bioRxiv Subject Collection: Neuroscience's Journal

Influenza A virus infection during pregnancy increases transfer of maternal bloodborne molecules to fetal tissues
Influenza A virus (IAV) infection during pregnancy is linked to heightened risk for neurodevelopmental disorders (NDDs) in the offspring. The precise pathophysiological mechanism(s) underling this association remains an active topic of research. We propose that maternal immune activation (MIA) triggered by IAV infection can disrupt selective permeability at the maternal-fetal interface, leading to increased transfer of blood-derived molecules into the fetal compartment. Some of these molecules might be responsible for the initiation of inflammatory cascades implicated in NDD etiology. Using a murine model of seasonal IAV infection during pregnancy, we examined placental and fetal brain barrier properties following maternal IAV challenge. Our findings demonstrate an enhanced transplacental transfer of fluorescently labeled tracers from maternal circulation to key neurodevelopmental regions, including the subventricular zone (SVZ) and choroid plexus (ChP) of fetal brains. This effect was most pronounced in fetuses from dams exposed to the highest dose of IAV. Notably, a similar pattern was observed for accumulation of the bloodborne neuroinflammatory molecule fibrinogen in these same brain regions, which was further amplified in response to the highest IAV dose. Moreover, fibrinogen accumulation was positively correlated with Iba1+ cell immunofluorescence, suggesting a potential interaction between fibrinogen and Iba1+ cells. Collectively, these findings suggest that IAV-induced MIA enhances transplacental transfer of blood-derived molecules into fetal tissues, potentially activating proinflammatory pathways in Iba1+ cells.

The mGluR5 Agonist, CHPG, Enhances Numbers of Differentiated Human Oligodendrocytes
Previous studies on adult mice indicate that the mGluR5 agonist 2-chloro-5-hydroxyphenyl glycine (CHPG), reduces cuprizone-elicited losses in myelin. This effect is partly mediated by CHPG binding to mGluR5 receptors on reactive astrocytes, triggering the release of brain derived neurotrophic factor (BDNF), which results in an increase in myelin, and alleviates behavioral deficits. However, it remains unclear whether CHPG has similar beneficial effects on human cells. To address this issue, we examined effects of CHPG on human cells using both human induced pluripotent stem cell (hiPSC)-derived oligodendrocytes and primary human fetal brain cells. Treatment of hiPSCs (30M, 5 days) or primary cells (30M, 3 days) with CHPG increases the percent of MBP+O4+ mature oligodendrocytes relative to total O4+cells, without affecting survival. When effects of CHPG were evaluated on proliferating OPCs, effects on proliferation are observed. In contrast, when CHPG was evaluated in young oligodendrocytes, effects on proliferation were gone, suggesting that in this population CHPG is influencing differentiation. Interestingly, in contrast to observations in mice, mGluR5 expression in humans is localized on PDGFR+ oligodendrocyte precursor cells (OPCs) and O4+ immature oligodendrocytes, but not astrocytes. Moreover, using purified human OPC cultures, we show a direct effect of CHPG in enhanced differentiation. To identify potential cellular targets of CHPG in the adult human brain, we analyzed postmortem tissue from individuals with multiple sclerosis (MS) and healthy controls. In contrast to the hiPSCs or fetal cells, demyelinated white matter from MS patients showed elevated mGluR5 mRNA expression in astrocytes. Taken together, our findings suggest that CHPG enhances the differentiation of human OPCs during development through a mechanism distinct from that observed in adult cuprizone-treated mice. Moreover, astrocytes in MS pathology upregulate mGluR5, suggesting they may become responsive to CHPG under disease conditions.

Transplantation of GABAergic Interneuron Progenitors Restores Cortical Circuit Function in an Alzheimer's Disease Mouse Model
In addition to dementia, Alzheimer's patients suffer from sleep impairments and aberrations in sleep-dependent brain rhythms. Deficits in inhibitory GABAergic interneuron function disrupt one of those rhythms, slow oscillation in particular, and actively contribute to Alzheimer's progression. We tested the degree to which transplantation of healthy donor interneuron progenitors would restore slow oscillation in young APP mice. We harvested medial ganglionic eminence (MGE) progenitors from mouse embryos and transplanted them into host APP mutant cortices. 3D light-sheet and structured illumination microscopy revealed that transplanted MGE progenitors survived and matured into healthy interneurons. In vivo multiphoton calcium imaging and voltage-sensitive dye imaging showed functional integration and slow oscillation rescue in absence or presence of optogenetic stimulation. Our work provides proof-of-concept evidence that stem cell therapy may serve as a viable strategy to rescue functional impairments in cortical circuits of APP mice and potentially those of Alzheimer's patients.

From Morphology to Computation: How Synaptic Organization Shapes Place Fields in CA1 Pyramidal Neurons
The synaptic mechanisms driving feature selectivity in specific neuron types remains a fundamental and unresolved challenge in neuroscience. In hippocampal CA1 pyramidal neurons (PNs), the development of place selectivity, manifested as place fields, is believed to result from dendritic integration of spatially distributed inputs combined with behavioral time scale plasticity (BTSP). BTSP involves dendritic spikes that temporally regulate synaptic potentiation and depotentiation. However, the role of excitatory (E) and inhibitory (I) synaptic distributions in the emergence of place specificity in CA1 PNs remains unclear, due to the lack of detailed synaptic reconstructions in vivo. Here, we present full synaptic reconstructions from individual CA1 PNs in the mouse hippocampus, revealing that these neurons receive approximately 10,000-15,000 E synapses and 900-1,400 I synapses. Computational modeling of biologically relevant E and I synaptic distributions shows that spatial tuning is preserved with co-tuned, spatially clustered E synapses, but disrupted when E distributions are randomized. Moreover, synapse clustering has a different contribution to spatial tuning in apical vs. basal domains. Our results reveal a complex and finely-tuned interplay between presynaptic input patterns and the spatial organization of their postsynaptic targets in dictating neuronal output in CA1 PNs.

