bioRxiv Subject Collection: Neuroscience's Journal

Cholecystokinin input from the anterior cingulate cortex to the lateral periaqueductal gray mediates nocebo pain behavior in mice
The nocebo effect, the evil twin of the better-known placebo effect in which anticipation of harm causes that harm, is increasingly thought to be responsible for poor clinical outcomes. In humans, nocebo hyperalgesia (i.e., increased sensitivity to pain) is blocked by proglumide, a cholecystokinin (CCK) receptor antagonist. Yet the neural circuitry underlying nocebo hyperalgesia remains unidentified, largely due to lack of appropriate animal models. Independently, our two laboratories developed unique animal models of CCK-dependent nocebo hyperalgesia in which expectation of pain resulted from environmental or social cues. We find that both nocebo paradigms share a neural circuit involving CCK release from neurons projecting from the anterior cingulate cortex to the lateral periaqueductal gray. This pathway, which had not been previously recognized, could represent a promising target for therapeutic interventions in pain-related disorders.

Sex differences in progressive multiple sclerosis brain gene expression in oligodendrocytes and OPCs
Multiple sclerosis is a neurological autoimmune disease with sex-imbalanced incidence; in the USA, the disease is more likely to affect females at a ratio of 3:1. In addition, males are more likely to have a more severe disease course at time of diagnosis. Questions about both causes and downstream effects of this disparity remain. We aim to investigate gene expression differences at a cellular level while considering sex to discover fine-scale sex disparities. These investigations could provide new avenues for treatment targeting, or treatment planning based on sex. Public single-nuclei RNA-sequencing data from three publications of progressive MS including control brains were analysed using the Seurat R package. Differential gene and pathway expression was looked at both within a specific data set which has sub-lesion level sample dissection and across all studies to provide a broader lens. This allowed for the consideration of cell types and spatial positioning in relation to the interrogated lesion in some of the calculations. Our analysis showed expression changes in the female MS oligodendrocytes and oligodendrocyte progenitor cells compared to healthy controls, which were not observed in the corresponding male affected cells. Differentially up-regulated genes in females include increased HLA-A in the oligodendrocytes, and increased clusterin in the oligodendrocyte progenitor cells. There are also several mitochondrial genes in both the oligodendrocytes and oligodendrocyte progenitors which are up-regulated in females, including several directly involved in electron transport and which have previously been associated with neurodegenerative diseases. These results point to altered states in oligodendrocyte progenitors and oligodendrocytes that in combination with known physiological dissimilarities between sexes may denote different programming in males and females in response to the onset of demyelinating lesions. The potential for increased debris clearance mediated by clusterin and availability of oligodendrocyte progenitors in females may indicate an environment more primed for repair, potentially including remyelination. This could contribute to the disparity in etiology in females versus males.

BTK-NLRP3-Caspase1 and Gasdermin D-Caspase 11 pathways jointly drive neuroinflammation and functional impairments in a rat model of psychosocial stress
Abstract Common psychological disorders related to stress, depression and anxiety pose serious disease and economic burden globally and especially in lower and lower middle-income countries. Existing pharmacotherapies mostly target neurotransmitter systems and are partially effective across a range of diagnostic categories. However, it is also a long-standing finding that a low-grade inflammation in persistently present in systemic circulation as well as in the brain in stress, depression and anxiety. Specifically, neuroinflammation driven by Interleukin-1{beta} (IL-1{beta}) a pleiotropic cytokine, has been the focus of keen interest in this regard. IL1{beta} is a master regulator of neuroinflammation and has long been associated with these neuropsychiatric conditions. Earlier, several studies have shown the induction of IL1{beta} from its precursor pro IL-1{beta} in vivo in models of anxiogenic stress, cleaved by caspase 1, through the activation of a large multiprotein complex known as the NLRP3 inflammasome complex. However, underlying mechanism of its release from the cells is not well understood. Using rat models of physical and psychosocial stress, we first validated stress-mediated induction of IL1{beta} along with NLRP3/caspase 1, the canonical inflammasome mediators. In addition, we observed stress-indued upregulation of activated caspase 11 and Gasdermin D N-terminal fragments, the mediators of non-canonical inflammasome pathway, which facilitates the release of IL1{beta} through pore formations in the plasma membrane. Inhibition of caspase 11 with wedelolactone significantly reduced stress-induced elevation of IL1{beta} levels, attenuated anxiety-like behaviors, and improved working memory. Similarly, blocking of Gasdermin D cleavage by disulfiram, a FDA approved drug, reduced IL1{beta} levels and improved recovery from stress-induced behavior deficits. Combination treatments targeting both canonical (ibrutinib for pBTK/NLRP3 or MCC950 for NLRP3 inhibition) and non-canonical (wedelolactone for caspase 11 or disulfiram for gasdermin D) pathways, proved more efficacious in reducing stress-mediated neuroinflammation, synaptic elimination in CA3 region of hippocampus, and reducing behavioral dysfunction across several domains of behavior . Furthermore, psychosocial stress augmented peripheral inflammation, as evidenced by elevated Gasdermin D and caspase 11 in PBMCs, which was mitigated by this combination treatment. Taken together, this study provides strong evidence that psychosocial stress induces both canonical as well non-canonical inflammasome pathways, first processing Pro IL1{beta} to active IL-{beta} and second, facilitating its release from the cells.These jointly contribute to the exacerbated anxious behavior and working memory deficits in rat-models of stress. Here we are reporting for the first time the non-canonical activation of caspase 11 and Gasdermin D cleavage in brain and peripheral immune cells following psychosocial stress. Our data provides robust preclinical data and argues for amelioration of the NLRP3 inflammasome dependent IL-1{beta} release to be considered as an alternative transdiagnostic therapeutic strategy in stress, depression and anxiety.

Decoding continuous goal-directed movement from human brain-wide intracranial recordings.
Reaching out your hand is an effortless yet complex behavior that is indispensable in daily life. Restoring arm functionality is therefore rated a top priority by people with tetraplegia. Recently, neural correlates of movement have been observed and decoded beyond the motor cortex, but the degree and granularity of movement representation is not fully understood. Here, we explore the neural content of brain-wide movement-related neural activity by decoding neural correlates into 12 different kinematics of goal-directed reaching behavior. Eighteen participants implanted with stereotactic electroencephalography electrodes performed a gamified 3D goal-directed movement task. We demonstrate that continuous movement kinematics can be decoded from distributed recordings using low, mid and high frequency information in all participants using preferential subspace identification (PSID). The neural correlates of movement were distributed throughout the brain, including deeper structures such as the basal ganglia and insula. Moreover, we show that hand position could only be decoded using a goal-directed reference frame, indicating that widespread low-frequency activity is involved in higher-order processing of movements. Our results strengthen the evidence that widespread motor-related dynamics exist across numerous brain regions and can be used to continuously decode movement. The results may provide new opportunities for motor brain-computer interfaces for individuals with a compromised motor cortex, e.g. after stroke, or for control signals in adaptive closed-loop systems.

Single-cell Transcriptomics Unravel Stereocilia Degeneration as a Key Contributor to Age-related Vestibular Dysfunction in Mice and Humans
Age-related vestibular dysfunction (ARVD) is a prevalent, debilitating condition in the elderly. The etiology and molecular mechanisms are poorly understood. We focused on mechanosensitive hair cells (HCs) as they are particularly vulnerable to aging. Using single-cell RNA-seq transcriptomes of young and old mouse vestibular HCs, we show that aging HCs display both universal molecular blueprints, such as genomic instability, mitochondrial dysfunction, and impaired proteostasis, and cell type-specific aging signatures associated with deterioration of hair bundles and mechanotransduction. These signatures are also observed in aged human vestibular HCs, suggesting shared mechanisms. Importantly, morphological and functional analysis revealed that bundle degeneration and vestibular functional decline precede HC loss, highlighting the deterioration of mechanotransduction as a key contributor to ARVD. Furthermore, molecular and cellular changes associated with aging signatures are less pronounced in vestibular HCs than in cochlear HCs, underscoring the different pace of aging between the two mammalian inner ear sensory epithelia.

Interferometric Ultra-High Resolution 3D Imaging through Brain Sections
Single-molecule super-resolution microscopy allows pin-pointing individual molecular positions in cells with nanometer precision. However, achieving molecular resolution through tissues is often difficult because of optical scattering and aberrations. We introduced 4Pi single-molecule nanoscopy for brain with in-situ point spread function retrieval through opaque tissue (4Pi-BRAINSPOT), integrating 4Pi single-molecule switching nanoscopy with dynamic in-situ coherent PSF modeling, single-molecule compatible tissue clearing, light-sheet illumination, and a novel quantitative analysis pipeline utilizing the highly accurate 3D molecular coordinates. This approach enables the quantification of protein distribution with sub-15-nm resolution in all three dimensions in complex tissue specimens. We demonstrated 4Pi-BRAINSPOT's capacities in revealing the molecular arrangements in various sub-cellular organelles and resolved the membrane morphology of individual dendritic spines through 50-m transgenic mouse brain slices. This ultra-high-resolution approach allows us to decipher nanoscale organelle architecture and molecular distribution in both isolated cells and native tissue environments with precision down to a few nanometers.

Nutritionally responsive PMv DAT neurons are dynamically regulated during pubertal transition
Pubertal development is tightly regulated by energy balance. The crosstalk between metabolism and reproduction is orchestrated by complex neural networks and leptin action in the hypothalamus plays a critical role. The ventral premammillary nucleus (PMv) leptin receptor (LepRb) neurons act as an essential relay for leptin action on reproduction. Here, we show that mouse PMv cells expressing the dopamine transporter (DAT) gene, Slc6a3 (PMvDAT) form a novel subpopulation of LepRb neurons. Virtually all PMvDAT neurons expressed Lepr mRNA and responded to acute leptin treatment. Electrophysiological recordings from DATCRE;tdTomato mice showed that PMvDAT cells in prepubertal females have a hyperpolarized resting membrane potential compared to diestrous females. Slc6a3 mRNA expression in the PMv was higher in prepubertal than in adult females. In prepubertal females Slc6a3 mRNA expression was higher in overnourished females from small size litters than in controls. Prepubertal Lepob females showed decreased PMv Slc6a3 mRNA expression, that recovered to control levels after 3 days of leptin injections. Using a tracer adenoassociated virus in the PMv of adult DATCre;Kiss1hrGFP females, we observed PMvDAT projections in the anteroventral periventricular and periventricular nucleus (AVPV/PeN), surrounding Kiss1hrGFP neurons, a population critical for sexual maturation and positive estrogen feedback in females. The DATCRE;tdTomato projections to the AVPV were denser in adult than in prepubertal females. In adults, they surrounded tyrosine hydroxylase neurons. Overall, these findings suggest that the DAT expressing PMvLepRb subpopulation play a role in leptin regulation of sexual maturation via actions on AVPV kisspeptin/tyrosine hydroxylase neurons.

