon laser ablation. The findings revealed a new principle of neurovascular interactions vital for mature neuron survival, implying that under circumstances of cerebral SMC insufficient secretion, such as natural aging, may initiate mature neuronal loss due to uncontrolled vacuolization.

Neural adaptation at stimulus onset and speed of neural processing as critical contributors to speech comprehension independent of hearing threshold or age
Loss of afferent auditory fiber function (cochlear synaptopathy) has been suggested to occur before a clinically measurable deterioration of subjective hearing threshold. This so-called "hidden" hearing loss is characterized by speech comprehension difficulties. We examined young, middle-aged, and older individuals with and without hearing loss using pure-tone (PT) audiometry, short-pulsed distortion-product otoacoustic emissions (DPOAE), auditory brainstem responses (ABR), auditory steady state responses (ASSR), speech comprehension (OLSA), and syllable discrimination in quiet and noise. After normalizing OLSA thresholds for PT thresholds ("PNOT"), differences in speech comprehension still remained and showed no significant dependence on age, allowing us to categorize participants into groups with good, standard, and poor speech comprehension. Listeners with poor speech comprehension in quiet exhibited smaller firing rate adaptions at stimulus onset (as measured by the difference between DPOAE threshold and pure-tone threshold) and delayed supra-threshold ABR waves I-V, suggesting high spontaneous rate low threshold fiber cochlear synaptopathy. In contrast, when speech comprehension was tested in noise, listeners with poor speech comprehension had larger DPOAEs acceptance rate, putatively resulting from altered basilar membrane compression (recruitment). This was linked with higher uncomfortable loudness levels and larger ASSR amplitudes. Moreover, performance in phoneme discrimination was significantly different below (/o/-/u/) and above the phase-locking limit (/i/-/y/), depending on whether vowels were presented in quiet or ipsilateral noise. This suggests that neural firing rate adaptation at stimulus onset is critical for speech comprehension, independent of hearing threshold and age, whereas the recruitment phenomenon counterbalances the loss in speech-in-noise discrimination due to impaired threshold.

Diet-induced miRNAs regulate adult neurogenesis and functional activity of nascent neurons in the hypothalamus
Neurogenesis in the hypothalamus upon high fat diet (HFD) feeding regulates the feeding circuit. HFD induces the neurogenesis of {beta}2 tanycytes in young- adult mice. However molecular mechanisms of tanycytic neurogenesis; and their functional integration into the feeding circuitry are poorly understood. We investigated the role of miRNAs in the regulation of HFD-induced tanycytic neurogenesis. miRNA arrays identified a cohort of HFD-induced, differentially-regulated miRNAs in BrdU+ {beta}2-tanycytes. These miRNAs arise from different chromosomes, rather than a single cluster. In silico network analysis on the predicted targets of all five HFD-induced miRNAs and reporter assays identified a subset of targets that influence neurogenesis and neuronal differentiation. HFD-induced miRNAs drive a molecular program leading to the functional integration of nascent neurons; introduction of a miRNA sponge sequestering all five miRNAs abolishes it. Diet-regulated newborn neurons preferentially differentiate into AgRP+ neurons that functionally integrate into the feeding circuit.

Pseudo-craniotomy of a whole-brain model reveals tumor-induced alterations to neuronal dynamics in glioma patients
Brain tumors can induce pathological changes in neuronal dynamics both on a local and global level. Here, we use a whole-brain modeling approach to investigate these pathological alterations in neuronal activity. By fitting a Hopf whole-brain model to empirical functional connectivity, we demonstrate that phase correlations are largely determined by the ratio of interregional coupling strength and intraregional excitability. Furthermore, we observe considerable differences in interregional-versus-intraregional dynamics between glioma patients and healthy controls, both on an individual and population-based level. In particular, we show that local tumor pathology induces shifts in the global brain dynamics by promoting the contribution of interregional interactions. Our approach demonstrates that whole-brain models provide valuable insights for understanding glioma-associated alterations in functional connectivity.

The Brain Image Library: A Community-Contributed Microscopy Resource for Neuroscientists
Advancements in microscopy techniques and computing technologies have enabled researchers to digitally reconstruct brains at micron scale. As a result, community efforts like the BRAIN Initiative Cell Census Network (BICCN) have generated thousands of whole-brain imaging datasets to trace neuronal circuitry and comprehensively map cell types. This data holds valuable information that extends beyond initial analyses, opening avenues for variation studies and robust classification of cell types in specific brain regions. However, the size and heterogeneity of these imaging data have historically made storage, sharing, and analysis difficult for individual investigators and impractical on a broad community scale. Here, we introduce the Brain Image Library (BIL), a public resource serving the neuroscience community that provides a persistent centralized repository for brain microscopy data. BIL currently holds thousands of brain datasets and provides an integrated analysis ecosystem, allowing for exploration, visualization, and data access without the need to download, thus encouraging scientific discovery and data reuse.

