bioRxiv Subject Collection: Neuroscience's Journal

Structural Covariance Network Properties Predictive of Early Adolescent Alcohol Initiation
Importance: Early alcohol initiation (before age 15) is associated with adverse outcomes. Understanding mechanisms behind early alcohol initiation is essential for informing prevention efforts. Objective: To examine whether structural covariance network properties at ages 9-10 years predict early alcohol initiation. Design: Case-control, population-based study design. Setting: Data from the Adolescent Brain Cognitive Development study were used. Baseline structural brain imaging data (ages 9-10) were used for generation and comparison of structural covariance networks. Data from baseline to 4-year follow-up ([≤]age 15) assessments were used to determine alcohol initiation. Participants: Participants were excluded if they reported consuming a full drink of alcohol at baseline, or did not meet imaging inclusion criteria. Controls were excluded if they had not yet been assessed or were missing substance use data at 4-year follow-up. In total, 3,878 participants met study criteria, of which 182 participants initiated alcohol. Structural covariance network properties were compared between the full sample and a 1:1 propensity-matched sample based on age, sex, race, ethnicity, religion, parental education, prenatal alcohol exposure, and baseline alcohol sipping. Main Outcomes and Measures: Structural covariance networks were estimated using regional cortical thickness and volume measurements. Measures of network segregation (modularity, clustering coefficient), integration (characteristic path length, global efficiency), and resilience (degree assortativity) were compared between groups. Early alcohol initiation was defined as consuming a full drink between baseline and 4-year follow-up. Results: Alcohol initiators (n=182, median[IQR] age, 10.3[9.9-10.8]; 101 female[55.5%]) demonstrated lower network segregation (modularity: area-under-the-curve[AUC] difference[95%CI]=-0.017[-0.017,-0.007], p=0.030; clustering coefficient: AUC[95%CI]=-0.026[-0.027,-0.012], p=0.0495) and higher network integration (characteristic path length: AUC[95%CI]=-0.106[-0.099,-0.046], p=0.020; global efficiency: AUC[95%CI]=0.011[0.005,0.011], p=0.010), compared to non-initiators (n=3,696, median[IQR] age, 9.9[9.4-10.4]; 1750 female[47.4%]) when controlling for age, sex, and mean cortical thickness. Within the matched sample, only differences in network integration were preserved (characteristic path length: AUC[95%CI]=-0.044[-0.032,0.035], p=0.010; global efficiency: AUC[95%CI]=0.003[-0.003,0.003], p=0.040). There were no differences between full or matched samples when comparing cortical volume structural covariance networks. Conclusions and Relevance: Differences in cortical thickness structural covariance network properties at ages 9-10 predicted alcohol initiation before age 15. These findings suggest cortical thickness network topology may reflect a neuroanatomical risk marker for early alcohol initiation.

Inhibiting glucocorticoid receptors enhances adult spinal cord neural stem cell activity and improves outcomes in spinal cord injury
The internal microenvironment plays a critical role in the proliferation and differentiation of endogenous neural stem/progenitor cells (NSPCs). A big change in the spinal cord injury (SCI) microenvironment is the elevated level of glucocorticoids. In this study, we examined the impact of glucocorticoids on endogenous NSPCs in the adult mouse spinal cord. Our findings reveal that adult spinal cord NSPCs express glucocorticoid receptors, but not mineralocorticoid receptors. Glucocorticoids were found to significantly inhibit the proliferation and neurosphere formation of NSPCs via activation of glucocorticoid receptors, and they also impaired their differentiation. Importantly, the glucocorticoid receptor inhibitor CORT125281 was shown to enhance motor function in a traumatic SCI model in mice. Treatment with CORT125281 increased the number of NSPCs at the injury site in vivo. Flow cytometry and RNA sequencing analyses indicated that glucocorticoids induce NSPC arrest in the G1/G0 phase through the p53 signaling pathway. Glucocorticoids increased the expression of cell-cycle regulatory genes p15, p16, p18, and p27 in adult spinal cord NSPCs. In summary, our data suggest that glucocorticoids elevation following SCI suppresses the proliferation of endogenous NSPCs via glucocorticoid receptor activation. Targeting glucocorticoid receptors with specific inhibitors may represent a novel therapeutic strategy to promote recovery after spinal cord injury.

Factor Analysis of Multimodal MRI, Biofluid and Vascular Health Biomarkers Reveals Latent Constructs of Brain Health
Individual imaging and fluid biomarkers provide insights into specific components of brain health, but integrated multimodal approaches are necessary to capture the complex, interrelated biological systems that contribute to brain homeostasis and neurodegenerative disease. Using data from the Brain and Cognitive Health (BACH) cohort study (N=127; mean age=67 years, 68% women), we performed an exploratory factor analysis to identify latent constructs of brain health. We included multimodal neurovascular imaging markers, brain atrophy metrics, plasma Alzheimers disease (AD) biomarkers and cardiovascular risk factors. Five constructs emerged: Brain & Vascular Health (greater hippocampal volume, basal ganglia enlarged perivascular spaces [ePVS], cerebral blood flow and HDL cholesterol; lower ventricle volume and BMI); Structural Integrity (greater cortical thickness, fractional anisotropy and basal ganglia ePVS); Fluid Transport (greater white matter ePVS and Free Water); AD Biomarkers (higher phosphorylated tau [pTau]181 and pTau217; lower amyloid-beta 42/40 ratio); and Neuronal Injury (higher glial fibrillary acidic protein and neurofilament light chain). All constructs were associated with age ({beta}=-0.70-0.39, p[≤].014), except for Fluid Transport (p>.05). Brain & Vascular Health and Structural Integrity (partial r=.305, p<.001), and AD Biomarkers and Neuronal Injury (partial r=.248, p=.005) were positively correlated. Only Brain & Vascular Health was associated with global cognition ({beta}=0.27, SE=0.13, p=.043). These findings provide a data-driven framework for examining distinct constructs underlying vascular health, fluid regulation and neurodegenerative pathology. We demonstrate the utility of using multiple biomarkers to probe these biological systems, paving the way for future research to explore how these systems change across diverse neurodegenerative conditions.