Centella asiatica improves sleep quality and quantity in aged mice
Age-related sleep disruption is common in older adults. Not only does the total amount of time spent in sleep decline, but the number of arousals during sleep increases with age. As sleep is important for both memory consolidation and to prevent neurodegenerative pathology, this decline in sleep and/or sleep consolidation may underlie age-related cognitive decline and dementias. Furthermore, treatment of sleep disruption can improve quality of life. However, few interventions have successfully reversed age-related sleep decline. Extracts from the plant Centella asiatica have demonstrated neuroprotective effects in human, rodent, and fly models of aging and neurodegenerative diseases, and is a promising intervention for dementias, yet little is known about how these extracts affect sleep patterns. Here, we administered Centella asiatica water extract (CAW) dosed or control chow to male and female C57BL6/J mice aged 18 months. Effects on sleep composition were determined using electrodes that recorded EEG and EMG signals. We found that CAW dosed chow (1000 mg/kg/day) increased REM sleep time in aged male mice and decreased the number of arousals during sleep observed in aged females, compared to age- and sex-matched controls. We conclude that CAW administered in food has a moderate, sex-dependent effect on sleep quantity and quality.

Age and Learning Shapes Sound Representations in Auditory Cortex During Adolescence
Adolescence is a developmental period characterized by heightened plasticity, yet how ongoing development affects sensory processing and cognitive function is unclear. We investigated how adolescent (postnatal day 40) and adult (postnatal day 80) mice differ in performance on a pure tone Go/NoGo auditory discrimination task of varying difficulty. Using dense electrophysiological recordings, we measured spiking activity at single neuron resolution in the auditory cortex while mice were engaged in the task. Adolescent mice showed lower auditory discrimination performance compared to adults, particularly in more challenging versions of the discrimination. This performance difference was due to higher response variability and weaker cognitive control expressed as lower response bias. Adolescent and adult neuronal responses differed only slightly in representations of pure tones when measured outside the context of learning and the task. However, cortical representations after learning within the context of the task were markedly different. We found differences in stimulus- and choice-related activity at the single neuron level representations, as well as lower population-level decoding in adolescents. Overall, cortical decoding in adolescents was lower and slower, especially for difficult sound discrimination, reflecting immature cortical representations of sounds and choices. Notably, we found age-related differences, which were higher after learning, reflecting the combined impact of age and learning. Our findings highlight distinct neurophysiological and behavioral profiles in adolescence, underscoring the ongoing development of cognitive control mechanisms and cortical plasticity during this sensitive developmental period.

Multivariate Neural Markers of Individual Differences in Thought Control Difficulties
Difficulties in controlling thought, including pathological rumination, worry, and intrusive thoughts, occur in a range of mental health disorders. Here we identify specific patterns of brain activity distributed within and across canonical brain networks that are associated with self-reported difficulties in controlling one's thoughts. These activity patterns were derived using multivariate pattern analysis on fMRI data recorded while participants engaged in one of four operations on an item in working memory: maintaining it, replacing it with another, specifically suppressing it, or clearing the mind of all thought. Individuals who reported greater difficulties exhibited brain activation patterns that were more variable and less differentiated across the four operations in frontoparietal and default mode networks, and showed less distinct patterns of connectivity within the default mode network. These activity profiles were absent during rest but serve as promising task-based neural markers, explaining over 30% of the variance in thought control difficulties.

Anti-Parkinsonian Drugs Rescue Locomotor Deficits in JIP3 Knockout Zebrafish: Implications for Treating Patients with MAPK8IP3-related Neurodevelopmental Disorders
MAPK8IP3-related neurodevelopmental disorders are a spectrum of rare conditions caused by de novo mutations in the MAPK8IP3 gene that encodes the JIP3 protein. These disorders are associated with a spectrum of neurodevelopmental symptoms that manifest in children and cause brain abnormalities, profound intellectual disabilities, movement disorders, and developmental delays. JIP3 is required for axonal transport of proteins and organelles between the soma and the synaptic terminal of neurons, a process critical for normal brain development and function. Homozygous loss-of-function mutations in JIP3 lead to impaired axonal transport and aggregation of cargo, which result in axonal swelling and stunted elongation. Despite these severe outcomes, disease mechanisms are poorly understood, and no current treatments are available. Here we conduct thorough morphological, behavioral, and motility phenotyping in the JIP3 knockout zebrafish and identify locomotor deficits and morphological abnormalities. To identify treatment options, we used insights from expert clinicians and the artificial intelligence tool, mediKanren, to identify drug candidates hypothesized to improve patient symptoms or compensate for the loss of JIP3 at the molecular level. We then prioritized drugs that are FDA-approved, safe for children, and readily available. These collective efforts identified amantadine and levodopa as candidate therapies and rescued motor phenotypes associated with JIP3 loss-of-function in zebrafish.

Functional Interrogation of Neuronal Subtypes via Intersectional Expression of Optogenetic Actuator Reveals Non-linear Components in a Linear Circuit
Investigating signal integration in a neural circuit is oftentimes challenging when the circuit contains neuronal subtypes that are transcriptomically similar, due to the lack of tools to express optogenetic actuators with high cellular specificity and to deliver light with high spatiotemporal accuracy. Here, we demonstrate the use of a split GAL4-based genetic "AND" gate to express Chrimson in specific touch receptor neuron (TRN) subtypes in the C. elegans touch response circuit. Combining this intersectional strategy for transgene expression with high-throughput optical targeting and behavioral quantification, we optogenetically interrogated the role of each TRN subtype in mediating the mechanosensor-induced escape response and in integrating signals that trigger the opposite motor output. Surprisingly, we found that although the response of the overall circuit linearly combines the competing anterior and posterior stimuli, this linearity is comprised of antagonistic non-linear contributions from the anterior and posterior sensors, which conspire to generate a linear response.

A Generalist Intracortical Motor Decoder
Mapping the relationship between neural activity and motor behavior is a central aim of sensorimotor neuroscience and neurotechnology. While most progress to this end has relied on restricting complexity, the advent of foundation models instead proposes integrating a breadth of data as an alternate avenue for broadly advancing downstream modeling. We quantify this premise for motor decoding from intracortical microelectrode data, pretraining an autoregressive Transformer on 2000 hours of neural population spiking activity paired with diverse motor covariates from over 30 monkeys and humans. The resulting model is broadly useful, benefiting decoding on 8 downstream decoding tasks and generalizing to a variety of neural distribution shifts. However, we also highlight that scaling autoregressive Transformers seems unlikely to resolve limitations stemming from sensor variability and output stereotypy in neural datasets. Code: https://github.com/joel99/ndt3

Ontogeny of catechol-o-methyltransferase expression in the rat prefrontal cortex: effects of methamphetamine exposure
Repeated use of methamphetamine (METH) is known to dysregulate the dopaminergic system and induce long-lasting changes in behavior, which may be influenced by sex and age of exposure. Catechol-o-methyltransferase (COMT) is an enzyme that is involved in the breakdown of catecholamines, and its role in dopamine clearance is thought to be especially important in the prefrontal cortex (PFC) where dopamine transporter (DAT) expression is relatively scarce. The first study in this report utilized a rat model to characterize the ontogeny of COMT protein expression in the PFC and nucleus accumbens (NAc) across adolescence, which is a developmental stage that has been shown to involve significant reorganization of dopaminergic innervation. Drug-naive male and female Sprague-Dawley rats were sacrificed on postnatal day (P) 29, 39, 49 or 69, and expression levels of COMT protein within the PFC and NAc were analyzed via Western blot. We found that COMT expression in the PFC increases across adolescence in a sex-dependent manner but does not significantly change in the NAc during this timeframe. A separate group of rats were injected daily from P40-48 (adolescence) or P70-78 (adulthood) with saline or 3.0 mg/kg METH and sacrificed on P49 or P79. While METH decreased COMT in adult rats of both sexes, METH increased COMT expression in the PFC of rats exposed in adolescence. The results of this work suggest that exposure to METH during adolescence uniquely effects dopamine clearance within the PFC, potentially contributing to differences in neurobiological outcomes from METH use.

BMAL1 Overexpression in Suprachiasmatic Nucleus Protects from Retinal Neurovascular Deficits in Diabetes
The suprachiasmatic nucleus (SCN) regulates circadian rhythms and influences physiological and behavioral processes. Disruptions in circadian rhythms (CRD) are observed in type 2 diabetes (T2D), and importantly, CRD acts as an independent risk factor for T2D and its associated complications. BMAL1, a circadian clock gene, is vital for sustaining an optimal circadian rhythm and physiological function. However, the therapeutic potential of BMAL1 overexpression in the SCN to rectify the neurovascular deficits of T2D has yet to be investigated. In this study, db/db mice, a well-established model of T2D exhibiting arrhythmic behavior and the complications of diabetes, were injected stereotaxically with AAV8-Bmal1 or a control virus in the SCN to evaluate the protective effects of correcting the central clock on neurovascular deficits. Given the complex neurovascular network and the eyes unique accessibility as a transparent system, ocular complications were selected as a model to examine the neuronal functional, behavioral, and vascular benefits of correcting the central clock. BMAL1 overexpression normalized the circadian rhythms, as demonstrated by improvements in the free-running period. The retinal neuronal function improved on electroretinogram, along with optomotor behavior and visual acuity enhancements. Retinal vascular deficits were also significantly reduced. Notably, our approach helped decrease fat content in genetically predisposed obese animals. Since the SCN is known to regulate hepatic glucose production via sympathetic mechanisms, glycemic control, and pyruvate tolerance tests were conducted. Systemically, we observed improved glucose homeostasis in BMAL1-overexpressing mice alongside a substantial reduction in hepatic gluconeogenesis. BMAL1 overexpression lowered plasma norepinephrine and liver TH levels, indicating a protective regulation of adrenergic signaling. Thus, this study underscores the therapeutic potential of targeting circadian clock genes like BMAL1 in the SCN to alleviate metabolic and neurovascular deficits associated with T2D. Our research offers a compelling framework for integrating circadian rhythms into managing diabetes and its complications.

A Mean-Field Approach to Criticality in Spiking Neural Networks for Reservoir Computing
Reservoir computing is a neural network paradigm for processing temporal data by exploiting the dynamics of a fixed, high-dimensional system, enabling efficient computation with reduced complexity compared to fully trainable recurrent networks. This work presents an analytical framework for configuring in the critical regime a reservoir based on spiking neural networks with a highly general topology. Specifically, we derive and solve a mean-field equation that governs the evolution of the average membrane potential in leaky integrate-and-fire neurons, and provide an approximation for the critical point. This framework reduces the need for an extensive online fine-tuning, offering a streamlined path to near-optimal network performance from the outset. Through extensive simulations, we validate the theoretical predictions by analyzing the network's spiking dynamics and quantifying its computational capacity using the information-based Lempel-Ziv-Welch complexity near criticality. Finally, we explore self-organized quasi-criticality by implementing a local learning rule for synaptic weights, demonstrating that the network's dynamics remain close to the theoretical critical point. Beyond AI, our approach and findings also have significant implications for computational neuroscience, providing a principled framework for quantitatively understanding how biological networks leverage criticality for efficient information processing.

Neuronal Silencing and Protection in a Mouse Model of Demyelination
Damage to the myelin sheath that protects axons in the central nervous system is a hallmark pathology of demyelinating diseases like multiple sclerosis. Cuprizone-induced demyelination in mice is a common model for studying demyelination and remyelination. However, the relationship between myelin damage and recovery and the functional properties of ensheathed neurons remains poorly understood. Using concurrent monitoring of hippocampal myelination and neuronal firing rates in the same mouse, we assessed longitudinal changes during cuprizone consumption and remyelination treatment. The data revealed a rapid decline in neuronal activity that preceded myelin loss. Females showed a more severe decrease after 4 days of cuprizone, which correlated with enhanced neuronal activity and myelin loss 51 days later, whereas male mice showed a more severe decline in neuronal activity after 55 days of cuprizone. Following cuprizone cessation, mice were treated with Clemastine or vehicle for 45 days. A short-term recovery was found in both groups, before the Clemastine group showed increased remyelination and higher neuronal firing rates. The mean increase and decrease in firing rates were proportional to the same-neuron baseline firing rate in the Clemastine and vehicle groups, respectively, highlighting a potential linkage between the status of myelin recovery and cellular activity.