Encoding of speech modes and loudness in ventral precentral gyrus
The ability to vary the mode and loudness of speech is an important part of the expressive range of human vocal communication. However, the encoding of these behaviors in the ventral precentral gyrus (vPCG) has not been studied at the resolution of neuronal firing rates. We investigated this in two participants who had intracortical microelectrode arrays implanted in their vPCG as part of a speech neuroprosthesis clinical trial. Neuronal firing rates modulated strongly in vPCG as a function of attempted mimed, whispered, normal or loud speech. At the neural ensemble level, mode/loudness and phonemic content were encoded in distinct neural subspaces. Attempted mode/loudness could be decoded from vPCG with an accuracy of 94% and 89% for two participants respectively, and corresponding neural preparatory activity could be detected hundreds of milliseconds before speech onset. We then developed a closed-loop loudness decoder that achieved 94% online accuracy in modulating a brain-to-text speech neuroprosthesis output based on attempted loudness. These findings demonstrate the feasibility of decoding mode and loudness from vPCG, paving the way for speech neuroprostheses capable of synthesizing more expressive speech.

Making new connections: An fNIRS machine learning classification study of neural synchrony in the default mode network
Successfully making connections with others is crucial to navigating the social world and general well-being, yet little is known about connection formation and its neurocognitive underpinnings. Increasingly, neuroscientists use interpersonal "neural synchrony" within the default mode network (DMN) to measure when two or more people subjectively experience something in similar ways. DMN synchrony as "seeing eye-to-eye" is typically observed when multiple people are passively observing the same stimulus. In this study, we tested whether the same DMN synchrony as "seeing eye-to-eye" pattern holds during social interactions. We conducted a between-subject naturalistic experiment with 70 pairs of strangers engaged in either shallow or deep conversations while brain activity was measured with functional near infrared spectroscopy (fNIRS). Stranger dyads successfully formed connections, as indicated by composite connection scores. Replicating Kardas et al. (2021), those in the deep conversation condition felt more connected than those in the shallow conversation condition. DMN neural synchrony significantly predicted self-reported connection, with synchrony in the DMN subregions of medial prefrontal cortex (mPFC) and right temporoparietal junction (TPJ) each correlating significantly with connection. Using machine learning classification, we distinguished high- versus low-connection dyads based on DMN neural synchrony and the perceived depth of conversation with 64.5% accuracy across 1,000 iterations. This effect was primarily carried by right TPJ, which alone classified connection strength at 62.6% accuracy. We consider implications related to the growing loneliness crisis and the importance of understanding how social connections can be formed and fostered in an era of increased social isolation.

Modelling Audio-Visual Reaction Time with Recurrent Mean-Field Networks
Understanding how the brain integrates multisensory information during detection and decision-making remains an active area of research. While many inferences have been drawn about behavioural outcomes, key questions persist regarding both the nature of environmental cues and the internal mechanisms of integration. These complexities make multisensory integration particularly well suited to investigate through mathematical modelling. In this study, we present three models of audio-visual integration within a biologically motivated mean-field recurrent framework. These models extend a non-linear system of differential equations originally developed for unisensory decision-making. The OR and SUM models represent opposing ends of the integration spectrum: the former simulates independent unisensory processing using a winner-take-all (WTA) strategy, while the latter implements a linear summation model for full integration. A third model, the REPEAT Model, incorporates switch and repeat costs observed in multisensory tasks. We simulate 121 participants with varying unisensory evidence accumulation rates, capturing behavioural diversity from modality dominance to balanced integration. Model outputs (reaction time and accuracy) were compared with empirical results from audio-visual detection tasks. We further fit the outputs to a drift diffusion model, allowing comparison between simulated and theoretically optimal multisensory drift rates. The OR and SUM Models reproduced established unisensory response patterns. Drift diffusion analysis revealed suboptimal integration in the OR Model and optimal integration in the SUM Model. However, the SUM Model also produced supra-optimal responses under certain conditions, inconsistent with behavioural data. The REPEAT Model successfully captured the role of priming in sensory repetition effects, distinguishing it from true multisensory integration. Overall, these models highlight how biologically grounded mathematical frameworks can shed light on the mechanisms underlying multisensory integration, particularly the nuanced contributions of modality repetition and integration efficiency.

Four-dimensional neural space for moral inference
Intuitive moral inference enables us to evaluate moral situations and judge their rightness or wrongness. Although Moral Foundations Theory provides a framework for understanding moral inference, its underlying neural basis remains unclear. To capture spontaneous neural activity during moral inference, participants were instructed to watch a film rich in moral content without making explicit judgments while undergoing fMRI scanning. Independent participants evaluated the moment-to-moment presence of twenty moral dimensions in the film. Correlation and consensus cluster analyses revealed four independent main moral dimensions: virtue, vice, hierarchy, and rebellion. While each dimension exhibited unique neural activation patterns, the temporoparietal junction and inferior parietal lobe were activated across all types of moral inference. These findings establish the low-dimensional nature for the neural basis of intuitive moral inference in everyday settings.