APOE4-induced patterned behavioral decline and neurodegeneration requires endogenous tau in a C. elegans model of Alzheimers disease
Alzheimers disease (AD) causes a characteristic spatiotemporal pattern of neurodegeneration, resulting in the loss of associated faculties such as cognition. The factors which account for this pattern of degeneration are unclear, as AD risk genes are numerous and often broadly expressed. Previously, we generated a model of AD using the nematode Caenorhabditis elegans in which the AD risk variant of apolipoprotein E, APOE4, is pan-neuronally expressed. We showed that HSN class motor neurons degenerate in early adult. Here, we expand on our past work by performing behavioral analyses to deduce the effect of APOE4 on the function of distinct neuronal circuits. We found evidence that APOE4 induces dysfunction of other neurons; this spatiotemporal pattern of degeneration roughly correlates with endogenous levels of PTL-1, the C. elegans homolog of human MAPT also known as tau. Moreover, deletion of ptl-1 suppressed defects in multiple behaviors, suggesting broad protective effects across the nervous system including the HSN neurons. Lastly, we show that PTL-1 in the touch receptor neurons, where PTL-1 is most abundant, is required cell nonautonomously for degeneration of the HSN neurons. Our results suggest that C. elegans may provide a useful in vivo system to study how endogenous Tau acts downstream of APOE4 to cause progressive, patterned neurodegeneration.

Cholinergic neuron circadian clock mediates RNA-binding protein function and contributes to ALS disease phenotypes
Circadian clocks are encoded by a transcription-translation feedback loop that aligns physiological processes with the solar cycle. Previous work linking the circadian clock to the regulation of RNA-binding proteins (RBPs) and alternative splicing provides a foundation for the vital examination of their mechanistic connections in the context of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease characterized by disrupted RBP function. Here, we reveal enrichment of genes associated with ALS and other neurodegenerative diseases in the spinal cord cholinergic neuron rhythmic transcriptome. We demonstrate that there is circadian regulation of ALS-linked RBPs and rhythmic alternative splicing of genes involved in intracellular transport (Aftph and Mvb12a), microtubule cytoskeleton organization (Limch1 and Drc3), and synaptic function (Sipa1l2) in this neuronal sub-type. Further, we show that the cholinergic neuron clock regulates sporadic ALS-associated changes in cytoskeleton and neuromuscular junction synapse gene expression. Finally, we report that cell-type-specific Bmal1-deletion (i) increases sciatic nerve axon degeneration, (ii) drives alternative splicing of genes encoding ALS-linked RBPs (Matr3 and Srsf7), and (iii) drives alternative splicing of genes associated with microtubule transport and postsynaptic organization. Our results establish a role for the cholinergic neuron clock in RBP function and ALS disease phenotypes.

Histology to MRI registration quality of ex vivo human brain blocks fixed with solutions used in anatomy laboratories
Introduction. Post-mortem brain tissue is obtained from brain banks that provide small tissue samples, while gross anatomy laboratories could become a source of complete brains for neuroscientists. These are preserved with solutions whose chemical composition differs from the classic neutral-buffered formalin (NBF) used in brain banks, such as a saturated-salt-solution (SSS) or an alcohol-formaldehyde solution (AFS) that preserve antigenicity of the main brain cell populations. Since histology remains the gold standard in neuroscientific research, while MRI is the most common imaging modality, MRI-histology registration quality needs to be assessed to ensure the suitability using brains fixed with innovative solutions for research procedures. Hence, our goal was to compare the registration quality of human brains fixed with NBF, SSS and AFS, as well as the histological characteristics that could affect the registration. Methods. We used 12 human brain blocks of 3x3x3 cm3 fixed in our anatomy laboratory using SSS (N=4), AFS (N=4), or NBF (N=4). The blocks were scanned using a 7Tesla Bruker animal MRI scanner with a T2-TurboRARE sequence at 0.13x0.13x0.5mm3. Blocks were then cut into 40m thick sections (parallel to the 0.13x0.13 plane) using a vibratome. Sections were stained with histochemistry (HC) (Cresyl violet, Prussian blue, Luxol fast blue, H&E, and Bielschowsky) and immunohistochemistry (IHC) of the 4 main cell populations: neurons (NeuN), astrocytes (GFAP), microglia (Iba1) and myelin (PLP) either with or without an antigen retrieval (AR) protocol. Stained sections were imaged using a slide scanner microscope and segmented with masks using Display, and the sections were manually registered to the T2-TurboRare images using landmarks in Register (MincToolKit). Results. More landmarks were needed to achieve proper alignment of the histology to MRI images for the SSS-fixed blocks, due to the lower GM-WM contrast in these brains. However, there was no significant difference in the staining intensity of the histology sections of blocks fixed with the three solutions, while SSS-fixed blocks showed a lower percentage of overlap between the good histology quality masks and the MRI masks. This resulted in a sufficient registration quality of all blocks, although more challenging when fixed with SSS. Conclusion. We have developed histology, MRI and registration protocols that are of good quality in brain blocks fixed with solutions used in gross anatomy laboratories. These results are promising for neuroscientists interested in using full brains from anatomy laboratories, either using MRI, histology or registration of both modalities to study normal aging and neurodegenerative conditions.