Vascular amyloidβ load in the meningeal arterial network correlates with loss of cerebral blood flow and pial collateral vessel enlargement in the J20 murine model of Alzheimer's disease
INTRODUCTION: Global reduction in cerebral blood flow (CBF) is an early pathology in Alzheimer's disease, preceding significant plaque accumulation and neurological decline. Chronic reduced CBF and subsequent reduction in tissue oxygenation and glucose may drive neurodegeneration, yet the underlying cause of globally reduced CBF remains unclear. METHODS: Using premortem delivery of Methoxy-XO4 to label A{beta}, and arterial vascular labeling, we assessed A{beta} burden on the pial artery/arteriole network and cerebral blood flow in aged male and female WT and J20 AD mice. RESULTS: The pial artery/arteriole vascular network selectively displayed extensive vascular A{beta} burden. Pial collateral arteriole vessels, the by-pass system that reroutes blood flow during occlusion, displayed significant enlargement in J20 mice. Despite this, CBF was decreased by approximately 15% in 12-month J20 mice when compared to WT littermates. DISCUSSION: Significant A{beta} burden on the meningeal arterial network may contribute to the restriction of CBF. Redistribution of CBF through enlarged pial collateral vessels may serve as a compensatory mechanism to alter CBF during disease progression in cases of CAA.

Neuropixels Opto: Combining high-resolution electrophysiology and optogenetics
High-resolution extracellular electrophysiology is the gold standard for recording spikes from distributed neural populations, and is especially powerful when combined with optogenetics for manipulation of specific cell types with high temporal resolution. We integrated these approaches into prototype Neuropixels Opto probes, which combine electronic and photonic circuits. These devices pack 960 electrical recording sites and two sets of 14 light emitters onto a 1 cm shank, allowing spatially addressable optogenetic stimulation with blue and red light. In mouse cortex, Neuropixels Opto probes delivered high-quality recordings together with spatially addressable optogenetics, differentially activating or silencing neurons at distinct cortical depths. In mouse striatum and other deep structures, Neuropixels Opto probes delivered efficient optotagging, facilitating the identification of two cell types in parallel. Neuropixels Opto probes represent an unprecedented tool for recording, identifying, and manipulating neuronal populations.

The impact of perturbation intensity schedule on improvements in reactive balance control in young adults: an experimental study
Background: Reactive balance training (RBT) uses unanticipated perturbations to improve balance reactions and prevent falls. Intensity and predictability of perturbations may affect the generalizability of RBT, but their relative contributions remain unclear. This study aimed to compare the effects of three RBT schedules with differing intensity and predictability on participants' balance recovery following untrained perturbations, and to determine perceived difficulty and challenge of the training schedules. Methods: Participants were 36 healthy young adults (20-35 years). Participants were randomly assigned to one of three RBT intensity schedules (fixed high intensity, low-to-high intensity, and variable intensity). Training took place on a motion platform that delivered perturbations in varying directions (forward, backward, left, and right) and intensities across five trial blocks. Balance reactions (number of recovery steps) pre- and post-training, and electrodermal responses, and perceived difficulty during training were collected. Statistical analyses compared post-training outcomes between training groups, controlling for the baseline value. Results: Participants took fewer steps and decreased the proportion of multi-step reactions pre- to post-training (p<0.0001), with no significant between-group differences. Perceived exertion decreased significantly across training blocks in the fixed-high group and increased significantly in the low-to-high group. Electrodermal responses declined across all groups between training blocks 1 and 3 (p=0.017). Conclusions: Improvements in step reactions to untrained perturbations did not differ between training groups, highlighting the importance of multi-directional variability over specific intensity schedules for enhancing balance recovery.

Single-nucleus analysis reveals dysregulated oxidative phosphorylation in Down syndrome basal forebrain at birth
Basal forebrain cholinergic neurons (BFCNs) are integral to learning, attention, and memory, and are prone to degeneration in Down syndrome (DS), Alzheimers disease, and other neurodegenerative diseases. However, the mechanisms that lead to degeneration of these neurons are not known. Single-nuclei gene expression and ATAC sequencing were performed on postmortem human basal forebrain from unaffected control and DS tissue samples at 0-2 years of age (n=4 each). Sequencing analysis of postmortem human basal forebrain identifies gene expression differences in early postnatal DS early in life. Genes encoding proteins associated with energy metabolism pathways, specifically oxidative phosphorylation and glycolysis, and genes encoding antioxidant enzymes are upregulated in DS BFCNs. Multiomic analyses reveal that energy metabolism may be disrupted in DS BFCNs by birth. Increased oxidative phosphorylation and the accumulation of reactive oxygen species byproducts may be early contributors to DS BFCN neurodegeneration.

A single low-dimensional neural component of motor unit activity explains force generation across repetitive isometric tasks
Previous studies suggest that low-dimensional control underlies motor unit activity, with low-frequency oscillations in common synaptic inputs serving as the primary determinant of muscle force production. In this study, we used principal component analysis (PCA) and factor analysis (FA) to investigate the relationship between low-dimensional motor unit components and force oscillations during repetitive isometric tasks with similar force profiles. We assessed the consistency of these components across trials in both individual (tibialis anterior; first dorsal interosseous) and synergistic muscles (vastus medialis, VM; vastus lateralis, VL). Participants performed 15 trials of a force-matching learning task. Three post-skill acquisition trials were selected for analysis to ensure high similarity in force profiles. Motor units were decomposed from high-density surface electromyograms, tracked across trials, and their smoothed discharge rates were decomposed into low-dimensional components using PCA and FA. Parallel analysis indicated that a single component could explain the smoothed discharge rates for the individual muscles and two components for VM-VL. Importantly, the first component explained most of the variance (~70%) in smoothed discharge rates across all muscles. The first motor unit component also showed significantly higher correlations with force oscillations than the second component and remained highly consistent across trials. These findings were further supported by a non-linear framework combining network- and information-theoretic tools, which revealed high motor unit network density in the first component of all muscles. Collectively, these results suggest that, during isometric contractions, motor unit activity is primarily controlled by a single dominant shared synaptic input that closely mirrors force oscillations.

Regulatory Network Inference of Induced Senescent Midbrain Cell Types Reveals Cell Type-Specific Senescence-Associated Transcriptional Regulators
Cellular senescence of brain cell types has become an increasingly important perspective for both aging and neurodegeneration, specifically in the context of Parkinson's Disease (PD). The characterization of classical hallmarks of senescence is a widely debated topic, whereby the context in which a senescence phenotype is being investigated, such as the cell type, the inducing stressor, and/or the model system, is an extremely important aspect to consider when defining a senescent cell. Here, we describe a cell type-specific profile of senescence through the investigation of various canonical senescence markers in five human midbrain cell lines using chronic 5-Bromodeoxyuridine (BrdU) treatment as a model of DNA damage-induced senescence. We used principal component analysis (PCA) and subsequent regulatory network inference to define both unique and common senescence profiles in the cell types investigated, as well as revealed senescence-associated transcriptional regulators (SATRs). Functional characterization of one of the identified regulators, transcription factor AP4 (TFAP4), further highlights the cell type-specificity of the expression of the various senescence hallmarks. Our data indicates that SATRs modulate cell type-specific profiles of induced senescence in key midbrain cell types that play an important role in the context of aging and PD.

Targeted inactivation of spinal α2 adrenoceptors promotes paradoxical anti-nociception
Noradrenergic drive from the brainstem to the spinal cord varies in a context-dependent manner to regulate the patterns of sensory and motor transmission that govern perception and action. In sensory networks, it is traditionally assumed that activation of spinal 2 receptors is anti-nociceptive, while spinal 2 blockade is pro-nociceptive. Here, however, we demonstrate in vivo in rats that targeted blockade of spinal 2 receptors can promote anti-nociception. The anti-nociceptive effects are not contingent upon supraspinal actions, as they persist below a chronic spinal cord injury and are enhanced by direct spinal application of antagonist. They are also evident throughout sensory-dominant, sensorimotor integrative, and motor-dominant regions of the gray matter, and neither global changes in spinal neural excitability nor off-target activation of spinal 1 adrenoceptors or 5HT1A receptors abolished the anti-nociception. Together, these findings challenge the current understanding of noradrenergic modulation of spinal nociceptive transmission.

Radiation exposure induced blood-brain barrier injury via mitochondria-mediated sterile inflammation
Radiation-induced brain injury (RIBI) is caused by exposure to high doses of ionizing radiation and characterized by severe cognitive dysfunction and brain necrosis. The widespread application of radiotherapy and rapid development of deep space exploration have substantially increased the risk of RIBI. However, the pathogenesis of RIBI is not fully understood, and no effective intervention is available. This work described a blood-brain barrier (BBB) microphysiological system (MPS), that allowed to explore the responses of BBB and distinct brain cells to radiation exposure. This BBB MPS can recapitulate the interface structure and function of BBB in brain microenvironment, including brain endothelial cells, astrocytes, pericytes and microglia co-cultured under flow condition. Following acute exposure to radiation of X-ray or {gamma}-ray, characteristic RIBI-associated pathological responses were observed, including BBB compromise, DNA breaks, inhibited cell proliferation, cell hypertrophy and pro-inflammatory cytokine release. Among the distinctive types of cells, brain endothelial cells showed the highest radiosensitivity as compared to other cells in the MPS. Intriguingly, X-ray and {gamma}-ray radiation consistently induced prominent sterile inflammation responses, especially type I interferon response, in the BBB MPS. These responses were mediated by radiation-induced mitochondrial DNA release and subsequent activation of cGAS-STING signaling pathway. Furthermore, we found abrocitinib (JAK1 inhibitor) and idebenone (mitochondrial protectant) can attenuate radiation-induced inflammation and ameliorate BBB injury. These findings revealed the involvement of mitochondria-mediated inflammation in RIBI pathogenesis, identifying mitochondria as a potential target for new radioprotective measures.

PET imaging of an antisense oligonucleotide in the living non-human primate brain using click chemistry
Determination of a drug's biodistribution is critical to ensure it reaches the target tissue of interest. This is particularly challenging in the brain where invasive sampling methods may not be possible. Here, a pretargeted imaging methodology is disclosed that utilizes bioorthogonal click chemistry to determine the distribution of an antisense oligonucleotide in the living brain following intrathecal dosing. A novel positron emission tomography (PET) tracer, [18F]BIO-687, bearing a click-reactive trans-cyclooctene (TCO) was discovered and tested in conjunction with a Malat1 antisense oligonucleotide (ASO) conjugated with a methyltetrazine (MeTz). PET imaging in rats demonstrated that the tracer possesses good kinetic properties for CNS imaging and can react to form a covalent linkage with high specificity to the MeTz-conjugated-ASO in vivo. Further, the amount of tracer reacted by cycloaddition with the Tz was determined to be dependent on the concentration of ASO-MeTz in tissue, as determined through comparison of the imaging signal with the LC-MS of the tissue homogenate. The approach was evaluated in cynomolgus monkeys, using both Malat1 and the MAPT ASO BIIB080, with PET imaging showing favorable tracer kinetics and specific binding to both ASOs in vivo. These results demonstrate that the tracer [18F]BIO-687 can image intrathecally-delivered ASO distribution in the brain, and future studies should leverage this technology to evaluate ASO distribution in human patients to study distribution.