Dexmedetomidine produces more sleep-like brain activity compared to propofol
Introduction. Dexmedetomidine is a selective 2-adrenergic agonist used as an anesthesia adjunct to produce a state of sleep-like sedation. However, how brain activity compares quantitatively during dexmedetomidine anesthesia to that during natural sleep, and thus just how "sleep-like" dexmedetomidine anesthesia is, remains unclear. Previously, we showed that the general anesthetic propofol is associated with changes in connectivity and cortical network structure comparable to those observed during sleep. Here, we compare the effects on brain activity of dexmedetomidine, propofol, and sleep quantitatively using intracranial encephalographic (iEEG) recordings in human research participants. Methods. iEEG recordings were obtained in 34 epilepsy patients being evaluated for potential seizure resection surgery. Band power and functional connectivity (alpha weighted phase lag index, gamma envelope correlations) and network entropy were measured in recordings during task-free ("resting state") periods just prior to surgery during anesthesia with either dexmedetomidine or propofol, and during overnight sleep. Anesthesia stage (wake, sedated, unresponsive) was determined using the Observer's Assessment of Arousal and Sedation. Sleep was staged using standard polysomnography. Results. As expected, significant differences in delta power were observed during dexmedetomidine and propofol as well as during sleep. However, the magnitude of changes in delta power were smaller and regionally heterogeneous for propofol compared to dexmedetomidine and sleep. Functional connectivity changes were comparable between dexmedetomidine, propofol, and natural sleep. Significant changes in network entropy were observed for dexmedetomidine, propofol, and sleep, but changes were larger for propofol compared to dexmedetomidine and sleep. Quantitative comparisons between changes in delta power and network entropy suggest that unresponsiveness under dexmedetomidine produces a similar brain state to that observed during N2 sleep. Conclusions. While delta power, functional connectivity, and network entropy all showed changes during propofol, dexmedetomidine, and sleep, the magnitudes of these changes suggest that dexmedetomidine is more similar than propofol to sleep, specifically to N2 sleep.

Characterising Structural Brain Connectivity of Patients with First Episode of Psychosis
BACKGROUND AND HYPOTHESIS: Schizophrenia is associated with widespread neuroanatomical abnormalities affecting both grey matter and white matter (WM). Early symptoms are often linked to dysfunctions in the frontal cortex and the temporal lobe. This study aims to clarify WM alterations in early-stage psychosis and elucidate the role of structural connectivity (SC) in its pathophysiology. STUDY DESIGN: We analysed SC derived from diffusion MRI in 127 patients experiencing their first episode of schizophrenia (FES group), compared with healthy controls. Focusing on the fronto-parietal-temporal network, we examined SC across three hierarchical levels: network, node, and connection. SC metrics were compared between groups using 3-factor ANCOVA, accounting for relevant covariates. We also investigated associations between SC metrics and core positive symptoms using non-parametric correlations. RESULTS: The FES group showed significantly reduced average SC strength and global efficiency within the fronto-parietal-temporal network. At the nodal level, SC strength was significantly lower in the left inferior and middle temporal gyri (L.ITG, L.MTG), and in the right inferior parietal gyrus (R.IPG) and temporal pole (R.TP). No significant group differences emerged at the connection level. Notably, SC strength in the R.IPG was negatively correlated with Conceptual Disorganisation scores. CONCLUSIONS: Our findings reveal global and regional SC disruptions in early psychosis, particularly in areas supporting cognitive, language, and executive functions. The observed association between R.IPG connectivity and Conceptual Disorganisation supports the link between disrupted SC and formal thought disorder, reinforcing the role of impaired structural integration in early psychosis.

Prevalence and modulation of rat off-track head-scanning on linear tracks: possible implications for representational and dynamical properties of hippocampal place cells
(Re)mapping of different environments by hippocampal place cells is thought to reflect incidental learning. Rat head scanning is a spontaneous and presumed investigatory behavior that can trigger the onset of firing locations in place cells. This behavior was studied on (quasi-)circular tracks, and it was speculated that off-track head scans might have been overlooked or inadvertently discouraged in studies employing more common apparatus. To better understand the general prevalence and significance of off-track scanning, we investigated it in rats running laps on linear tracks in rooms featuring visual landmarks. Rats scanned along the entire length of the track, even in highly familiar conditions and when they were rewarded only at the two ends of the track (albeit less than rats rewarded throughout the track), demonstrating that co-localized rewards are not necessary for the occurrence of this behavior. Scanning rate increased markedly in a novel room and then declined steeply during each daily session in this room over 3 days. Partial daily boosts transiently counteracted this decline, producing a seesaw profile that is reminiscent of previous observations on rat rearing or place cell plasticity. Moreover, the remapping that place cells are known to undergo in similar context changes could conceivably be facilitated by the putative surge of new place fields induced by increased scanning. Hence, investigatory behaviors could be causally involved in the representational and dynamic properties of hippocampal representations. Addressing these possibilities could help uncover the learning processes governing the incidental creation and update of a cognitive map.

Locomotion-induced neural activity independent of auditory feedback in the mouse inferior colliculus
Accumulating evidence indicates that the auditory pathway integrates movement-related signals with auditory input, yet the precise sources and mechanisms of this integration across various processing levels are incompletely understood. The inferior colliculus (IC), a major midbrain hub in the auditory pathway, shows widespread modulation of neural activity during locomotion, indicating that auditory neurons at this level are sensitive to ongoing movement. However, in hearing animals, it has been challenging to dissociate auditory feedback from other motor-related signals. In this study, to isolate non-auditory contributions, we recorded IC neural activity during locomotion in deafened mice, thereby eliminating all auditory feedback through both air and bone conduction. Even in the absence of auditory input, IC neurons exhibited robust, bidirectional modulation during locomotion. Timing analysis using electromyography revealed both predictive and feedback components relative to locomotion onset. Furthermore, the timing and direction of modulation varied considerably across different locomotion bouts, suggesting convergence of multiple non-auditory inputs. These findings demonstrate that non-auditory, movement-related signals significantly shape auditory midbrain activity through both predictive and feedback mechanisms.