Trans-synaptic molecular context of NMDA receptor nanodomains
Tight coordination of the spatial relationships between protein complexes is required for cellular function. In neuronal synapses, many proteins responsible for neurotransmission organize into subsynaptic nanoclusters whose trans-cellular alignment modulates synaptic signal propagation. However, the spatial relationships between these proteins and NMDA receptors (NMDARs), which are required for learning and memory, remain undefined. Here, we mapped the relationship of key NMDAR subunits to reference proteins in the active zone and postsynaptic density using multiplexed super-resolution DNA-PAINT microscopy. GluN2A and GluN2B subunits formed nanoclusters with diverse configurations that, surprisingly, were not localized near presynaptic vesicle release sites marked by Munc13-1. However, a subset of presynaptic sites was configured to maintain NMDAR activation: these were internally denser, aligned with abundant PSD-95, and associated closely with specific NMDAR nanodomains. This work reveals a new principle regulating NMDAR signaling and suggests that synaptic functional architecture depends on assembly of multiprotein nanodomains whose interior construction is conditional on trans-cellular relationships.

Combining transcutaneous spinal stimulation and functional electrical stimulation increases force generated by lower limbs: When more is more
BackgroundTranscutaneous Spinal Stimulation (TSS) has been shown to promote activation of the lower limb and trunk muscles and is being actively explored for improving the motor outcomes of people with neurological conditions. However, individual responses to TSS vary, and often the muscle responses are insufficient to produce enough force for self-supported standing. Functional electrical stimulation (FES) can activate individual muscles and assist in closing this functional gap, but it introduces questions regarding timing between modalities.

MethodsTo assess the effects of TSS and FES on force generation, ten neurologically intact participants underwent (1) TSS only, (2) FES only, and (3) TSS + FES. TSS was delivered using four electrodes placed at T10-T11 through the L1-L2 intervertebral spaces simultaneously, while FES was delivered to the skin over the right knee extensors and plantarflexors. For all conditions, TSS and FES were delivered using three 0.5 ms biphasic square-wave pulses at 15 Hz. During the TSS + FES condition, timing between the two modalities was adjusted in increments of [1/4] time between pulses (16.5 ms).

ResultsWhen TSS preceded FES, a larger force production was observed. We also determined several changes in muscle activation amplitude at different relative stimulus intervals, which help characterize our finding and indicate the facilitating and inhibitory effects of the modalities.

ConclusionsUtilizing a delay ranging from 15 to 30 ms between stimuli resulted in higher mean force generation in both the knee and ankle joints, regardless of the selected FES location (Average; knee: 112.0%, ankle: 103.1%).

Age, Sex and Alzheimer's disease: A longitudinal study of 3xTg-AD mice reveals sex-specific disease trajectories and inflammatory responses mirrored in postmortem brains from Alzheimer's patients
Background Aging and sex are major risk factors for developing late-onset Alzheimer's disease. Compared to men, women are not only nearly twice as likely to develop Alzheimer's, but they also experience worse neuropathological burden and cognitive decline despite living longer with the disease. It remains unclear how and when sex differences in biological aging emerge and contribute to Alzheimer's disease pathogenesis. We hypothesized that these differences lead to distinct pathological and molecular Alzheimer's disease signatures in males and females, which could be harnessed for therapeutic and biomarker development. Methods We aged male and female, 3xTg-AD and B6129 (WT) control mice across their respective lifespans while longitudinally collecting brain, liver, spleen, and plasma samples (n=3-8 mice per sex, strain, and age group). We performed histological analyses on all tissues and assessed neuropathological hallmarks of Alzheimer's disease, markers of hepatic inflammation, as well as splenic mass and morphology. Additionally, we measured concentrations of cytokines, chemokines, and growth factors in the plasma. We conducted RNA sequencing (RNA-Seq) analysis on bulk brain tissue and examined differentially expressed genes (DEGs) between 3xTg-AD and WT samples and across ages in each sex. We also examined DEGs between clinical Alzheimer's and control parahippocampal gyrus brain tissue samples from the Mount Sinai Brain Bank (MSBB) study in each sex. Results 3xTg-AD females significantly outlived 3xTg-AD males and exhibited progressive Alzheimer's neuropathology, while 3xTg-AD males demonstrated progressive hepatic inflammation, splenomegaly, circulating inflammatory proteins, and next to no Alzheimer's neuropathological hallmarks. Instead, 3xTg-AD males experienced an accelerated upregulation of immune-related gene expression in the brain relative to females, further suggesting distinct inflammatory disease trajectories between the sexes. Clinical investigations revealed that 3xTg-AD brain aging phenotypes are not an artifact of the animal model, and individuals with Alzheimer's disease develop similar sex-specific alterations in canonical pathways related to neuronal signaling and immune function. Interestingly, we observed greater upregulation of complement-related gene expression, and lipopolysaccharide (LPS) was predicted as the top upstream regulator of DEGs in diseased males of both species. Conclusions Our data demonstrate that chronic inflammation and complement activation are associated with increased mortality, revealing that age-related changes in immune response act as a primary driver of sex differences in Alzheimer's disease trajectories. We propose a model of disease pathogenesis in 3xTg-AD males in which aging and transgene-driven disease progression trigger an inflammatory response, mimicking the effects of LPS stimulation despite the absence of infection.