Artificial sweeteners differentially activate sweet and bitter gustatory neurons in Drosophila
Artificial sweeteners are highly sweet, non-nutritive compounds that have become increasingly popular over recent decades despite research suggesting that their consumption has unintended consequences. Specifically, there is evidence suggesting that some of these chemicals interact with bitter taste receptors, implying that sweeteners likely generate complex chemosensory signals. Here, we report the basic sensory characteristics of sweeteners in Drosophila, a common model system used to study the impacts of diet, and find that all noncaloric sweeteners inhibited appetitive feeding responses at higher concentrations. At a cellular level, we found that sucralose and rebaudioside A co-activated sweet and bitter gustatory receptor neurons (GRNs), two populations that reciprocally impact feeding behavior, while aspartame only activated bitter cells. We assessed the behavioral impacts of sweet and bitter co-activation and found that low concentrations of sucralose signal appetitive feeding while high concentrations signal feeding aversion. Finally, silencing bitter GRNs reduced the aversive signal elicited by high concentrations of sucralose and significantly increased sucralose feeding behaviors. Together, we conclude that artificial sweeteners generate a gustatory signal that is more complex than sweetness alone, and this bitter co-activation has behaviorally relevant effects on feeding that may help flies flexibly respond to these unique compounds.

Guiding G protein signaling by target enhancement of GPCRs
Activation of G protein coupled receptors coupling to the Gi/o pathway leads to the activation of G protein-activated inward rectifier potassium channels (GIRK) in a fast membrane-delimited manner in excitable cells. Activation of GIRK causes the hyperpolarization of the cell membrane, where hyperpolarization is dependent on te availability of Gi/o coupled GPCRs and GIRK. In particular, in optogenetic and chemogenetic experiments neuronal silencing depends on downstream targets of Gi/o-coupled GPCRs. To selectively enhance Gi/o mediated GIRK currents, we created expression cassettes consisting of a homomer forming GIRK subunit and various light-activated Gi/o-coupled GPCRs (Melanopsin, Long-wave-sensitive opsin 1, Parapinopsin or Opsin 7b). We demonstrate that light-activation of the GIRK/GPCR constructs induces robust GIRK currents in human embryonic kidney 293 cells, cardiomyocytes and cerebellar Purkinje cells and changes the net effect of G protein signaling of the promiscuous Opn4L from a Gq/11 mediated excitation towards an Gi/o mediated inhibition. Thus, our tools enhance target selectivity and improve optogenetic control of the Gi/o pathway by light in excitable cells.

A conserved epilepsy-associated gene co-expression module identifies increased metabolic rate as a shared pathomechanism
Epilepsy is a mechanistically complex, incompletely understood neurological disorder. To uncover novel converging mechanisms in epilepsy, we used Drosophila whole-brain single-cell RNA-sequencing to refine and characterize a previously proposed human epilepsy-associated gene co-expression network (GCN). We identified a conserved co-expressed module of 26 genes, which comprises fly orthologs of 13 epilepsy-associated genes and integrates synaptic and metabolic functions. Over one-third of the Drosophila pan-neuronal knockdown models targeting this module exhibited altered seizure-like behaviors in response to mechanical or heat stress. These recapitulated seizures associated with four epilepsy-associated genes, identified two novel epilepsy candidate genes, and three genes knockdown of which conferred seizure protection. Most knockdown models with altered seizure susceptibility showed changes in metabolic rate and levels of phosphorylated adenosine monophosphate-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Enhancing AMPK activity increased seizure resistance in a dose-dependent manner. Our findings show that Drosophila single-cell expression data and behavior can aid functional validation of human GCNs and highlight a role for metabolism in modifying seizure susceptibility.

Computational detection, characterization, and clustering of microglial cells in a mouse model of fat-induced postprandial hypothalamic inflammation
Obesity is associated with brain inflammation, glial reactivity, and immune cells infiltration. Studies in rodents have shown that glial reactivity occurs within 24 hour of high-fat diet (HFD) consumption, long before obesity development, and takes place mainly in the hypothalamus (HT), a crucial brain structure for controlling body weight. Understanding more precisely the kinetics of glial activation of two major brain cells (astrocytes and microglia) and their impact on eating behavior could prevent obesity and offer new prospects for therapeutic treatments. To understand the mechanisms pertaining to obesity-related neuroinflammation, we developed a fully automated algorithm, NutriMorph. Although some algorithms were developed in the past decade to detect and segment cells, they are highly specific, not fully automatic, and do not provide the desired morphological analysis. Our algorithm cope with these issues and performs the analysis of cells images (here, microglia of the hypothalamic arcuate nucleus), and the morphological clustering of these cells through statistical analysis and machine learning. Using the k-Means algorithm, it clusters the microglia of the control condition (healthy mice) and the different states of neuroinflammation induced by high-fat diets (obese mice) into subpopulations. This paper is an extension and re-analysis of a first published paper showing that microglial reactivity can already be seen after few hours of high-fat diet (Cansell et al., 2021). Thanks to NutriMorph algorithm, we unravel the presence of different hypothalamic microglial subpopulations (based on morphology) subject to proportion changes in response to already few hours of high-fat diet in mice.

In the brain of the beholder: whole brain dynamics shape the perception during ambiguous motion
Visual perception typically relies on a one-to-one mapping between stimuli and conscious experiences. However, under bistable conditions, identical sensory inputs can elicit alternating perceptions, requiring the brain to resolve ambiguity. The mechanisms underlying transitions between distinct perceptual states and their sustained maintenance remain poorly understood. In this ultra-high field (7T) fMRI study, we investigated the neural dynamics of perception using a bistable motion stimulus (ambiguous motion quartet) that evoked endogenous alternations between horizontal and vertical motion, compared to a control condition (physical motion quartet) with unambiguous sensory input. Consistent with prior findings, the human motion complex (hMT+) played a central role in processing both physical and ambiguous motion conditions. By dissociating neural activity during perceptual transitions from sustained perceptions, we found that hMT+ mostly interacts dynamically with area 46 in the frontal cortex and PF/PFm within the inferior parietal lobe during transitions and with subregions of the superior parietal lobe during sustained perceptions. Beyond local activity, computational modeling revealed increased hierarchical organization across cortical networks during the ambiguous condition. Notably, the same frontal and parietal regions exhibited ascension within the functional hierarchy, likely reflecting their specific role in coordinating computations for resolving ambiguity.

Network Biomarkers of Alzheimer's Disease Risk Derived from Joint Volume and Texture Covariance Patterns in Mouse Models
Alzheimer's disease (AD) lacks effective cures and is typically detected after substantial pathological changes have occurred, making intervention challenging. Early detection and understanding of risk factors and their downstream effects are therefore crucial. Animal models provide valuable tools to study these prodromal stages. We investigated various levels of genetic risk for AD using mice expressing the three major human APOE alleles in place of mouse APOE. We leverage these mouse models utilizing high-resolution magnetic resonance diffusion imaging, due to its ability to provide multiple parameters that can be analysed jointly. We examine how APOE genotype interacts with age, sex, diet, and immunity to yield jointly discernable changes in regional brain volume and fractional anisotropy, a sensitive metric for brain water diffusion. Our results demonstrate that genotype strongly influences the caudate putamen, pons, cingulate cortex, and cerebellum, while sex affects the amygdala and piriform cortex bilaterally. Immune status impacts numerous regions, including the parietal association cortices, thalamus, auditory cortex, V1, and bilateral dentate cerebellar nuclei. Risk factor interactions particularly affect the amygdala, thalamus, and pons. APOE2 mice on a regular diet exhibited the fewest temporal changes, suggesting resilience, while APOE3 mice showed minimal effects from a high-fat diet (HFD). HFD amplified aging effects across multiple brain regions. The interaction of AD risk factors, including diet, revealed significant changes in the periaqueductal gray, pons, amygdala, inferior colliculus, M1, and ventral orbital cortex. Future studies should investigate the mechanisms underlying these coordinated changes in volume and texture, potentially by examining network similarities in gene expression and metabolism, and their relationship to structural pathways involved in neurodegenerative disease progression.

Identifying JNK-regulated phosphoproteome markers of anxiety-like behaviour in mouse hippocampus
JNKs mediate neuronal damage in neurodegenerative disease and inhibitors of JNK1 have shown anxiolytic and anti-depressive effects in mice. Here, we analyze the phosphoproteomes of hippocampus and nucleus accumbens from DJNKI-1 (JNK inhibitor)-infused mice. We correlate phospho-site changes with anxiety-like behaviours in the elevated plus maze and light-dark test and identify unique changes in responder mice. Among the DJNKI-1 regulated phosphosites, several lie within GSK3 motifs and are exclusively down-regulated. Consistent with this, GSK3{beta} is inhibited and AKT activated. Importantly, we detect multilevel regulation of glucose metabolism enzymes including increased PDPK1-S241 phosphorylation, and a 5-fold increase in pyruvate dehydrogenase (PDHA1)-S-293 phosphorylation, signifying its inhibition. This suggests that JNK inhibitor drives a metabolic transformation to the neuronal Warburg response. This and a range of identified synaptic and cytoskeletal protein phosphosite changes are discussed in the context of JNK-regulated anxiety responses. The annotated hippocampal and nucleus accumbens phosphoproteomes described here will support a mechanistic understanding of the JNK pathway for future studies of brain disorders.

Semi-automated analysis of beading in degenerating axons
Axonal beading is a key morphological indicator of axonal degeneration, which plays a significant role in various neurodegenerative diseases and drug-induced neuropathies. Quantification of axonal susceptibility to beading using neuronal cell culture can be used as a facile assay to evaluate induced degenerative conditions, and thus aid in understanding mechanisms of beading and in drug development. Manual analysis of axonal beading for large datasets is labor-intensive and prone to subjectivity, limiting the reproducibility of results. To address these challenges, we developed a semi-automated Python-based tool to track axonal beading in time-lapse microscopy images. The software significantly reduces human effort by detecting the onset of axonal swelling. Our method is based on classical image processing techniques rather than an AI approach. This provides interpretable results while allowing the extraction of additional quantitative data, such as bead density, coarsening dynamics, and morphological changes over time. Comparison of results obtained through human analysis and the software shows strong agreement. The code can be easily extended to analyze diameter information of ridge-like structures in branched networks of rivers, road networks, blood vessels, etc.

Psilocybin as a Treatment for Repetitive Mild Head Injury: Evidence from Neuroradiology and Molecular Biology
Repetitive mild head injuries incurred while playing organized sports, during car accidents and falls, or in active military service are a major health problem. These head injuries induce cognitive, motor, and behavioral deficits that can last for months and even years with an increased risk of dementia, Parkinson's disease, and chronic traumatic encephalopathy. There is no approved medical treatment for these types of head injuries. To this end, we tested the healing effects of the psychedelic psilocybin, as it is known to reduce neuroinflammation and enhance neuroplasticity. Using a model of mild repetitive head injury in adult female rats, we provide unprecedented data that psilocybin can reduce vasogenic edema, restore normal vascular reactivity and functional connectivity, reduce phosphorylated tau buildup, enhance levels of brain-derived neurotrophic factor and its receptor TrkB, and modulate lipid signaling molecules.