Reduced susceptibility to experimentally-induced complex visual hallucinations with age
Visual hallucinations occur across many clinical conditions, but can also be induced experimentally in healthy individuals, using high-frequency flicker (Ganzflicker) and sensory deprivation (Ganzfeld). It is unclear how hallucinatory proneness changes across the lifespan, with prior questionnaire-based studies showing mixed results. As factors such as multi-sensory acuity loss and relatively increased reliance on prior knowledge may increase as we age, and these are considered risk factors for hallucination proneness, we hypothesised that reported decreases in hallucinations might reflect stigma-related underreporting. We therefore sought to measure hallucination proneness in 44 healthy adults spanning the adult lifespan (younger age group; n=22; age 19-39 years, mean: 27.2, SD: 5.5; older age group n=22; age 59-79 years, mean: 68.0, SD: 5.8), quantifying the tendency to experience complex and simple hallucinations in an experimental environment designed to elicit hallucinations. We find that reports of complex hallucinations (those representing objects, scenes, etc) are lower in older adults than in younger adults, both in real time and retrospectively. None of our measured cognitive or sensory measures (visual acuity, contrast sensitivity, perceptual reorganisation, imagery vividness, memory inhibition, and suggestibility) mediate this relationship. We conclude that reduced complex hallucination proneness appears normative in ageing, and that experiencing hallucinations in older individuals may signal underlying pathology.

Motor impairment and adaptation in a novel non-human primate model of internal capsule infarct
Loss of distal hand and finger control is among the most disabling consequences of stroke. Functional outcomes are typically worse when infarcts involve subcortical white matter tracts, particularly the internal capsule, yet most preclinical stroke models target cortical regions. To address this gap, we developed a non-human primate model of internal capsule infarct using stereotactically guided endothelin-1 injections to disrupt descending fibers from the primary motor cortex hand area. Serial structural and diffusion MRI, along with histology, confirmed subcortical infarcts centered on the targeted white matter region with no apparent cortical involvement. Motor function was assessed pre- and post-infarct using a joystick-based center-out task (proximal forelimb control) and a Kluver board task (distal forelimb control). Animals exhibited variable impairments in proximal function and consistent post-infarct deficits in distal function, including reduced contralesional hand use, longer retrieval time, and increased in-well digit flexions. One animal showed mild post-infarct impairment and the smallest lesion, highlighting that this model reflects inter-individual differences in infarct size and functional outcome as seen in human subcortical stroke. In contrast, the other two animals developed a compensatory wrist-extended posture on the Kluver board task by 4 weeks post-infarct, which stabilized the hand and enabled improved digit flexion. Incorporating this behavioral adaptation into statistical models improved prediction of motor performance. The observed adaptation may have drawn on spared corticospinal output pathways, allowing animals to re-engage pre-existing motor routines to perform the retrieval. While future studies may benefit from ethologically relevant tasks to further elucidate such adaptations, findings from this study recapitulate key features of human subcortical stroke, including persistent distal motor deficits and emergence of adaptive motor strategies. By combining precise lesioning, longitudinal imaging, and detailed behavioral analysis, this model provides a translationally oriented platform for studying white matter stroke mechanisms and evaluating interventions that promote functional recovery.

Movement sonification during haptic exploration shifts emotional outcome without altering texture perception
Adding movement sonification to haptic exploration can change the perceptual outcome of a textured surface through multisensory processing. We hypothesized that auditory-evoked emotions would influence the appraisal of textured surfaces, with corresponding changes reflected in cortical excitability. Participants actively rubbed two different textured surfaces (slippery and rough) either without movement sonification, or with pleasant or disagreeable movement sonification. We found that sounds, whether agreeable or disagreeable, did not change the texture appraisal. However, the less pleasant surface was associated with a stronger negative hedonic valence, particularly when paired with disagreeable movement sonification. Time frequency analyses of EEG activities revealed a significant reduction in beta-band power [15-25 Hz] within the source-estimated sensorimotor and superior posterior parietal cortices when contrasting both pleasant and unpleasant sound with the silent touch. This suggests that the primary somatosensory cortices together with the superior parietal regions participated in the audio-tactile binding, with both pleasant and unpleasant sounds. In addition, we observed a significant increase in beta-band power in medial visual areas, specifically when disagreeable movement sonification was paired with tactile exploration. This may reflect a disengagement of visual cortical processing, potentially amplifying auditory-driven emotional responses and intensifying the perceived unpleasantness of the explored surfaces.