Acute E2/P4 loss compromises the biology and function of neurogenic niches during a vulnerable female aging period
Effects of aging on neural stem progenitor cells (NSPCs) have been studied in males, but less is known in females. Here we comparatively assess female NSPC biology, both in the subventricular zone and hippocampal dentate gyrus niches, across different ages of F344 rats (2, 6, 9 and 14 months). The rats were ovariectomized (OVX) or remained Intact at each of the aging stages, to assess the role of the female sex hormones, estradiol (E2) and progesterone (P4). Results show that while age-dependent decays become prominent at 14 months, ovariectomy-induced E2/P4 loss markedly reduces neurogenesis and associated behavioral function, earlier, at 9 months of age. Coinciding with this pattern of neurogenic decline, we also detect adaptive changes in estrogen and progesterone receptor expression, antioxidant expression, and brain E2/P4 levels. Fundamentally, these results reveal specific female time-periods, when the brain is sensitive to age and E2/P4 loss, potentially setting-up for disease susceptibility.

Vessels hiding in plain sight: quantifying brain vascular morphology in anatomical MR images using deep learning
Non-invasive assessment of brain blood vessels with magnetic resonance (MR) imaging provides important information about brain health and aging. Time-of- flight MR angiography (TOF-MRA) in particular is commonly used to assess the morphology of blood vessels, but acquisition of MRA is time-consuming and is not as commonly employed in research studies or in the clinic as the more standard T1- or T2-weighted MR contrasts (T1w/T2w). To enable quantification of brain blood vessel morphology in T1w/T2w images, we trained a neural network model, anat2vessels, on a dataset with paired MR/MRA. The model provides accurate segmentations as assessed in cross-validation on ground truth images, particularly in cases where T2w images are used. In addition, correlation between features that are extracted from model-based vessel segmentations and from ground truth account for as much as 78% of the variance in these features. We further evaluated the model in another dataset that does not include MRA and found that anat2vessels-based vessel morphology features contain information about aging that is not captured by cortical thickness features that are routinely extracted from T1w/T2w images. Moreover, we found that vessel morphology features are associated with individual variability in blood pressure and cognitive abilities. Taken together these results suggest that anat2vessels could be fruitfully applied to a range of existing and new datasets to assess the role of brain blood vessels in aging and brain health. The model is provided as open-source software in https://github.com/nrdg/anat2vessels/.

Idebenone Enhances the Early Microglial Response to Traumatic Brain Injury and Mitigates Acute Gene Expression Changes to Ephrin-A and Dopamine Signaling Pathways
Traumatic Brain Injury (TBI) leads to persistent pro-inflammatory microglial activation implicated in neurodegeneration. Idebenone, a coenzyme Q10 analogue that interacts with both mitochondria and the tyrosine kinase adaptor SHC1, inhibits aspects of microglial activation in vitro. We used the NanoString Neuropathology panel to test the hypothesis that idebenone post-treatment mitigates TBI pathology-associated acute gene expression changes by moderating the pro-inflammatory microglial response to injury. Controlled cortical impact to adult male mice increased the microglial activation signature in peri-lesional cortex at 24 hours post-TBI. Unexpectedly, several microglial signature genes upregulated by TBI were further increased by post-injury idebenone administration. However, idebenone significantly attenuated TBI-mediated perturbations to gene expression associated with behavior, particularly in the gene ontology:biological process (GO:BP) pathways 'ephrin receptor signaling' and 'dopamine metabolic process.' Gene co-expression analysis correlated levels of microglial complement component 1q (C1q) and the neurotrophin receptor gene Ntrk1 to large (>3-fold) TBI-induced decreases in dopamine receptor genes Drd1 and Drd2 that were mitigated by idebenone treatment. Bioinformatics analysis identified SUZ12 as a candidate transcriptional regulator of idebenone-modified gene expression changes. Overall, results suggest that idebenone enhances TBI-induced microglial proliferation within the first 24 hours of TBI and identify Ephrin-A and dopamine signaling as novel idebenone targets.