THE EFFECT OF SERTRALINE AND VOLUNTARY EXERCISE DURING PREGNANCY ON LITTER CHARACTERISTICS AND POSTNATAL AFFECTIVE BEHAVIOUR IN RAT DAMS
Introduction: Sertraline is the frontline pharmacotherapy for the treatment of depression and anxiety during pregnancy. However, there is little evidence regarding the effects of sertraline on maternal behaviour or the maternal brain. Furthermore, the efficacy of non-pharmacological approaches to treatment in pregnancy, such as exercise, are unclear. Therefore, the aim of this study was to examine the effects of sertraline and exercise during pregnancy on maternal postnatal depressive-like, anxiety-like and associated behaviours, as well as litter characteristics, in a rat model of depression. We also investigated the effects of these treatments on the maternal brain, focusing initially on DNA methylation and glutamatergic markers, which have been implicated in depression. Method: Twenty-four female Wistar-Kyoto (WKY; strain that models depression and anxiety) rats were divided into three groups: 1. WKY-Sertraline; 2. WKY-Exercise, 3. WKY-Vehicle; Six female Wistar rats were included as controls. Rats were treated with sertraline (10mg/kg) or vehicle (33% propylene glycol) twice/day, from gestational day (GD) 1 to postnatal day (PN) 14. The WKY-Exercise group were provided access to a running wheel during pregnancy for 3 hours/day from GD1-18. Dam and litter characteristics, as well as pup ultrasonic vocalisations (USVs), were measured. Dams underwent behavioural testing at 5-weeks postnatal to assess depressive-, anxiety- and cognitive-like behaviours. Gene expression of DNA methylation markers (Dnmt1, Dnmt3a) and glutamate receptors (Grin1, Grin2a, Grin2b) were measured in the prefrontal cortex (PFC), using RT-qPCR. Result: The WKY-Sertraline group gained 39% less weight in their first pregnancy week compared to all other groups (p<0.05) and produced smaller litters compared to Wistar controls (-43%; p=0.003) and WKY-Exercise (-38%; p=0.012), and WKY-Sertraline pups had slightly smaller brain weights (p=0.031 compared to WKY-Vehicle). The WKY-Exercise pups produced increased number of USVs at PN7 compared to WKY-Vehicle, with no treatment differences at PN14. The WKY strain however, did showed reduced average mean amplitude of calls and reduced average duration of calls at PN7 compared to WIS (p<0.01) and reduced number of calls at PN14 (p<0.01). Maternal sertraline treatment did not significantly affect dam behavioural measures, all maternal cortical gene expression. The WKY-Exercise group however showed reduced anxiety-like behaviours, spending more time in the open arms (620%; p=0.027) and less time in the closed arms (-22%; p=0.047) of the elevated plus maze (EPM) compared to WKY-Vehicle, and more time in the centre of the open field test (OFT) compared to WKY-Vehicle (132%; p=0.057). Furthermore, WKY-Exercise dams showed a 64% increase in Dnmt3a mRNA levels in the PFC compared to WKY-Vehicle (p=0.019). Conclusion: Voluntary exercise during pregnancy in the WKY rat model, reduced postnatal anxiety-like behaviour in the dam. This was accompanied by elevated DNMT3a gene expression in the PFC, suggesting this region may be sensitive to DNA methylation changes following maternal exercise. In contrast, maternal sertraline did not impact these behaviours or genes. Maintaining sertraline treatment beyond PN14, may have resulted in broader effects on dam behaviour, which should be explored further. Maternal sertraline did appear to have some adverse effects on the in utero environment, evidenced by smaller litters, with slightly smaller pup brain weights, which should be investigated further. Our findings suggest a long-term beneficial effect of exercise during pregnancy and supports future studies examining the effects of exercise in antenatal depression in the human population.

Modular architecture confers robustness to damage and facilitates recovery in spiking neural networks modeling in vitro neurons
Impaired brain function is restored following injury through dynamic processes that involve synaptic plasticity. This restoration is supported by the brains inherent modular organization, which promotes functional separation and redundancy. However, it remains unclear how the modular structure interacts with synaptic plasticity, most notably in the form of spike-timing-dependent plasticity (STDP), to define the damage response and recovery efficiency. In this work, we numerically modeled the response and recovery to damage of a neuronal network in vitro bearing a modular structure. Consistent with the in vitro observations, the in silico numerical model effectively captured the decline and subsequent recovery of spontaneous activity following the injury. We revealed that the modular structure confers robustness to injury, minimizes the decrease in neuronal activity, and promotes recovery via STDP. Finally, using the reservoir computing framework, we show that information representation in the neuronal network improves with the recovery of synchronous activity. Our work provides an experimental-numerical platform for predicting recovery in damaged neuronal networks and may help developing effective models for brain injury.

The role of human intraparietal sulcus in evidence accumulation revealed by EEG and model-informed fMRI
Sequential sampling models propose that the repeated sampling of sensory information is a fundamental component of perceptual decision-making. Electroencephalographic investigations in humans have demonstrated motor-independent representations of evidence accumulation, but such observations have seldom been made in neuroimaging studies exploring the neuroanatomical origins of evidence accumulation. Here, we aimed to reveal the neuroanatomical locus of sensory evidence accumulation in the human brain by regressing an electrophysiological marker of evidence accumulation (centroparietal positivity, CPP) against changes in blood oxygen level-dependent (BOLD) signal during perceptual decision-making. Our cross-modal imaging approach revealed a cluster within left intraparietal sulcus (IPS), located within putative lateral intraparietal area (region hIP3), for which BOLD signals scaled in relation to the slope of the CPP. Furthermore, the drift rate parameter of a drift diffusion model parametrically modulated BOLD activity within an overlapping region of left IPS. In contrast, parametric modulation by reaction time revealed a distributed fronto-parietal network, demonstrating the utility of our approach for isolating a discrete neuroanatomical locus of evidence accumulation. Together, our findings provide strong support for intraparietal sulcus involvement in the accumulation of sensory evidence during human perceptual decision-making.

Sphingosine-1-phosphate signaling through Müller glia regulates neuroprotection and the accumulation of immune cells in the rodent retina
The purpose of this study was to investigate how Sphingosine-1-phosphate (S1P) signaling regulates glial phenotype, neuroprotection, and reprogramming of Muller glia (MG) into neurogenic MG-derived progenitor cells (MGPCs) in the adult mouse retina. We found that S1P-related genes were dynamically regulated following retinal damage. S1pr1 (encoding S1P receptor 1) and Sphk1 (encoding sphingosine kinase 1) are expressed at low levels by resting MG and are rapidly upregulated following acute damage. Overexpression of the neurogenic bHLH transcription factor Ascl1 in MG downregulates S1pr1, and inhibition of Sphk1 and S1pr1/3 enhances Ascl1-driven differentiation of bipolar-like cells and suppresses glial differentiation. Treatments that activate S1pr1 or increase retinal levels of S1P initiate pro-inflammatory NF{kappa}B-signaling in MG, whereas treatments that inhibit S1pr1 or decreased levels of S1P suppress NF{kappa}B-signaling in MG in damaged retinas. Conditional knock-out of NF{kappa}B-signaling in MG increases glial expression of S1pr1 but decreases levels of S1pr3 and Sphk1. Conditional knock-out (cKO) of S1pr1 in MG, but not Sphk1, enhances the accumulation of immune cells in acutely damaged retinas. cKO of S1pr1 is neuroprotective to ganglion cells, whereas cKO of Sphk1 is neuroprotective to amacrine cells in NMDA-damaged retinas. Consistent with these findings, pharmacological treatments that inhibit S1P receptors or inhibit Sphk1 had protective effects upon inner retinal neurons. We conclude that the S1P-signaling pathway is activated in MG after damage and this pathway acts secondarily to restrict the accumulation of immune cells, impairs neuron survival and suppresses the reprogramming of MG into neurogenic progenitors in the adult mouse retina.

The effects of reliable social feedback on language learning: insights from EEG and pupillometry
Language learning is often a social process, and social feedback may play a motivational role. We examined the neurophysiological correlates of word learning with feedback varying in reliability and social content. Participants associated novel auditory words with objects and received social (video clips) or symbolic (static images) feedback. In a forced-choice task, participants learned to associate novel auditory words with known objects and received feedback that was either Social Reliable (correct), Social Unreliable (random), or Symbolic Reliable (correct). Post-training behavioral performance was better for words learned with social and symbolic reliable feedback. Stimulus-preceding negativity (SPN) and late positive complex (LPC) ERP amplitudes, as well as pupil dilation, showed differences as a function of feedback reliability and social content. In the reliable conditions, before feedback, SPN amplitude grew as learning progressed, likely due to the expectation of receiving positive feedback. During feedback, LPC amplitude for positive feedback diminished as learning progressed but not for negative feedback, which was likely consistently used for context updating. These effects were not observed for unreliable feedback, probably because its value was not used for updating information. Pupillometry results corroborated these findings, showing greater dilation for negative vs positive feedback in reliable conditions. Finally, when feedback was social, processing was associated with more frontal activation and behavioral performance was closely correlated with both ERP and pupillometry results. Overall, our findings show differential processing of feedback depending on its informational and social content, advancing our understanding of how social and cognitive processes interact to shape word learning.

Differentiating unirradiated mice from those exposed to conventional or FLASH radiotherapy using MRI
Background and purpose: The FLASH effect expands the therapeutic ratio of tumor control to normal tissue toxicity observed after delivery of ultra-high (>100 Gy/s FLASH-RT) vs. conventional dose rate radiation (CONV-RT). In this first exploratory study, we assessed whether ex-vivo Magnetic Resonance Imaging (MRI) could reveal long-term differences after FLASH-RT and CONV-RT whole-brain irradiation. Materials and methods: Female C57BL/6 mice were divided into three groups: control (non-irradiated), conventional (CONV-RT 0.1 Gy/s), and ultra-high dose rates (FLASH-RT 1 pulse, 5.5 x 10^6 Gy/s), and received 10 Gy of whole-brain irradiation in a single fraction at 10 weeks of age. Mice were evaluated by Novel Object Recognition cognitive testing at 10 months post-irradiation and were sampled at 13 months post-irradiation. Ex-vivo brains were imaged with a 14.1 Tesla/26 cm magnet with a multimodal MRI protocol, including T2-weighted TurboRare (T2W) and diffusion-weighted imaging (DWI) sequences. Results: In accordance with previous results, cognitive tests indicated that animals receiving CONV-RT exhibited a decline in cognitive function, while FLASH-RT performed similarly to the controls. MRI showed decreased hippocampal mean intensity in the CONV-RT mice compared to controls but not in the FLASH-RT group. Comparing CONV-RT to control, we found significant changes in multiple whole-brain diffusion metrics, including the mean Apparent Diffusion Coefficient (ADC) and Mean Apparent Propagator (MAP) metrics. By contrast, no significant diffusion changes were found between the FLASH-RT and control groups. In an exploratory analysis compared to controls, regional diffusion metrics were primarily altered in the basal forebrain and the insular cortex after CONV-RT, and after FLASH-RT, a trend reduction was also observed. Conclusion: This study presents initial evidence that MRI can uncover clear changes in the brain after CONV-RT but not after FLASH-RT. The MRI results aligned with the observed cognitive protection after FLASH-RT, indicating the potential use of MRI to analyze the FLASH response.