Basal forebrain volume is associated with cortical amyloid burden in cognitively unimpaired older adults at varying genetic risk for Alzheimers disease
Background: The primary cholinergic input to the cerebral cortex arises from the nucleus basalis of Meynert (nbM), a group of magnocellular neurons clustered within the posterior basal forebrain cholinergic system (BFCS). Postmortem and in vivo neuroimaging studies have demonstrated significant neuronal loss and BFCS atrophy, most prominently in the nbM, in both mild cognitive impairment and dementia due to Alzheimers disease (AD). However, less is known surrounding the relationship between accumulating Alzheimers pathology, BFCS atrophy, and cognition during early preclinical stages of AD. Methods: The current study investigates the relationship between sub-structural BFCS volume and cortical amyloid burden in cognitively unimpaired middle-aged individuals at varying genetic risk for AD. Cognitively unimpaired participants aged 50-65 with a first-degree family history for AD were genetically screened to select three groups: APOE genotype e4e4 (n=15), e3e4 (n=15), and e3e3 (n=15), matched for age and sex. Participants underwent imaging with [11C]PiB PET and structural 3T MRI. Distribution volumes ratios (DVR) with a whole cerebellum reference region were calculated for [11C]PiB PET analyses. BFCS sub-structural volumes were obtained from regions of interest generated from the SPM8 Anatomy Toolbox (Ch1-3, Ch4). Results: BFCS amyloid burden was highest among APOE e4e4 homozygotes (Ch1-3, F(2, 42)=3.26, P=0.048; Ch4, F(2, 42)=3.82, P= 0.03). Ch4(nbM), but not Ch1-3 volume, was found to be inversely associated with global amyloid burden (Pearson r=-0.40, P=0.007). Exploratory analyses in groups stratified by amyloid positivity demonstrated reduced Ch4 volume (P=0.032) and significant inverse associations between Ch4 volume and amyloid burden (Pearson r = -0.70, P=0.02) in amyloid+ participants. Medial temporal lobe (MTL) volumes were neither significantly different between amyloid+ vs. amyloid- participants nor were they associated with global amyloid burden in either amyloid+ participants, amyloid- participants, or the pooled sample. Conclusions: We observed nbM (Ch4), but not MTL volume, to be significantly inversely associated with cortical amyloid burden in cognitively unimpaired, amyloid+, older adults at varying genetic risk for AD. These findings provide further in vivo evidence suggesting BFCS (specifically nbM) atrophy may precede medial temporal atrophy in the preclinical stage of AD and that nbM atrophy is an early structural correlate of AD pathogenesis.

A Movement-Independent Signature of Urgency During Human Perceptual Decision Making
How does the brain adjust its decision processes to ensure timely decision completion? Computational modelling and electrophysiological investigations have pointed to dynamic 'urgency' processes that serve to progressively reduce the quantity of evidence required to reach choice commitment as time elapses. To date, such urgency dynamics have been observed exclusively in neural signals that accumulate evidence for a specific motor plan. Across three complementary experiments, we show that a classic ERP component, the Contingent Negative Variation (CNV), also traces dynamic urgency but exhibits unique properties not observed in effector-selective signals. Firstly, it provides a representation of urgency alone, growing only as a function of time and not evidence strength. Secondly, when choice reports must be withheld until a response cue, the CNV peaks and decays long before response execution, mirroring the early termination dynamics of a motor-independent evidence accumulation signal. These properties suggest that the brain may use urgency signals not only to expedite motor planning but also to hasten cognitive deliberation. These data demonstrate that urgency processes operate in a variety of perceptual choice scenarios and that they can be monitored in a model-independent manner via non-invasive brain signals.

Abnormal synaptic proteomes, impaired neural ensembles, and defective behaviors in autism mouse models are ameliorated by dietary intervention with nutrient mixtures
Autism spectrum disorders (ASD) are a group of heterogeneous, behaviorally defined neurodevelopmental conditions influenced by both genetic and environmental factors. Here, we show that nutrients--an important environmental factor--can modulate synaptic proteomes, reconfigure neural ensembles, and improve social behaviors in ASD mouse genetic models. We analyzed Tbr1+/- mice, a well-established model of ASD, using proteomic approaches and in vivo calcium imaging. Synaptic and metabolic proteomes were found to be sensitive to Tbr1 haploinsufficiency. Our results also revealed that Tbr1 haploinsufficiency promotes hyperactivation and hyperconnectivity of basolateral amygdala (BLA) neurons, enhancing the activity correlation between individual neurons and their corresponding ensembles. Zinc, branched-chain amino acids (BCAA), and serine--all nutrients known to regulate synapse formation and activity--were then combined into supplement cocktails and administered to Tbr1+/- mice. This treatment altered synaptic and metabolic proteomes and normalized the activity and connectivity of the BLA in Tbr1+/- mice during social interactions. We further show that although a low dose of individual nutrients did not alter social behaviors, treatment with supplement cocktails containing low-dose individual nutrients improved social behaviors and associative memory of Tbr1+/- mice, implying a synergistic effect of combining low-dose zinc, BCAA, and serine. Moreover, the supplement cocktails also improved social behaviors in Nf1+/- and Cttnbp2+/M120I mice, two additional ASD mouse models. Thus, our findings reveal aberrant neural connectivity in the BLA of Tbr1+/- mice and indicate that dietary supplementation with zinc, BCAA, and/or serine offers a safe and accessible approach to mitigate neural connectivity and social behaviors across multiple ASD models.