Lifestyle, Early-life, and Genetic Health Risk Factors Underlying the Brain Age Gap: A Mega-Analysis Across 3,934 Individuals from the ENIGMA MDD Consortium
Background: Large-scale studies show that adults with major depressive disorder (MDD) generally have a higher imaging-predicted age relative to their chronological age (i.e., positive brain age gap) compared to controls, though considerable within-group variation exists. This study examines lifestyle, early-life, and genetic health risk factors contributing to the brain age gap. Identifying risk and resilience factors could help protect brain and mental health. Methods: Using an established model trained on FreeSurfer-derived brain regions (www.photon-ai.com/enigma_brainage), we generated brain age predictions for 1,846 controls and 2,088 individuals with MDD (aged 18-75) from 12 international cohorts. Polygenic risk scores (PRS) were calculated for major depression, C-reactive protein, and body mass index (BMI) using large-scale GWAS results. Linear mixed models were applied to assess lifestyle (BMI, smoking, education), early-life childhood trauma, and genetic (PRS) health risk associations with the brain age gap. Additionally, we evaluated the link between the brain age gap and peripheral biological age indicators (epigenetic clocks). Results: Higher brain age gaps were significantly associated with BMI ({beta}=0.01, PFDR=0.02) and smoking ({beta}=0.11, PFDR=0.02), while lower brain age gaps were linked to higher education ({beta}=-0.02, PFDR=0.02). Higher childhood trauma scores predicted a higher brain age gap ({beta}=0.04, P=0.01). Higher brain age gaps were positively associated with all PRS ({beta}s=0.04-0.16, PsFDR=0.02-0.03). There were no significant interactions between diagnosis and assessed factors on the brain age gap. In a multivariable model, only modifiable health factors (BMI, smoking, and education) remained uniquely associated with brain age gaps. Conclusions: Genetic liability for depression and related traits is linked to poorer brain health, but health behaviors potentially offer a key opportunity for intervention. This study underscores the importance of targeting modifiable lifestyle factors to mitigate poor brain health in depressed individuals, an approach perhaps under-recognized in clinical practice.

Sleep stage-specific effects of 0.75 Hz phase-synchronized rTMS and tACS on delta frequency activity during sleep
Slow oscillatory activity during non-rapid-eye-movement (NREM) sleep plays a crucial role in both physical health and cognitive functions. Enhancing slow oscillatory activity during sleep has the potential to benefit these domains, yet an optimal stimulation protocol has not been established. This study aimed to investigate whether repetitive transcranial magnetic stimulation (rTMS), synchronized with the trough phase of 0.75 Hz transcranial alternating current stimulation (tACS) can modulate EEG activity in the delta frequency range during sleep and enhance cognitive functions. Healthy adults participated in a within-subject, counterbalanced study design comparing real and sham stimulation conditions. Combined rTMS and tACS was applied over the bilateral prefrontal cortex before sleep. We evaluated (1) power spectral density and functional connectivity within the delta frequency range during resting state and sleep, (2) retention of declarative memory learned before sleep, and (3) sleep parameters including spindle activity, sleep stage ratios, sleep onset latency and sleep efficiency. The combined rTMS and tACS protocol significantly increased delta oscillatory activity during the N3 sleep stage compared to sham. Functional connectivity, as measured by global efficiency, was enhanced during the N2 sleep stage. However, the stimulation did not improve declarative memory retention, spindle activity or other sleep parameters. These findings demonstrate the potential of combined rTMS and tACS as a non-invasive method to enhance delta oscillatory activity during sleep. While the stimulation did not improve memory performance, its ability to modulate delta activity during sleep suggests potential clinical applications for addressing pathological alterations in slow wave activity during sleep.

Resting state periodic and aperiodic brain oscillations from birth to preschool years: Aperiodic maturity predicts developmental course
The non-invasive assessment of resting-state (RS) neural activity via electrophysiology provides information on brain function and brain health. Our understanding of RS neural activity in older children and adults is limited by our poor understanding of the maturation of RS activity (oscillatory and non-oscillatory) from infancy to preschool ages. The present study used MEG with source imaging and an adapted Dark Room eyes-open task to assess oscillatory and non-oscillatory RS activity. 107 typically developing children 2 to 68 months were enrolled. For the Dark-Room eyes-open task, each child alternated between viewing an Inscapes video without audio for 20s and then resting with their eyes open for 30s in total darkness. This was repeated for 6 cycles. Whole-brain RS activity maps were computed using Minimum Norm Estimates, with RS power spectra divided into estimates of periodic measures (dominant frequency and power) and aperiodic measures (the exponent - slope of the 1/f function; the offset - vertical displacement of the 1/f function). An infant dominant peak was observed more often in the Dark-Room (94% of children) than in the Video-On condition (83% of children). The Dark-Room condition elicited a 36% increase in dominant oscillation activity than the Video-On condition. The maturation of the parietal-occipital periodic dominant frequency increased non-linearly as a function of age. The maturation of aperiodic measures decreased nonlinearly as a function of age, with aperiodic measures as well as their maturation rate differing across the brain. Finally, more mature aperiodic values predicted better adaptive behaviors and daily living skills. Present findings demonstrate that (1) the use of an appropriate Dark-Room eyes-open task provides measures of young child RS periodic activity with excellent SNR, (2) an understanding of the development of infant RS activity is best achieved via obtaining measures in brain source space in order to detect regional differences in aperiodic activity, and (3) a more mature aperiodic value predicts higher developmental behavior scores.