In vivo validation of late-onset Alzheimer's disease genetic risk factors
Introduction: Genome-wide association studies have identified over 70 genetic loci associated with late-onset Alzheimer's disease (LOAD), but few candidate polymorphisms have been functionally assessed for disease relevance and mechanism of action. Methods: Candidate genetic risk variants were informatically prioritized and individually engineered into a LOAD-sensitized mouse model that carries the AD risk variants APOE4 and Trem2*R47H. Potential disease relevance of each model was assessed by comparing brain transcriptomes measured with the Nanostring Mouse AD Panel at 4 and 12 months of age with human study cohorts.Results: We created new models for 11 coding and loss-of-function risk variants. Transcriptomic effects from multiple genetic variants recapitulated a variety of human gene expression patterns observed in LOAD study cohorts. Specific models matched to emerging molecular LOAD subtypes.Discussion: These results provide an initial functionalization of 11 candidate risk variants and identify potential preclinical models for testing targeted therapeutics.

Synchronous Measurements of Extracellular Action Potentials and Neurochemical Activity with Carbon Fiber Electrodes in Nonhuman Primates
Measuring the dynamic relationship between neuromodulators, such as dopamine, and neuronal action potentials is imperative to understand how these fundamental modes of neural signaling interact to mediate behavior. Here, we developed methods to measure concurrently dopamine and extracellular action potentials (i.e., spikes) and applied these in a monkey performing a behavioral task. Standard fast-scan cyclic voltammetric (FSCV) electrochemical (EChem) and electrophysiological (EPhys) recording systems are combined and used to collect spike and dopamine signals, respectively, from an array of carbon fiber (CF) sensors implanted in the monkey striatum. FSCV requires the application of small voltages at the implanted sensors to measure redox currents generated from target molecules, such as dopamine. These applied voltages create artifacts at neighboring EPhys-measurement sensors, producing signals that may falsely be classified as physiological spikes. Therefore, simple automated temporal interpolation algorithms were designed to remove these artifacts and enable accurate spike extraction. We validated these methods using simulated artifacts and demonstrated an average spike recovery rate of 84.5%. This spike extraction was performed on data collected from concurrent EChem and EPhys recordings made in a task-performing monkey to discriminate cell-type specific striatal units. These identified units were shown to correlate to specific behavioral task parameters related to reward size and eye-movement direction. Synchronous measures of spike and dopamine signals displayed contrasting relations to the behavioral task parameters, as taken from our small set of representative data, suggesting a complex relationship between these two modes of neural signaling. Future application of our methods will help advance our understanding of the interactions between neuromodulator signaling and neuronal activity, to elucidate more detailed mechanisms of neural circuitry and plasticity mediating behaviors in health and in disease.

Significance statementWe present a simple method for recording synchronous molecular and neuronal spike signals. Conventional electrophysiological and electrochemical instruments are combined without the need for additional hardware. A custom-designed algorithm was made and validated for extracting neuronal action potential signals with high fidelity. We were able to compute cell-type specific spike activity along with molecular dopamine signals related to reward and movement behaviors from measurements made in the monkey striatum. Such combined measurements of neurochemical and extracellular action potentials may help pave the way to elucidating mechanisms of plasticity, and how neuromodulators and neurons are orchestrated to mediate behavior.

A thalamic hub of action cues coordinates early visual processing and perception
Distinguishing between sensory experiences elicited by external stimuli and an animal's own actions is critical for accurate perception. However, the diversity of behaviors and their complex influences on the senses make this distinction challenging. Here, we show that a combination of self-motion cues modulates visual processing in the superficial superior colliculus (sSC), the brain's first visual relay. We uncovered a projection from the ventral lateral geniculate nucleus to the sSC in mice that functions as a corollary discharge hub, conveying inhibitory signals about translational optic flow and motor dynamics, including saccades, locomotion, and pupil size. Activation of this projection potently dampens visual responses and concurrently drives corresponding motor actions that resemble motor prediction errors; suppression disrupts action-specific visual perception. Our results show that visual signals undergo continuous refinement at the earliest stages through the convergence of self-motion information, ensuring accurate visual perception and visuomotor control.