Protein Synthesis Blockade Prevents Fear Memory Reactivation via Inhibition of Engram Synapse Strengthening
Memory relies on ensembles of engram cells in the brain. While previous studies have established the existence of these cells, the relationship between cellular and synaptic activity remains unclear. To address this, we applied the dual e-GRASP technique in mice to examine synaptic connectivity between the ventral CA1 and the basal amygdala during memory formation. We found that contextual fear conditioning increased engram-to-engram synapse (engram synapse) density and induced structural potentiation, highlighting their importance in associative memory. Additionally, we investigated the role of protein synthesis in memory formation by inducing retrograde amnesia using anisomycin, a protein synthesis inhibitor. Single anisomycin-injected mice (1xANI) showed impaired natural recall but still displayed fear responses upon optogenetic reactivation of engram cells. In contrast, mice that received four anisomycin injections over six hours (4xANI) showed significantly impaired natural recall and failed to exhibit fear responses upon optogenetic reactivation. This behavioural phenotype was correlated with synaptic changes as 1xANI mice exhibited no significant reduction in engram synapse density but had significantly smaller spine size while 4xANI mice showed both significant reduction in engram synapse density and spine size. Our result indicate that protein synthesis inhibition significantly changes engram synapse density and spine size which correlatively affect fear memory natural recall and artificial reactivation.

Cerebral blood perfusion across biological systems and the human lifespan
Blood perfusion delivers oxygen and nutrients to all cells, making it a fundamental feature of brain organization. How cerebral blood perfusion maps onto micro-, meso- and macro-scale brain structure and function is therefore a key question in neuroscience. Here we analyze pseudo-continuous arterial spin labeling (ASL) data from 1 305 healthy individuals in the HCP Lifespan studies (5-100 years) to reconstruct a high-resolution normative cerebral blood perfusion map. At the cellular and molecular level, cerebral blood perfusion co-localizes with granular layer IV, biological pathways for maintenance of cellular relaxation potential and mitochondrial organization, and with neurotransmitter and neuropeptide receptors involved in vasomodulation. At the regional level, blood perfusion aligns with cortical arealization and is greatest in regions with high metabolic demand and resting-state functional hubs. Looking across individuals, blood perfusion is dynamic throughout the lifespan, follows microarchitectural changes in development, and maps onto individual differences in physiological changes in aging. In addition, we find that cortical atrophy in multiple neurodegenerative diseases (late-onset Alzheimers disease, TDP-43C, and dementia with Lewy bodies) is most pronounced in regions with lower perfusion, highlighting the utility of perfusion topography as an indicator of transdiagnostic vulnerability. Finally, we show that ASL-derived perfusion can be used to delineate arterial territories in a data-driven manner, providing insights into how the vascular system is linked to human brain function. Collectively, this work highlights how cerebral blood perfusion is central to, and interlinked with, multiple structural and functional systems in the brain.

Spatiotemporal Patterns Differentiate Hippocampal Sharp-Wave Ripples from Interictal Epileptiform Discharges in Mice and Humans
Hippocampal sharp-wave ripples (SPW-Rs) are high-frequency oscillations critical for memory consolidation in mammals. Despite extensive characterization in rodents, their application as biomarkers to track and treat memory dysfunction in humans is limited by coarse spatial sampling, interference from interictal epileptiform discharges (IEDs), and lack of consensus on human SPW-R localization and morphology. We demonstrate that mouse and human hippocampal ripples share spatial, spectral and temporal features, which are clearly distinct from IEDs. In 1024-channel hippocampal recordings from APP/PS1 mice, SPW-Rs were distinguishable from IEDs by their narrow localization to the CA1 pyramidal layer, narrowband frequency peaks, and multiple ripple cycles on the unfiltered local field potential. In epilepsy patients, ripples showed similar narrowband frequency peaks and visible ripple cycles in CA1 and the subiculum but were absent in the dentate gyrus. Conversely, IEDs showed a broad spatial extent and wide-band frequency power. We introduce a semi-automated, human ripple detection toolbox ('ripmap') selecting optimal detection channels and separating event waveforms by low-dimensional embedding. Our approach improves ripple detection accuracy, providing a firm foundation for future human memory research.

Phenotypic and Functional Alterations in Peripheral Blood Mononuclear Cell-Derived Microglia in a Primate Model of Chronic Alcohol Consumption
Alcohol-induced dysregulation of microglial activity is associated with neuroinflammation, cognitive decline, heightened risk for neurodegenerative diseases, alcohol dependence, and escalation of alcohol drinking. Given the challenge of longitudinally sampling primary microglia, we optimized an in vitro method to differentiate peripheral blood mononuclear cells (PBMC) from non-human primates (NHP) into microglia-like cells (induced-microglia; iMGL). The iMGLs displayed transcriptional profiles distinct from those of monocyte progenitors and closely resembling those of primary microglia. Notably, morphological features showed that differentiated iMGLs derived from NHPs with chronic alcohol consumption (CAC) possessed a more mature-like microglial morphology. Additionally, dysregulation in key inflammatory and regulatory markers alongside increased baseline phagocytic activity was observed in CAC-derived IMGLs in the resting state. Phenotypic and functional assessments following LPS stimulation indicated the presence of an immune-tolerant phenotype and enrichment of a CD86+ hyper-inflammatory subpopulation in iMGLs derived from ethanol-exposed animals. Collectively, these findings demonstrate that in vitro differentiation of PBMC offers a minimally invasive approach to studying the impact of CAC on microglial function revealing that CAC reshapes both functional and transcriptional profiles of microglia.

Neuro-behavioral impact of Tourette-related striatal disinhibition in rats
Tourette syndrome has been linked to reduced GABAergic inhibition, so called neural disinhibition, in the dorsal striatum. Dorsal-striatal neural disinhibition in animal models, caused by local microinfusion of GABA-A-receptor antagonists, produces striatal local field potential (LFP) spike-wave discharges and tic-like movements resembling motor tics. Here, we characterized further the neuro-behavioral impact of striatal disinhibition, by unilateral picrotoxin infusion into the anterior dorsal striatum, in adult male Lister hooded rats. In vivo electrophysiology under anesthesia revealed enhanced neuronal burst firing in the striatum, alongside spike-wave LFP discharges. In freely moving rats, striatal picrotoxin reliably induced tic-like movements, which mainly involved lifting of the contralateral forelimb and concomitant rotational movements of head and torso, as well as occasional rotations of the whole body around its long axis. Prepulse inhibition (PPI) of the acoustic startle response was not affected, but startle reactivity tended to be reduced. Both locomotor and non-ambulatory movements, measured in photo-beam cages, were increased. Our findings suggest that, apart from generating tic-like movements, dorsal striatal disinhibition may contribute to hyperactivity, which is often comorbid with Tourette syndrome. Enhanced striatal burst firing may be important for these behavioral effects. Our findings do not support that striatal disinhibition contributes to PPI disruption, which has been associated with Tourette syndrome and suggested to contribute to tic generation.

Significance StatementStriatal disinhibition has been implicated in tic generation. Using a rat model, we show that a key neural effect of striatal disinhibition is enhanced firing of striatal neurons in bursts. We also characterized further the tic-like movements caused by unilateral disinhibition of the anterior dorsal striatum. These mainly involved lifting of the contralateral forelimb and concomitant rotational movements of head and torso, as well as occasional rotations of the whole body around its long axis. Striatal disinhibition did not affect prepulse inhibition (PPI) but caused locomotor hyperactivity. This suggests that striatal disinhibition may contribute to the general hyperactivity often comorbid with Tourette syndrome, but that other brain mechanisms underlie the PPI deficits that have been reported in the condition.

A DC-sensitive video/electrophysiology monitoring unit for long-term continuous study of seizures and seizure-associated spreading depolarization in a rat model
There has been a long-term need for a low-cost, highly efficient, and high-fidelity epilepsy monitoring unit (EMU) suitable for home-cage monitoring of small-animal models of epilepsy. We show an accessible, scalable, highly space and energy-efficient EMU capable of fulfilling chronic, continuous synchronized multiple animal monitoring jobs. Each rig within the EMU can provide 16-channel high-fidelity, DC-sensitive biopotential recordings, head acceleration monitoring, synchronized voltammetry applications, and video recording on one freely moving rat. We present the overall EMU architecture design and subsystem details in each recording rig. We demonstrate long-term continuous in vivo recordings of spontaneous seizure and seizure-associated spreading depolarization (SD) from freely moving rats prepared under the tetanus toxin model of temporal lobe epilepsy.

Significance StatementLong-term continuous DC-sensitive biopotential and video recordings are essential for capturing the dynamics of epileptic seizures and seizure-related spreading depolarizations (SD), providing a deeper understanding of their underlying mechanisms. These recordings are invaluable for developing animal models of epilepsy, studying seizure prediction, drug testing, and investigating related neurological conditions such as mental health, aging, and dementia. They also reveal rare phenomena that short-duration recordings might miss. However, traditional methods are resource intensive. The new epilepsy monitoring unit (EMU) introduced in this paper offers a cost-effective and space-saving solution for high-fidelity chronic monitoring of freely moving animals, utilizing compact single-board computers and standard cages without interrupting the recordings.

Topological Analysis of Macaca mulatta's Cortical Structures Through the Lens of Poincare Duality
Poincare duality from algebraic topology describes how shapes and spaces interrelate across different dimensions, linking structures of one scale to complementary structures at another. This suggests that densely packed neurons in certain brain areas may correspond to broader connectivity patterns, balancing local processing with global communication. Applying this framework to cortical histological images of Macaca mulatta, we analysed neuronal clustering, connectivity graphs and intensity distributions to identify self-dual structural patterns and reveal the contribution of local organization to large-scale network activity. Using image processing techniques such as contrast enhancement, edge detection and graph-theoretic modeling, we examined how dense neuron clusters correspond to functionally sparse regions and vice versa. We found that high-density neuronal zones form closed-loop topological structures that correspond to homology cycles, while sparser areas function as large-scale integrators, aligning with cohomology properties. Local connectivity hubs in neuron-dense regions support regional specialization, while large-scale, sparser areas, though less connected, facilitate global communication by acting as pathways for long-range integration. Graph-theoretic analysis of connectivity patterns confirmed a reciprocal relationship between clustering coefficients and global centrality. Statistical analysis using Kolmogorov-Smirnov tests revealed conserved topological distributions across different cortical regions, supporting the hypothesis that cortical connectivity maintains structural invariance under local perturbations. These findings provide insights into the mathematical principles governing brain architecture, suggesting that topological methods can enhance our understanding of cortical function. Future research may extend these approaches to higher-dimensional embeddings, network theory in primate brains, functional neuroimaging, human disease modeling and artificial intelligence.