LINKING MULTI-SCALE BRAIN CONNECTIVITY WITH VIGILANCE, WORKING MEMORY, AND BEHAVIOR IN ADOLESCENTS
This study examines how multi-scale intrinsic connectivity networks (ICNs) relate to cognitive and behavioral functions in adolescents, focusing on attention/vigilance, working memory, and behavioral regulation. Leveraging the NeuroMark 2.2 multi-scale ICN template obtained from over 100,000 subjects, we obtained multi-scale ICNs from baseline resting-state fMRI data from the ABCD Study. For this study, we are interested in "the fronto- thalamo-cerebellar (FTC) circuitry" and choose the subdomains of Neuromark 2.2 that cover it: Cerebellar (CB), Subcortical - Extended Thalamic (SC-ET), Higher Cognition - Insular Temporal (HC-IT), and Higher Cognition - Frontal (HC-FR), previously identified as relevant to cognitive and behavioral functions. Employing a multivariate approach combining principal component analysis (PCA) and canonical correlation analysis (CCA), we examined associations between these multi-scale ICNs and cognitive-behavioral outcomes. Our findings revealed significant associations, particularly for one of the estimated canonical components, linking multi-scale ICNs to cognitive and behavioral measures across both discovery and replication sets. This connectivity pattern may serve as a potential marker for attention, working memory, and behavioral regulation, offering new insights into a wide spectrum of neurodevelopmental disorders including Attention-Deficit/Hyperactivity Disorder (ADHD).

Neurochemical imaging reveals changes in dopamine dynamics with photoperiod in a seasonally social vole species
Studying dopamine signaling in non-model organisms is crucial for understanding the broad range of behaviors not represented in traditional model systems. However, exploring new species is often hindered by a scarcity of tools suitable for non-genetic models. In this work, we introduce near-infrared catecholamine nanosensors (nIRCats) to investigate dopamine dynamics in meadow voles, a rodent species that exhibits distinct changes in social behavior and neurobiology across photoperiods. We observe increased dopamine release and release site density in social voles under short photoperiods, suggesting adaptations linked to environmental changes. Moreover, pharmacological and extracellular manipulations demonstrate that social voles exhibit heightened responsiveness to dopamine-increasing interventions and resilience against suppressive conditions. These findings highlight a significant association between dopamine signaling and photoperiod-driven changes in social behavior and establish nIRCats as an effective tool for expanding our understanding of dopamine dynamics across non-model organisms.

Brain-derived synaptic vesicles have an intrinsic ability to sequester tubulin
The presence and function of microtubules within the synaptic bouton has long been under investigation. In recent years evidence has accumulated that connects the synaptic vesicle cluster to the local dynamics of microtubule ends. Nonetheless, one question remains open, namely whether the vesicles influence the availability of tubulin within the synaptic compartment. An analysis of previously published live imaging experiments indicates that tubulin is strongly enriched in the synaptic vesicle cluster. To analyze the vesicle-tubulin interaction directly, we isolated vesicles from the mouse brain and imaged them together with fluorescent tubulin in vitro. We found that soluble tubulin is collected by synaptic vesicles in physiological buffers, resulting in the formation of tubulin-rich regions (TRRs) on the respective vesicle clusters. We conclude that the synaptic vesicle cluster is indeed able to recruit soluble tubulin.

Atlas-independent brain connectome analysis at voxel-level granularity: graph convolutional networks for etiology classification in newborns
Early identification of altered brain networks in neonates at risk for neurodevelopmental impairments is critical for timely intervention and improving outcomes. This study explores the potential of graph convolutional networks (GCNs) applied to structural brain connectomes at the voxel level granularity to classify neonatal connectomes by their underlying etiology: 51 children with congenital heart disease (CHD), 100 children born very preterm (PB), and 43 children with spina bifida aperta (SBA). Leveraging the flexibility of voxel-level parcellation, we captured fine-grained connectomic differences that improved classification performance (F1 = 0.78) compared to both atlas-based methods (F1 = 0.62) and a multilayer perceptron baseline model (F1 = 0.69). This approach enables subject-specific parcellation without the need for predefined anatomical templates, facilitating the analysis of diverse brain morphologies and age ranges. Attribution analysis using integrated gradients provided interpretable insights into etiology-specific connectomic patterns, highlighting regions of potential neurodevelopmental importance, such as the Rolandic operculum, inferior parietal lobule, and inferior frontal gyrus. Lateralized attribution patterns in PB reflected known neurodevelopmental alterations, underscoring the value of interpretable graph learning for understanding etiology-specific connectomic features. This work represents an important step toward atlas-independent connectome analysis, offering a novel framework for studying diverse neonatal populations and advancing our understanding of early brain development.