Pyruvate kinase activates SARM1 to exacerbate axonal degeneration in diabetic peripheral neuropathy
Diabetic peripheral neuropathy (DPN) is a prevalent and disabling complication of diabetes, characterized by progressive axonal degeneration. However, the molecular link between hyperglycemia and axon injury remains unclear. Here, we identify pyruvate kinase M (PKM) as a direct metabolic activator of the NADase SARM1 under high-glucose conditions. Proteomic and biochemical analyses reveal that PKM binds the TIR domain of SARM1 via its C-terminal region, allosterically enhancing NADase activity independently of PKM's glycolytic role. In dorsal root ganglion (DRG) neurons, hyperglycemia strengthens the PKM-SARM1 interaction, driving NAD+ depletion, axonal fragmentation, and sensory dysfunction. Genetic depletion of PKM protects against streptozotocin-induced neuropathy, preserving nerve fiber density, restoring NAD+ levels, and alleviating mechanical allodynia. Most notably, we developed Pep-SP1, a competitive inhibitory peptide derived from residues 645-655 of the SARM1 TIR domain, which selectively disrupts the PKM-SARM1 interaction without impairing PKM metabolism or SARM1 catalytic activity. Systemic delivery of Pep-SP1 attenuates axonal degeneration and improves sensory outcomes in diabetic mice. By targeting a disease-potentiating interface, we expand therapeutic strategies beyond catalytic and allosteric inhibition, offering a mechanistically distinct avenue for axon protection with broad relevance to metabolic and neurodegenerative disorders.

Opposing effects of H2A.Z on memory, transcription and pathology in male and female Alzheimer's disease mice and patients
Alzheimer's disease (AD) is a devastating neurodegenerative disease that disproportionately impacts women, but underlying mechanisms for sex-divergent outcomes are unknown. Here, we show that the histone variant H2A.Z is a novel sex-specific regulator of AD in human patients and AD model mice. Specifically, H2A.Z binding in chromatin declines in female and increases in male AD patients, indicating opposite patterns of AD-related H2A.Z dysregulation in each sex. These sex differences were recapitulated in the 5xFAD model of AD, in which females accumulated H2A.Z at early disease stages and lost H2A.Z as the disease progressed, suggesting that H2A.Z occupancy shifts with advancing disease. Males showed no change in H2A.Z binding in early disease, but exhibited increased binding as disease progressed, albeit to a lesser extent than females. Consistent with sex-specific H2A.Z dysregulation, H2A.Z depletion produced sex-specific changes in gene expression, whereby H2A.Z was more repressive in female than male mice and in 5xFAD than in WT males, suggesting that H2A.Z's role in transcription is altered with disease state. Moreover, H2A.Z depletion improved memory and AD pathology in females, while impairing memory and worsening pathology in male mice. Together, these data suggest that H2A.Z is protective in males and detrimental in females with AD, with key implications for sex-specific therapeutic targeting of chromatin factors.

Overexpression of DnaJ chaperones in ameliorating toxicities associated with FUS and TDP-43
Amyotrophic Lateral Sclerosis (ALS) is an adult-onset neurodegenerative disease. It primarily affects the motor neurons, leading to muscle weakness and eventual death of patients. Various factors, such as genetics, environment, age, etc, are involved in the etiopathogenesis of ALS. As ALS is a highly challenging and complex disease that involves various pathogeneses linked with progressive motor neuron degeneration, it is difficult to have a single therapeutic target against this disease. ALS mutants of TDP-43 and FUS are showing slow growth as well as protein aggregation in the cytoplasm in yeast. Our study involves cloning of 38 Drosophila DnaJ domain chaperones and overexpressing them in a yeast ALS model. After the interaction of mutants TDP-43 and FUS with the DnaJ domain chaperones, they were categorized into suppressors and enhancers. The major hits on our screen were CG7872, Hsc70-4, and Mrj, which rescued TDP-43 toxicity by reducing the protein aggregation and slow growth in yeast cells. In the FUS, slow growth and protein aggregation is reduced with the chaperones CG32641 and CG6693, resulting in a lowering of the FUS toxicity. On the other hand, chaperones CG2911, CG2790, and CG8476 in the presence of TDP-43 overexpression, grow more slowly with increasing punctae in yeast cells. These chaperones increase the toxicity of TDP-43. Similarly, in FUS, Hsc20, CG7130, CG2911, and JdpC also showed a slow growth phenotype and increased protein aggregation in yeast cells. These chaperones enhance the toxicity of FUS. This screening will enhance our understanding of ALS, and the chaperones identified in this study can serve as neuroprotective agents for ALS.

Protective role of Cannabidiol against nicotine pouch-induced seizure aggravation and alterations in brain glymphatic biomarkers.
Nicotine pouches are increasingly popular as a smokeless alternative to tobacco, yet their long-term neurological effects remain poorly understood. In this preclinical study, we investigated the time-dependent impact of oral nicotine pouch exposure on seizure susceptibility, glymphatic function, and neuroinflammation in mice, and evaluated the therapeutic potential of inhaled cannabidiol (CBD). Using the Racine scale, we found that acute nicotine exposure transiently reduced seizure severity, while chronic exposure significantly exacerbated seizures and impaired glymphatic integrity, as evidenced by downregulation of aquaporin-4 (AQP4). Chronic nicotine also elevated circulating levels of HMGB1 and IL-6, indicating sustained systemic inflammation. Notably, inhaled CBD reversed these pathological changes, reducing seizure severity, restoring AQP4 expression, and normalizing inflammatory markers. Molecular analyses further revealed upregulation of BDNF and c-FOS with chronic nicotine exposure, which was also mitigated by CBD. In conclusion, these findings suggest that while nicotine pouches may confer short-term neurophysiological modulation, chronic use poses significant risks for seizure vulnerability and glymphatic dysfunction. Inhaled CBD demonstrates strong neuroprotective potential and may serve as a promising therapeutic approach for individuals exposed to prolonged nicotine use.