Population-level morphological analysis of paired CO2- and odor-sensing olfactory neurons in D. melanogaster via volume electron microscopy
Dendritic morphology is a defining characteristic of neuronal subtypes. In Drosophila, heterotypic olfactory receptor neurons (ORNs) expressing different receptors display diverse dendritic morphologies, but whether such diversity exists among homotypic ORNs remains unclear. Using serial block-face scanning electron microscopy on cryofixed tissues, we analyzed the majority of CO2-sensing neurons (ab1C) and their odor-sensing neighbors (ab1D) in the D. melanogaster antenna. Surprisingly, ab1C neurons featured flattened, sheet-like dendrites--distinct from the cylindrical branches typical of odor-sensing neurons--and displayed remarkable diversity, ranging from plain sheets to tube-like structures that enclose several neighboring dendrites, forming "dendrite-within-dendrite" structures. Similarly, ab1D dendrites varied from simple, unbranched forms to numerously branched morphologies. These findings suggest that morphological heterogeneity is common even among homotypic ORNs, potentially expanding their functional adaptability and ranges of sensory physiological properties.

Sex-biased zinc responses modulate ribosome biogenesis, protein synthesis and social defects in Cttnbp2 mutant mice
Autism spectrum disorders (ASD) are neurodevelopmental conditions influenced by genetic mutations, dietary factors, and sex-specific mechanisms, yet the interplay of these factors remains elusive. Here, we investigate the sex-biased responses of mutant mice carrying an ASD-associated mutation in Cttnbp2 to dietary zinc supplementation using behavioral assays, proteomic and bioinformatic analyses, and puromycin pulse labeling to assess protein synthesis. Our results demonstrate that zinc supplementation enhances ribosome biogenesis and increases the density and size of dendritic spines in male Cttnbp2 mutant mice, alleviating male-biased social deficits. Analyses of neuronal cultures further revealed that neurons, not astrocytes, respond to zinc to enhance protein synthesis. In contrast, female Cttnbp2 mutants exhibit resilience to differential zinc intake, even under zinc deprivation. Elevated mTOR phosphorylation and increased protein levels of translational initiation factors in female brains may provide a protective mechanism, reducing their sensitivity to zinc deficiency. Cttnbp2 mutations heighten male vulnerability to zinc deprivation, impairing social behaviors. These findings highlight zinc-regulated ribosome biogenesis and protein synthesis as critical mediators of sex-specific ASD phenotypes, offering new insights into dietary interventions.

Loss of white matter tracts and persistent microglial activation in the chronic phase of ischemic stroke in female rats and the effect of miR-20a-3p treatment
Our previous studies showed that intravenous injections of the small non-coding RNA mir-20a-3p is neuroprotective for stroke in the acute phase and attenuates long-term cognitive impairment in middle-aged female rats. In this study, we evaluated postmortem brain pathology at 100+d after stroke in a set of behaviorally characterized animals. This included Sham (no stroke) controls or stroke animals that received either mir20a-3p at 4h, 24h and 70d iv post stroke (MCAo+mir20a-3p) or a scrambled oligo (MCAo+Scr). Brain volumetric features were analyzed with T2 weighted and Diffusion Tensor magnetic resonance imaging (MRI) followed by histological analysis. Principal component analysis of Fractional Anisotropy (FA)-diffusion tensor MRI measures showed that MCAo+Scr and MCAo+mir20a-3p groups differed significantly in the volume of white matter but not gray matter. Weil myelin-stained sections confirmed decreased volume of the corpus callosum, internal capsule and the anterior commissure in the ischemic hemisphere of MCAo+Scr animals compared to the non-ischemic hemisphere, while sham and MCAo+Mir-20a-3p showed no hemispheric asymmetries. The MCAo+Scr group also exhibited asymmetry in hemisphere and lateral ventricle volumes, with ventricular enlargement in the ischemic hemisphere as compared to the non-ischemic hemisphere. The numbers of microglia were significantly elevated in white matter tracts in the MCAo+Scr group, with a trend towards increased myelin phagocytic microglia in these tracts. Regression analysis indicated that performance on an episodic memory test (novel object recognition test; NORT) was associated with decreased white matter volume and increased microglial numbers. These data support the hypothesis that stroke-induced cognitive impairment is accompanied by white matter attrition and persistent microglial activation and is consistent with reports that cognitive deterioration resulting from vascular diseases, such as stroke, is associated with secondary neurodegeneration in regions distal from the initial infarction.

Peri-somatic modulation of diffracted light and its variation with consciousness
Existing noninvasive neurophysiological recording methods can acquire neuronal correlates of consciousness, but they do not differentiate between conscious and unconscious states mechanistically. Here we describe a method that detects a new physical effect of apparent neural origin in the peri-somatic space that might allow such differentiation. This effect is a slow decrease in the intensity of diffracted low power laser light emitted within a photoelectronic device placed close to the body of an awake subject. It is markedly attenuated by general anesthesia in mice and unconsciousness in patients. Its direction is reversed when the device is exposed to live invertebrates or to the decapitated head of a euthanized mouse. These findings reveal a previously unrecognized biophysical phenomenon that appears to be related to consciousness.

Dose-dependent changes in global brain activity and functional connectivity following exposure to psilocybin: a BOLD MRI study in awake rats.
Psilocybin is a hallucinogen with complex neurobiological and behavioral effects. This is the first study to use MRI to follow functional changes in brain activity in response to different doses of psilocybin in fully awake, drug naive rats. Female and male rats were given IP injections of vehicle or psilocybin in doses of 0.03 mg/kg, 0.3 mg/kg, and 3.0 mg/kg while fully awake during the imaging session. Changes in BOLD signal were recorded over a 20 min window. Data for resting state functional connectivity were collected approximately 35 min post injection All data were registered to rat 3D MRI atlas with 173 brain regions providing site-specific changes in global brain activity and changes in functional connectivity. Treatment with psilocybin resulted in a significant dose-dependent increase in positive BOLD signal. The areas most affected by the acute presentation of psilocybin were the somatosensory cortex, basal ganglia and thalamus. Females were significantly more sensitive to the 0.3 mg/kg dose of psilocybin than males. There was a significant dose-dependent global increase in functional connectivity, highlighted by hyperconnectivity to the cerebellum. Brain areas hypothesized to be involved in loss of sensory filtering and organization of sensory motor stimuli such as the claustrum and the cortico-basal ganglia-thalamic-cortical loop were all affected by psilocybin in a dose-dependent manner. Indeed, the general neuroanatomical circuitry associated with the psychedelic experience was affected but the direction of the BOLD signal and pattern of activity between neural networks was inconsistent with the human literature.

Novel neurofilament light (Nefl) E397K mouse models of Charcot-Marie-Tooth type 2E (CMT2E) present early and chronic axonal neuropathy
Charcot-Marie-Tooth (CMT) is the most common hereditary peripheral neuropathy with an incidence of 1:2,500. CMT2 clinical symptoms include distal muscle weakness and atrophy, sensory loss, toe and foot deformities, with some patients presenting with reduced nerve conduction velocity. Mutations in the neurofilament light chain (NEFL) gene result in a specific form of CMT2 disease, CMT2E. NEFL encodes the protein, NF-L, one of the core intermediate filament proteins that contribute to the maintenance and stability of the axonal cytoskeleton. To better understand the underlying biology of CMT2E disease and advance the development of therapeutics, we generated a Nefl+/E397K mouse model. While the Nefl+/E397K mutation is inherited in a dominant manner, we also characterized NeflE397K/E397K mice to determine whether disease onset, progression or severity would be impacted. Consistent with CMT2E, lifespan was not altered in these novel mouse models. A longitudinal electrophysiology study demonstrated significant in vivo functional abnormalities as early as P21 in distal latency, compound muscle action potential (CMAP) amplitude and negative area. A significant reduction in the sciatic nerve axon area, diameter, and G-ratio was also present as early as P21. Evidence of axon sprouting was observed with disease progression. Through the twelve months measured, disease became more evident in all assessments. Collectively, these results demonstrate an early and robust in vivo electrophysiological phenotype and axonal pathology, making Nefl+/E397K and NeflE397K/E397Kmice ideal for the evaluation of therapeutic approaches.

Atypical plume-like events drive glutamate accumulation in metabolic stress conditions
Neural glutamate homeostasis plays a key role in health and disease. In ischemic conditions, such as stroke, this homeostasis is severely disrupted since energy depletion and ion imbalances lead to more glutamate release and less uptake. We here used the fluorescent glutamate sensor SF-iGluSnFR(A184V) to probe the effects of chemical ischemia on extracellular glutamate dynamics in situ, using organotypic slice cultures from mouse cortex. SF-iGluSnFR imaging reported spontaneous glutamate release events, which indicate synchronous network activity, similar to calcium signals detected with GCaMP6f. In addition, glutamate imaging revealed local, asynchronous release events, which were atypically large and long-lasting and showed plume-like characteristics. Under baseline conditions plumes occurred with low frequency, were independent of network activity, and persisted in the presence of TTX. Plume induction was strongly favored by blocking glutamate uptake with TFB-TBOA, whereas blocking ionotropic glutamate receptors (iGluRs) suppressed plumes. Upon inducing chemical ischemia plumes became more pronounced and overly abundant, which resulted in large-scale accumulation of extracellular glutamate. Similar plumes were recently also observed in models of cortical spreading depression and migraine. We therefore propose that plumes represent a more general phenomenon induced by glutamate uptake dysfunction, which may contribute to glutamate-related excitotoxicity in various neurodegenerative and neurological disorders.

How do egocentric boundary cells depend upon the coordinate system of environmental features?
Neurons in the retrosplenial (RSC) (Alexander et al., 2020a; LaChance and Hasselmo, 2024) and postrhinal cortex (POR) respond to environmental boundaries and configurations in egocentric coordinates relative to an animals current position. Neurons in these structures and adjacent structures also respond to spatial dimensions of self- motion such as running velocity (Carstensen et al., 2021; Robinson et al., 2024). Data and modeling suggest that these responses could be essential for guiding behaviors such as barrier avoidance and goal finding (Erdem and Hasselmo, 2012; 2014). However, these findings still leave the unanswered question: What are the features and what are the coordinate systems of these features that drive these egocentric neural responses? Here we present models of the potential circuit mechanisms generating egocentric responses in RSC. These can be generated based on coding of internal representations of barriers in head-centered coordinates of distance and angle that are transformed based on current running velocity for trajectory planning and obstacle avoidance. This hypothesis is compared with an alternate potentially complementary hypothesis that neurons in the same regions might respond to retinotopic position of features at the top, bottom or edges of walls as a precursor to head-centered coordinates. Alternate hypotheses include the forward scanning of trajectories (ray tracing) to test for collision with barriers, or the comparison of optic flow on different sides of the animal. These hypotheses generate complementary modeling predictions about how changes in environmental parameters could alter the neural responses of egocentric boundary cells that are presented here.

Serial Dependence Predicts Generalization in Perceptual Learning
Recent visual experiences systematically bias current perceptual reports, a phenomenon known as serial dependence. This study examines how serial dependence interacts with perceptual learning, specifically focusing on its role in learning generalization. We reanalyzed data from 50 observers who practiced the texture discrimination task (TDT) under three conditions designed to modulate learning generalization: consistent target location, alternating two target locations, and mixed with targetless trials (Harris et al., 2012); over 200,000 trials. Our analysis revealed substantial report biases toward the orientation of targets from previous trials, extending up to 10 trials back, much longer than previously reported. These biases, when accumulated across consistent trial sequences, nearly overshadowed responses to the current target. Remarkably, although TDT thresholds improved by 40% over the 8 days of training, the biases persisted despite the randomization of target orientations, with trial history being irrelevant to the current trial. The effect was most pronounced when current targets had low visibility, prior targets were highly visible, and prior targets appeared at the same location as the current target. Training conditions that facilitated learning generalization exhibited stronger and longer serial dependence effects from distant trial histories compared to conditions promoting specific learning. Across observers, stronger serial dependence from distant history was associated with greater learning transfer, suggesting that distant memory traces are essential for efficient learning. We propose that these extended memory traces integrate information across multiple trials to create a generalized learning template, preventing overfitting to specific stimuli thus enhancing learning transfer. In contrast, strong adaptation in the consistent target location condition disrupts these traces, thereby limiting generalization.