Decoding contextual influences on auditory perception from primary auditory cortex
Perception can be highly dependent on stimulus context, but whether and how sensory areas encode the context remains uncertain. We used an ambiguous auditory stimulus - a tritone pair - to investigate the neural activity associated with a preceding contextual stimulus that strongly influenced the tritone pair's perception: either as an ascending or a descending step in pitch. We recorded single-unit responses from a population of auditory cortical cells in awake ferrets listening to the tritone pairs preceded by the contextual stimulus. We find that the responses adapt locally to the contextual stimulus, consistent with human MEG recordings from the auditory cortex under the same conditions. Decoding the population responses demonstrates that pitch-change selective cells are able to predict well the context-sensitive percept of the tritone pairs. Conversely, decoding the distances between the pitch representations predicts the opposite of the percept. The various percepts can be readily captured and explained by a neural model of cortical activity based on populations of adapting, pitch and pitch-direction selective cells, aligned with the neurophysiological responses. Together, these decoding and model results suggest that contextual influences on perception may well be already encoded at the level of the primary sensory cortices, reflecting basic neural response properties commonly found in these areas.

Distractors induce space-specific neural biases in visual working memory
Information in working memory is remarkably resilient to distraction. Yet, recent evidence suggests that distractors containing task-relevant features can disrupt working memory by inducing subtle biases in mnemonic representations. With multivariate decoding of human electroencephalography recordings, we show that temporally unpredictable distractors produce spatially-antagonistic mnemonic biases, across the visual hemifields. Grating distractors produced either an attractive or a repulsive mnemonic bias -- a shift in the neural representation of the memorandum toward or away from the distractor's orientation -- depending, respectively, on whether the distractor appeared in the same hemifield as the memorandum, or opposite to it. Behavioral biases closely tracked these neural effects. We devised a two-tier ring attractor model with cross-hemifield inhibition, which comprehensively explains how the distractor's timing, encoding strength, and input gating control these mnemonic biases. Our results provide a mechanistic account of distractor-induced biases, across space and time, in visual working memory.

Online stimulation of the prefrontal cortex during practice increases motor variability and modulates later cognitive transfer: a randomized, double-blinded and sham-controlled tDCS study
Background: The benefits of learning a motor skill extend to improved task-specific cognitive abilities. The mechanistic underpinnings of this motor-cognition relationship potentially rely on overlapping neural resources involved in both processes, an assumption lacking causal evidence. Objectives: We hypothesize that interfering with prefrontal networks would affect concurrent motor skill performance, long-term learning and associated cognitive functions dependent on similar networks (transfer). Methods: We conducted a randomized, double-blinded, sham-controlled brain stimulation study using transcranial direct current stimulation (tDCS) in young adults spanning over three weeks to assess the role of the prefrontal regions in learning a complex balance task and long-term cognitive performance. Results: Balance training combined with active tDCS led to higher performance variability in the trained task as compared to the sham group, without affecting the learning rate. Furthermore, active tDCS also positively impacted performance in untrained motor and cognitive tasks. Conclusion: The findings of this study help ascertaining the networks directly involved in learning a complex motor task and its implications on cognitive function. Hence, opening up the possibility of harnessing the observed frontal networks involved in resource mobilization in instances of aging, brain lesion/injury or dysfunction. Keywords. Motor learning, prefrontal cortex, Transcranial direct current stimulation, transfer effects, cognition.

Sex and age independent predictive call sequence alterations of pups in an autism spectrum disorder mouse model
Social communication deficit is a hallmark of autism spectrum disorders (ASDs). Mouse ultrasonic-vocalizations (USVs), with communicative significance, are extensively used to probe vocalization-based social communication impairment. However, most studies on ASDs mouse-models show inconsistent alterations in USVs based phenotypes over age and sex. Despite the predictable nature of mouse USVs, very few studies have taken advantage of the same. The current work explores USV pup-isolation-call (PIC) features and alterations in structural content of predictive PIC sequences of the well-established in-utero valproic-acid (VPA) exposure-based ASDs model. Our study shows the importance of higher-order USV structures, with speech-like sequential dependencies that have consistent alterations in ASDs model at all developmental ages and sex. In addition to confirming prior observations of reduced call rates and durations, as well as heightened peak frequencies in ASD model pups, our data underscores inconsistent trends in the call features across sex and age. The varying nature of call features in ASD models poses a substantial challenge in assessing intervention outcomes. The above inconsistency complicates the differentiation between the effects of aging and therapeutic impacts. Establishing consistent alteration in USVs could help uncover age- and sex-independent changes in ASD models, shedding light on associated therapeutics and developmental mechanisms.