Effects of Natural Lithium and Lithium Isotopes on Voltage Gated Sodium Channel Activity in SH-SY5Y and IPSC Derived Cortical Neurons
Although lithium (Li) is a widely used treatment for bipolar disorder, its exact mechanisms of action remain elusive. Research has shown that the two stable Li isotopes, which differ in their mass and nuclear spin, can induce distinct effects in both in vivo and in vitro studies. Since sodium (Na+) channels are the primary pathway for Li+ entry into cells, we examined how Li+ affects the current of Na+ channels using whole-cell patch-clamp techniques on SH-SY5Y neuroblastoma cells and human iPSC-derived cortical neurons. Our findings indicate that mammalian Na+ channels in both neuronal models studied here display no selectivity between Na+ and Li+, unlike previously reported bacterial Na+ channels. We observed differences between the two neuronal models in three measured parameters (Vhalf, Gmax, z). We saw no statistically significant differences between any ions in SHSY-5Y cells, but small differences in the half-maximum activation potential (Vhalf) between Na+ and 6Li+ and between 7Li+ and 6Li+ were found in iPSC-derived cortical neurons. Although Na+ channels are widely expressed and important in neuronal function, the very small differences observed in this work suggest that Li+ regulation through Na+ channels is likely not the primary mechanism underlying Li+ isotope differentiation.

A Minimal Physiological Model of Perceptual Suppression and Breakthrough in Visual Rivalry
Visual rivalry paradigms provide a powerful tool for probing the mechanisms of visual awareness and perceptual suppression. While the dynamics and determinants of perceptual switches in visual rivalry have been extensively studied and modeled, recent advances in experimental design - particularly those that quantify the depth and variability of perceptual suppression - have outpaced the development of computational models. Here we extend an existing dynamical model of binocular rivalry to encompass two novel experimental paradigms: a threshold detection variant of binocular rivalry, and tracking continuous flash suppression. Together, these tasks provide complementary measures of the dynamics and magnitude of perceptual suppression. Through numerical simulations, we demonstrate that a single mechanism, competitive (hysteretic) inhibition between slowly adapting monocular populations, can account for the suppression depth findings across both paradigms. This unified model offers a foundation for the development of a quantitative theory of perceptual suppression in visual rivalry.

Recovery of retinal terminal fields after traumatic brain injury: evidence of collateral sprouting and sexual dimorphism
The central nervous system is characterized by its limited regenerative potential, yet striking examples of functional recovery after injury in animal models and humans highlight its capacity for repair. Little is known about repair of pathways/circuits after traumatic brain injury (TBI), which results in disruption of connectivity. Here we utilize a mouse model of diffuse traumatic axonal injury (Impact-acceleration TBI) in order to explore, for the first time, the evolution of structural and functional changes in the terminal fields of the injured visual system. Retinal ganglion cell (RGC) axons and synapses were genetically labeled via AAV transduction, while anterograde and transsynaptic tracers were used to mark terminals and postsynaptic cells. Functional connectivity and visual integrity were assessed by monitoring c-Fos expression following light stimulation and visual evoked potentials (VEPs). Our findings demonstrate that, although TAI results in approximately a 50% loss of RGC axons and terminals, surviving RGCs generate collateral sprouting, a form of compensatory branching of surviving axons, that restores terminal density to pre-injury levels. Transsynaptic tracing and c-Fos mapping confirmed the reestablishment of connectivity, which was also associated with significant improvements in visual function as measured by pVEPs. Interestingly, the recovery process exhibited sexual dimorphism, with female mice showing delayed or incomplete repair. Moreover, collateral sprouting proceeded normally in Sarm1 knockout mice, evidence of some independence from Wallerian degeneration. Our findings show that collateral sprouting may be an important mechanism of circuit repair in TAI independent of Wallerian degeneration and may represent a promising target for therapeutic interventions.

Lysosomal stress induces amyloid-β aggregate release and reactive transformation in human astrocytes
Astrocytes are essential for brain homeostasis and are involved in amyloid-{beta} (A{beta}) clearance, but whether they can produce and release A{beta} aggregates remains unclear. Using human iPSC-derived astrocytes, we show that astrocytes cell autonomously generate small, diffusible A{beta} aggregates under baseline conditions. By combining ultrasensitive single-molecule imaging (DNA-PAINT) and immunoassays, we detect intracellular aggregates and their release into the media. Notably, lysosomal membrane damage induced by L-leucyl-L-leucine methyl ester (LLOMe) significantly increases A{beta} aggregate secretion without altering their size or morphology. Transcriptomic analysis and cytokine profiling reveal that lysosomal stress triggers a reactive astrocyte phenotype marked by upregulation of inflammatory genes and secreted cytokines. These findings suggest that astrocytes are not merely passive A{beta} scavengers but can actively contribute to extracellular A{beta} accumulation under lysosomal stress. Our study highlights astrocytes as active players in Alzheimer's disease pathology.

EEG reveals how space acts as a late heuristic of time
To compensate for its sensory intangibility, humans often rely on spatial metaphors, gestures, and visual tools to represent the passage of time. These spatial tools, i.e. heuristics, range from everyday practices, such as directional hand gestures to indicate past or future events, to more abstract scientific conceptualizations such as the curving of space-time in the theory of relativity. Despite this widespread spatialization of time, it remains unclear to what extent space is an inherent component of the neural representation of time and its role in monitoring temporal durations. Here, we combine EEG-behavioral methods and neural network models of optimal decision-making to show that space is a late compensatory mechanism of time representation recruited when faster and non-spatial timekeeping mechanisms are suboptimally engaged. EEG analyses reveal a cascade-like process: spatial engagement in timekeeping follows the insufficient non-spatial encoding of time intervals, leading to delayed decisions on their length and slower response selection. Computational modelling further indicates that trial-by-trial fluctuations in the spatialization of time are explained by stochastic variations in the activity of the dopaminergic/noradrenergic (DA/NE) system and its interaction with the anterior cingulate cortex. These findings provide the first clear evidence of when, why, and how the brain recruits spatial mechanisms in the service of temporal processing and demonstrate that non-spatial and spatial timekeeping systems can be dissociated at both behavioural and electrophysiological levels.