Spatially Organized IGF1 mTOR Signaling Controls Human Forebrain Progenitor Fate Through Coordinated Transcriptional and Translational Programs
The specification and maintenance of human forebrain neural progenitor cells (NPCs) depend on both intrinsic gene networks and spatially localized niche signals, but the interplay between these cues remains incompletely understood. Here, we identify a spatially organized, paracrine IGF1 signaling architecture that regulates human FOXG1 positive NPCs through multilayered transcriptional and translational control. Using a pluripotent stem cell derived forebrain model, we show that FOXG1 positive NPCs express IGF1 receptors but lack endogenous IGF1, instead depending on neighboring epithelial-like domains that secrete IGF1. IGF1 promotes progenitor proliferation, clonal expansion, and vertical tissue growth by activating PI3K AKT mTOR and MEK ERK pathways. Ribosome profiling and 5-UTR reporter assays reveal that mTOR signaling selectively enhances translation of neurodevelopmental and biosynthetic transcripts including GSX1, a ventral fate determinant implicated in interneuron specification and autism. These findings uncover a human-specific regulatory mechanism in which spatially restricted IGF1 mTOR signaling integrates niche signals with translational output to support progenitor identity, biosynthetic capacity, and developmental resilience.

Predicting cochlear synaptopathy in mice with varying degrees of outer hair cell dysfunction using auditory evoked potentials
Human temporal bones suggest a steady decline of cochlear synapses with age and greater synapse loss in adults with a history of military or occupational noise exposure. However, there is currently no validated method of diagnosing this type of cochlear deafferentation in living humans. Animal models indicate that cochlear synaptopathy is associated with reduced auditory brainstem response (ABR) wave 1 amplitude and envelope following response (EFR) magnitude for a sinusoidally amplitude modulated (SAM) tone. However, translating the SAM EFR to humans is complicated because it is difficult to obtain this measurement in humans using the same modulation frequency that showed the strongest relationship with synaptopathy in mice (1000 Hz). Computational modeling suggests that EFR magnitude measured with a rectangular amplitude modulated (RAM) tone may be a more sensitive measure of synaptopathy than the SAM EFR. In addition, because synaptopathy likely co-occurs with outer hair cell dysfunction, a diagnostic assay for synaptopathy needs to be robust even when auditory thresholds are abnormal. This study compared the relative ability of the ABR, SAM EFR, and RAM EFR to predict synapse numbers in mice with a large range of auditory thresholds and degrees of synaptopathy. The results indicate that the RAM EFR modulated at 1000 Hz is the single best predictor of synapse number when there is a broad loss of synapses across frequency, while combining RAM EFR and ABR further improves synapse prediction. In contrast, focal synaptopathy is best predicted by ABR wave 1 amplitude.

BetaII-Spectrin Gaps and Patches Emerge from the Patterned Assembly of the Actin/Spectrin Membrane Skeleton in Human Motor Neuron Axons
The membrane-associated periodic skeleton (MPS), composed of F-actin and spectrin, is a cytoskeletal structure that supports axonal integrity and organization. Using high-resolution imaging, we characterized the spatial distribution and assembly dynamics of {beta}II-spectrin in human motor neuron (MN) axons derived from induced pluripotent stem cells (iPSCs). We discovered a striking gap-and-patch pattern in the medial axon, where sharply demarcated {beta}II-spectrin gaps alternate with patches containing a well-organized MPS. These gaps lack periodic F-actin and II-spectrin and do not reflect axonal degeneration or spectrin cleavage. The pattern increases with culture time and is acutely induced by the kinase inhibitor staurosporine. Notably, pharmacological inhibition of actin polymerization prevents patch formation, indicating a requirement for actin nucleation in MPS assembly. Our data supports a model in which spectrin incorporation into nascent MPS patches depletes neighboring regions, producing periodic interruptions. This study provides the first detailed nanoscale analysis of MPS organization in human MNs, offering new insights into cytoskeletal remodeling in axons and its potential relevance to neurodegenerative diseases such as amyotrophic lateral sclerosis. Key words: iPSCs, MPS, actin, spectrin, cytoskeleton, motor neurons, staurosporine.

Profiling metabotropic glutamate receptor 7 expression in Rett syndrome: consequences for pharmacotherapy
We have reported that levels of metabotropic glutamate receptor 7 (mGlu7) are dramatically decreased in brain samples from Rett syndrome patients carrying truncation mutations in the Methyl-CpG Binding Protein 2 (MECP2) gene. Additionally, we identified decreases in mGlu7 levels in Mecp2+/- female mice and demonstrated that administration of a positive allosteric modulator (PAM) with activity at mGlu7 corrected deficits in cognitive, social, and respiratory domains. Here, we expanded our studies to a larger cohort of RTT samples covering a range of mutations and evaluated expression of the three widely expressed group III mGlu receptors (mGlu4,7 and 8). We found significant decreases in mGlu7, but not mGlu4 or mGlu8, mRNA expression across this larger cohort; additionally, we identified a previously unknown and robust correlation in the expression of mGlu4 and mGlu8 in control individuals. Stratification of RTT patients into individuals with mutations that are clinically correlated with severe versus mild disease revealed statistically significant decreases in mGlu7 expression only in patients with mutations that induce more severe symptoms. We then administered the PAM VU0422288 to mice modeling the mild R306C mutation (Mecp2R306C/+) and found a significant reduction in apneas induced by VU0422888 administration despite no decreases in mGlu7 expression in the brainstem or cortex. These results provide the first evidence of potentially broad utility for mGlu7 PAMs in reducing apneas in RTT patients.