Neural responses in early, but not late, visual cortex are well predicted by random-weight CNNs with sufficient model complexity
Convolutional neural networks (CNNs) were inspired by the organization of the primate visual system, and in turn have become effective models of the visual cortex, allowing for accurate predictions of neural stimulus responses. While training CNNs on brain-relevant object-recognition tasks may be an important pre-requisite to predict brain activity, the CNN's brain-like architecture alone may already allow for accurate prediction of neural activity. Here, we evaluated the performance of both task-optimized and brain-optimized convolutional neural networks (CNNs) in predicting neural responses across visual cortex, and performed systematic architectural manipulations and comparisons between trained and untrained feature extractors to reveal key structural components influencing model performance. For human and monkey area V1, random-weight CNNs employing the ReLU activation function, combined with either average or max pooling, significantly outperformed other activation functions. Random-weight CNNs matched their trained counterparts in predicting V1 responses. The extent to which V1 responses can be predicted correlated strongly with the neural network's complexity, which reflects the non-linearity of neural activation functions and pooling operations. However, this correlation between encoding performance and complexity was significantly weaker for higher visual areas that are classically associated with object recognition, such as monkey IT. To test whether this difference between visual areas reflects functional differences, we trained neural network models on both texture discrimination and object recognition tasks. %, and analyzed the relationship between model complexity and task performance. Consistent with our hypothesis, model complexity correlated more strongly with performance on texture discrimination than object recognition. Our findings indicate that random-weight CNNs with sufficient model complexity allow for comparable prediction of V1 activity as trained CNNs, while higher visual areas require precise weight configurations acquired through training via gradient descent.

Striatal and cerebellar interactions during reward-based motor performance
Goal-directed motor performance relies on the brain's ability to distinguish between actions that lead to successful and unsuccessful outcomes. The basal ganglia (BG) and cerebellum (CBL) are integral to processing performance outcomes, yet their functional interactions remain underexplored. This study scanned participants' brains with functional magnetic imaging (fMRI) while they performed a skilled motor task for monetary rewards, where outcomes depended on their motor performance and also probabilistic events that were not contingent on their performance. We found successful motor outcomes increased activity in the ventral striatum (VS), a functional sub-region of the BG, whereas unsuccessful motor outcomes engaged the CBL. In contrast, for probabilistic outcomes unrelated to motor performance, the BG and CBL exhibited no differences in activity between successful and unsuccessful outcomes. Dynamic causal modeling revealed that VS-to-CBL connectivity was inhibitory following successful motor outcomes, suggesting that the VS may suppress CBL error processing for correct actions. Conversely, CBL-to-VS connectivity was inhibitory after unsuccessful motor outcomes, potentially preventing reinforcement of erroneous actions. Additionally, interindividual differences in task preference, assessed by having participants choose between performing the motor task or flipping a coin for monetary rewards, were related to inhibitory VS-CBL connectivity but not activity within the VS or CBL directly. These findings highlight a performance-mediated functional network between the VS and CBL, modulated by motivation and subjective preferences, supporting goal-directed behavior.

A wireless, 60-channel, AI-enabled neurostimulation platform
Electrical stimulation of the human brain has emerged as a powerful therapeutic modality, enabling the alteration of neural circuits underlying cognition and behavior. Recent evidence indicates that stimulation's effects on physiology and behavior depend on endogenous variation in brain state, as measured by field-potential recordings. Here, we describe a 60-channel brain-computer interface -- the Smart Neurostimulation System (SNS) -- that combines closed-loop analysis of spectral features of the field potential with multi-channel stimulation capabilities. We demonstrate system functionality via bench tests and from an in vivo ovine study exercising a subset of the device's functionality. Our ovine study shows that the SNS can reliably measure neural correlates of behavior (motion) and the physiological effects of stimulation. We demonstrate the safety of stimulation via histology following a 120-day stimulation study.

A scotophobic response characterised by body contraction and ciliary arrest in Acropora coral larvae
The motile planula larva of the reef-building coral Acropora millepora exhibits a distinct scotophobic response characterized by full-body contraction and ciliary arrest when exposed to abrupt light dimming. Through behavioural assays, we confirmed reductions in larval swimming speed and alterations in vertical and horizontal movement patterns under alternating light and dark conditions. High-speed microscopic imaging revealed that ciliary activity ceases upon light dimming, while the body contracts into a rounded shape, influencing swimming behaviour. These responses suggest an adaptive mechanism for maintaining optimal positioning within the highly structured and complex light environment of reef habitats, critical for coral recruitment and survival.

Successive failure triggered by motor exploration in a reinforcement-based reaching task
Motor exploration, a key process in reinforcement-based motor learning, is triggered by suboptimal performance and leads to increased movement variability. Consequently, failure in one trial may increase the likelihood of failure in subsequent trials. If this pattern emerges, successive failures (SFs) are not merely events to be avoided but part of the trial-and-error process of identifying optimal movements, which can facilitate motor learning. This study investigated whether and how SFs occur above chance levels during a motor learning task with binary success/failure feedback and explored the relationship between SFs and motor learning outcomes. Thirty-three healthy young adults participated in the study, performing a reaching task to pass through a target without visual feedback of their hand position. Binary feedback was provided after each trial, indicating whether the hand trajectory overlapped with the target. The results showed that the probability of two SFs was significantly higher than the square of the overall failure probability, indicating that failure streaks occurred above chance levels. A computational model, in which motor variability comprised constant motor noise and exploratory variability regulated by recent reward history (where variability increased following failure), successfully explained SF emergence. However, the learning index, defined as the difference in failure probability between the first and latter halves of the experiment, was unrelated to SF emergence. Additionally, failure streaks disappeared when participants were asked to reach one of seven randomly selected targets in each trial, suggesting that introducing environmental variability can help alleviate SFs.

Homeostasis After Injury: How Intertwined Inference and Control Underpin Post-Injury Pain and Behaviour
Injuries are an unfortunate but inevitable fact of life, leading to an evolutionary mandate for powerful homeostatic processes of recovery and recuperation. The physiological responses of the body and the immune system must be coordinated with behaviour to allow protected time for this to happen and to prevent further damage to the affected bodily parts. Reacting appropriately requires an internal control system that represents the nature and state of the injury and specifies and withholds actions accordingly. We bring the formal uncertainties embodied in this system into the framework of a partially observable Markov decision process (POMDP). We discuss nociceptive phenomena in light of this analysis, noting particularly the paradoxical behaviours associated with injury investigation, and the propensity for transitions from normative, tonic, to pathological, chronic, pain states. Importantly, these simulation results provide a quantitative account and enable us to sketch a much-needed roadmap for future theoretical and experimental studies on injury, tonic pain, and transition to chronic pain. Ultimately, we seek novel ways to target chronic pain.

Ubiquitin Proteasome System Components, RAD23A and USP13, Modulate TDP-43 Solubility and Neuronal Toxicity
At autopsy, >95% of ALS cases display a redistribution of the essential RNA binding protein TDP-43 from the nucleus into cytoplasmic aggregates. The mislocalization and aggregation of TDP-43 is believed to be a key pathological driver in ALS. Due to its vital role in basic cellular mechanisms, direct depletion of TDP-43 is unlikely to lead to a promising therapy. Therefore, we have explored the utility of identifying modifier genes that modify its mislocalization or aggregation. We have previously shown that loss of rad-23 improves locomotor deficits in TDP-43 C. elegans models of disease and increases the degradation rate of TDP-43 in cellular models. To understand the mechanism through which these protective effects occur, we generated an inducible mutant TDP-43 HEK293 cell line. We find that knockdown of RAD23A reduces insoluble TDP-43 levels in this model and primary rat cortical neurons expressing human TDP-43A315T. Utilizing a discovery-based proteomics approach, we then explored how loss of RAD23A remodels the proteome. Through this proteomic screen, we identified USP13, a deubiquitinase, as a new potent modifier of TDP-43 induced aggregation and cytotoxicity. We find that knockdown of USP13 reduces the abundance of sarkosyl insoluble mTDP-43 in both our HEK293 model and primary rat neurons, reduces cell death in primary rat motor neurons, and improves locomotor deficits in C. elegans ALS models.

Noradrenaline and Acetylcholine shape Functional Connectivity organization of NREM substages: an empirical and simulation study
Sleep onset is characterized by a departure from arousal, and can be separated into well-differentiated stages: NREM (which encompasses three substages: N1, N2 and N3) and REM (Rapid Eye Movement). Awake brain dynamics are maintained by various wake-promoting mechanisms, particularly the neuromodulators Acetylcholine (ACh) and Noradrenaline (NA), whose levels naturally decrease during the transition to sleep. The combined influence of these neurotransmitters on brain connectivity during sleep remains unclear, as previous models have examined them mostly in isolation or only in deep sleep. In this study, we employ a Whole Brain model to investigate how changes in brain neurochemistry during NREM sleep, specifically involving ACh and NA, affect the Functional Connectivity (FC) of the brain. Using a Wilson-Cowan whole brain model informed by an empirical connectome and a heterogeneous receptivity map of neuromodulators, we explore these dynamics. Initial FC analysis reveals distinct connectivity changes: a decrease in Locus Coeruleus (LC) connectivity with the cortex during N2 and N3, and a decrease in Basal Forebrain (BF) connectivity with the cortex during N3. Additionally, compared to Wakefulness (W), there is a transition to a more integrated state in N1 and a more segregated state in N3. We adjust the coupling and input-output slope of the Whole Brain model for ACh and NA, based on BF or LC priors, to show that region-specific neurotransmitter distribution is key to explaining their effects on FC. This work enhances our understanding of neurotransmitters' roles in modulating sleep stages and their significant contribution to brain state transitions between different states of consciousness, both in health and disease.

Down syndrome with Alzheimers disease brains have increased iron and associated lipid peroxidation consistent with ferroptosis
INTRODUCTION: Cerebral microbleeds (MB) are associated with sporadic Alzheimer's Disease (AD) and Down Syndrome with AD (DSAD). Higher MB iron may cause iron mediated lipid peroxidation. We hypothesize that amyloid deposition is linked to MB iron and that amyloid precursor protein (APP) triplication increases iron load and lipid peroxidation. METHODS: Prefrontal cortex and cerebellum of cognitively normal (CTL), AD and DSAD ApoE3,3 carriers were examined for proteins that mediated iron metabolism, antioxidant response, and amyloid processing in lipid rafts. RESULTS: Iron was 2-fold higher in DSAD than CTL and AD. Iron storage proteins and lipid peroxidation were increased in prefrontal cortex, but not in the cerebellum. The glutathione synthesis protein GCLM was decreased by 50% in both AD and DSAD. Activity of lipid raft GPx4, responsible for membrane repair, was decreased by at least 30% in AD and DSAD. DISCUSSION: DSAD shows greater lipid peroxidation than AD consistent with greater MBs and iron load.