Rab2 and Arl8/BORC control retrograde axonal transport of dense core vesicles via Syd/dJIP3/4 and RUFY dynein adaptors
Neuropeptide-containing dense core vesicles (DCVs) are generated in the neuronal cell body and circulate throughout the axonal arbor to supply distal release sites. This circulation depends on the anterograde kinesin-1 and kinesin-3 motors and the retrograde dynein-dynactin motor. While kinesin-3 is recruited to DCVs with the aid of the small GTPase Arl8, it is unclear how dynein and kinesin-1 are recruited and regulated. Here we show that DCV motility in Drosophila (fruit flies) depends on the dynein and kinesin-1 adaptor Sunday Driver/dJIP3/4(Syd) and the novel dynein adaptor RUFY. Syd and RUFY bind each other; moreover, Syd binds the DCV-located GTPase Rab2 that controls retrograde DCV transport, and RUFY binds Arl8. Disruption of Rab2, Syd, RUFY, dynein, and the Arl8 activator BORC all produce a similar DCV axonal transport phenotype characterized by axonal accumulation of immobile DCVs and a selective reduction in retrograde DCV flux. Our data suggest a model where dynein is recruited and activated by a complex of Syd and RUFY, which is anchored to DCVs by a Rab2- and Arl8-dependent mechanism. Lastly, we show that loss of Rab2 results in missorting of the DCV membrane proteins VMAT and Synaptotagmin-, similar to the reported effect of Rab2 deletion on the sorting of synaptic vesicle and active zone proteins. However, disruption of Syd, RUFY or dynein does not phenocopy the Rab2 specific VMAT sorting defect, suggesting that Rab2 employs separate effectors in DCV biogenesis and motility.

Peptides alleviate cognitive impairment by inhibiting and disassembling amyloid-beta aggregates in Alzheimer disease
Alzheimer disease (AD) is a devasting neurodegenerative disorder characterized by beta-amyloid formation, further exacerbated by RIPK1/RIPK3 necrosome-induced programmed necrosis (necroptosis). We previously showed that the RIPK1/RIPK3 necrosome forms a functional amyloid complex using its RIP homotypic interaction motifs (RHIMs). Here, we discovered that the core RIPK1/RIPK3 necrosome shares strikingly structural similarity to the C-terminal region of beta-amyloid (Ab-42), and the RHIM-derived tetrapeptides (IQIG or VQVG) directly inhibit Ab aggregation, disassemble preformed Ab fibrils (PFFs), and reduce RIPK1 polymerization. Also, the peptides exhibit effective membrane permeability and could reduce Ab-40 or Ab-42-induced neural death and TNFa-induced necroptosis in SH-SY5Y cells. IQIG and VQVG injected by ICV increase learning and memory abilities by reducing Ab plaques and hyperphosphorylated tau in the cortex and hippocampus of APP/PS1 double-transgenic mice. Mechanistically, the peptides directly interact with A{beta} to block Ab aggregation and alleviate microglia-mediated neuroinflammation. Strikingly, single-cell RNA sequencing revealed that the peptides-treated AD transgenic mice restored neuronal homeostasis with increased GABAergic neurons and decreased glutamatergic neurons. Furthermore, total cell-cell interaction strength increased while the AD risk gene Apoe expression decreased in the specific oligodendrocyte subtype of peptides-treated AD mice. Thus, our findings revealed that the peptides could improve cognition and memory capabilities and serve as promising structural templates for potential drugs against AD.

Atypical antipsychotics alter microglial functions via astrocyte-derived extracellular vesicles
A limited understanding of the underlying molecular mechanisms of atypical antipsychotics has hindered efforts to develop the next generation of treatments for schizophrenia. In particular, there has been little investigation of how medications like clozapine and olanzapine modulate human non-neuronal cells, including astrocytes and microglia. Recent postmortem and serum-based studies suggest that schizophrenia etiology involves dysregulated cellular communication through extracellular vesicles (EVs). Astrocytes are a major source of these EVs and are strongly implicated in the etiology of schizophrenia by convergent data from human postmortem, brain imaging, RNA-sequencing, and genome-wide association studies. We hypothesized that clozapine and olanzapine can affect microglia biology indirectly via astrocytic secretion of EVs. We used in vitro cellular models with primary human astrocytes and PBMC-derived microglial-like cells to investigate the downstream impact of isolated astrocyte-derived EVs (ADEVs) on microglial phenotypes relevant to schizophrenia, including microglial phagocytosis, motility, and morphology. To model microglia-mediated synaptic pruning in vitro, we utilized image-based quantification of microglia engulfment of isolated human synaptosomes. We found that treatment with ADEVs reduced microglial synaptosome phagocytosis in a dose-dependent manner. This reduction was reversed upon addition of ADEVs isolated from astrocytes treated with norclozapine or olanzapine. ADEVs isolated from clozapine-treated astrocytes increased microglial motility, indicating that clozapine alters microglial surveillance activity without affecting phagocytosis through these ADEVs. Together, these results suggest that atypical antipsychotics have distinct and indirect impact on microglia biology mediated by ADEVs. These results highlight a potentially critical role for ADEVs in regulating glial cell communication and suggest they may be promising therapeutic targets for next-generation antipsychotic development.