Hippocampal reactivation of planned trajectories is required for effective goal choice in an allocentric memory task
Abstract It still remains unclear how the brain replays stored neural information, and whether such replay merely reflects past experiences or also plans of future endeavours. Hippocampal activity provides a representation of the world around us and our movement and navigation within that world, but it is not known if and to what extent the chosen navigational reference frame can influence hippocampal representations during memory-based tasks, including those focused on future activity. Here, we develop and employ two naturalistic, carefully controlled variants of the everyday memory task to model the use of egocentric and allocentric coordinates in the same arena. By recording hippocampal neural activity through miniature microscopes in rats performing each of the two tasks, we uncover differences in the representation of space, and in the features of memory-based action planning. By also deploying optogenetic inactivation during navigational decision making, we find that hippocampal representations observed during the planning phase are necessary for solving the allocentric, but not the egocentric version of the task. Overall, our findings reveal a functional link between non-local hippocampal representations and allocentric navigation.

Neural Mechanisms Supporting Proactive Control
Recent prior work suggests a preferential relationship between working memory capacity (WMC) and proactive control, yet the neural mechanisms that support this relationship are still not well understood. We directly addressed this question by leveraging the Dual Mechanisms of Cognitive Control (DMCC) project, as it employed a fMRI neuroimaging design optimized to test for individual differences (sample N > 100), with task variants that independently assessed proactive and reactive control relative to baseline conditions. Behavioral analyses replicated prior work with the AX-CPT paradigm, in which a measure of target preparation based on contextual cues (the A-cue Bias index) was both reliably increased under task conditions encouraging proactive control and positively associated with WMC. Analyses of fMRI activity indicated that A-cue Bias was selectively linked to increased cue-related neural activity in left motor cortex (lMOT). Additionally, WMC was associated with increased cue-related activation in right dorsolateral prefrontal cortex (rDLPFC), even when statistically controlling for baseline and reactive conditions. The relationship between these two effects was supported by a latent path analysis, which suggested that the rDLPFC-lMOT circuit preferentially mediates the WMC-A-cue Bias relationship present under proactive task conditions. The results suggest this neural circuit may translate strategic task goals into active response preparation as a mechanism of proactive control. Individuals high in WMC may be better able to implement proactive task strategies when instructed via contextual cues. The sensitivity of the rDLPFC-lMOT circuit to individual differences suggest it as a potential target for cognitive enhancement.

Synaptic dynamics govern spatial integration in mouse visual cortex
Neurons in primary visual cortex are often suppressed by stimuli extending beyond their receptive fields. This surround suppression is proposed to reduce the redundancy of encoding large stimuli and support scene segmentation. We find that surround suppression decreases firing rates in mouse primary visual cortex by accelerating the decay of visually-evoked responses and reducing response duration. The rapid decay of visual responses at large sizes is enhanced by increased contrast, reduced by locomotion, and invariant to stimulus orientation, consistent with the engagement of a network mechanism. While fast-spiking interneurons have faster dynamics relative to neighboring pyramidal cells, the dynamics of somatostatin-expressing interneurons are delayed. At the subthreshold level, the rapid decay of visual responses with increasing size is due to a delayed removal of both synaptic excitation and inhibition below baseline levels following visual input. We propose that the delayed activation of somatostatin-expressing interneurons drives a network-wide suppression and accelerates the decay of the visual response. Thus, these data identify a key role for synaptic network dynamics in regulating both spatial and temporal integration in mouse visual cortex.

Psilocybin-induced modulation of visual salience processing
Psychedelic compounds significantly reshape conscious perception, yet the implications of these alterations for complex visual-guided behaviors remain poorly understood. We investigated how psilocybin modulates visual salience processing during natural scene perception. Twenty-three participants completed eye-tracking tasks under self-blinded low and high doses of psilocybin, in a naturalistic design with experimental conditions unknown to participants and researchers. Subjects viewed natural scenes while their gaze patterns were recorded and analyzed in relation to normative computational saliency maps generated using a deep learning model of visual attention. Results revealed increased fixation on salient image regions and reduced inter-fixation distance under the high-dose condition, suggesting heightened sensitivity to visual salience and more localized gaze behavior. The Shannon entropy of fixations on high-saliency regions indicated a more exploratory and less predictable visual scanning of the images. Complementary EEG recordings showed broadband spectral power reductions and increased Lempel-Ziv complexity, with delta power negatively correlating with salience metrics. These findings suggest psilocybin enhances bottom-up attentional control while weakening top-down modulation, consistent with theoretical models positing facilitated bottom-up information flow under the acute effect of psychedelics.

Decoding hypnotic consciousness: neural and experiential insights into induced and ideomotor suggestions
Hypnotic induction and ideomotor suggestions provide a powerful framework to investigate how verbal influence dynamically reshapes conscious experience, cognition, and motor control. We employed a multimodal approach combining high-density EEG, respiratory and behavioral monitoring, and first-person reports across three conditions: baseline resting state, progressive hypnotic induction (Light and Deep phases), and an ideomotor challenge comparing a hypnotically suggested arm catalepsy to a voluntary simulation. EEG results revealed that light hypnosis was associated with early parieto-occipital alpha suppression and increased theta-band activity. As hypnosis deepened, frontoparietal connectivity increased while parasympathetic activation declined, challenging the view of hypnosis as a passive, low-arousal state and instead pointing to active top-down reorganization of large-scale brain networks. During the ideomotor phase, participants exhibited distinct patterns of behavioral responsiveness, classified as tremblers and non-tremblers, despite reporting comparable disruptions in the sense of agency; phenomenological analyses corroborated these distinctions by uncovering divergent experiential strategies. Tremblers showed increased frontoparietal gamma activity and reduced delta connectivity, suggesting heightened sensorimotor integration and greater executive monitoring under motor conflict. Together, these findings show that hypnosis engages dynamic top-down processes that reconfigure both neural connectivity and subjective experience, supporting predictive coding accounts of agency disruption and highlighting the value of neurophenomenological methods for advancing consciousness science and informing clinical applications.

Retinal image motion distracts visual motion memory even when generated by eye movement
Interference between visual short-term memory (VSTM) and task-irrelevant sensory distractors is a well-documented phenomenon across a wide range of visual features, which is believed to stem from neural interactions between mnemonic and sensory processing. An overlooked question in the ongoing debate is whether this VSTM distraction is linked to the original sensory information or the ultimate perceptual experience. Here we addressed this issue by leveraging the perceptual invariance during ocular tracking of an object (i.e., smooth pursuit), where retinal image motion induced by smooth pursuit is encoded in early visual areas involved in motion processing, including the middle temporal (MT) and the medial superior temporal (MST) areas, but is perceptually suppressed. Our results showed that retinal image motion during the VSTM maintenance (delay period) attracted the memorized motion speed, consistent with previous studies. Importantly, the impact was comparable whether the retinal image motion was due to physical displacement of objects in world coordinates or to apparent motion induced by smooth pursuit without actual motion in world coordinates. In fact, observers' responses in the VSTM task were partially predicted by retinal image motion during the delay period by a cross-condition classifier, where the distraction effect induced by the smooth pursuit-induced apparent motion was replicable using a classifier trained on data from the condition with the world-coordinate motion, and vice versa. These findings provide behavioral evidence that sensory inputs can distract VSTM without conscious perception and also suggest that the VSTM system shares neural substrates with sensory processing, but not with perception.

Chiral shift toward D-serine reflects intrathecal inflammation in multiple sclerosis and counteracts motor impairment in a murine model
Multiple sclerosis (MS) is characterized by chronic inflammatory demyelination involving complex interplay between the central nervous and immune systems. Neuroinflammation triggers cellular reorganization requiring L-serine for sustained syntheses of membrane lipids and nucleic acids, whereas it causes aberrant glutamatergic neurotransmission involving D-serine. However, significance of serine metabolism in MS pathology remains unexplored. Here we show that serine chiral homeostasis is disrupted in MS and endogenous D-serine prevents motor deficits caused by inflammatory demyelination. We found in a large cohort study that patients with MS exhibit elevated D-serine levels and the D-/total serine ratio in the cerebrospinal fluid at diagnosis. Steric deviation toward D-serine accords with emergence of the intrathecal inflammatory marker oligoclonal bands, and correlates negatively with proinflammatory cytokines. An in vivo animal model of MS, genetically engineered to exhibit distinct metabolic states of D-serine, revealed that endogenous D-serine synthesis mitigates the progression of motor deficits and suppresses proinflammatory and vascular endothelial pathogenic signaling. Moreover, pre-symptomatic oral supplementation with D-serine, but not L-serine, enhances production of extracellular matrices, preserves integrity of the blood brain barrier, attenuates demyelination, and improves motor function. Contrary to the previously recognized neurotoxic nature of D-serine, our findings reveal an unrecognized significance of D-serine metabolism in MS and a protective function of D-serine against neuroinflammation involving disruption of the blood brain barrier, which may present an untapped therapeutic target in MS.

Adolescent cannabinoid vapour exposure sex-dependently alters the relationship between vulnerability traits and ethanol self-administration and modifies naltrexone actions on ethanol intake in rats
Background: Cannabis use during adolescence is common and may predispose individuals to substance use disorders. Animal studies have explored the gateway hypothesis, but data on ethanol consumption are limited. This study aimed to investigate the potential link between adolescent cannabis exposure and ethanol self-administration, as well as the relationship between predisposing behavioural traits and ethanol consumption. Methods: Adolescent rats were exposed to vapourised {Delta}9-tetrahydrocannabinol (THC) alone or with cannabidiol (CBD) at different ratios, or to a vehicle, from postnatal day (PND) 28 to 44, every other day. Behavioural assessments, including novelty and saccharin preference, goal-tracking, elevated plus maze, and ethanol self-administration (fixed and progressive ratio, punished seeking), were conducted from PND 70. Naltrexone was administered to assess its effects on ethanol intake. Results: Cannabinoid exposure did not significantly affect behavioural traits or ethanol self-administration. However, sex differences emerged, with females showing a more vulnerable pattern of ethanol consumption and seeking. In THC-exposed males, a negative correlation was observed between sucrose preference and compulsive ethanol seeking, which was absent in vehicle-exposed males. In females, THC exposure disrupted the correlation between novelty preference and ethanol intake and was associated with a negative correlation between goal-tracking and compulsive seeking. Naltrexone was most effective in reducing ethanol intake in THC-exposed rats. Conclusions: Adolescent cannabinoid exposure has limited effects on overall alcohol risk but may alter the psychological framework of alcohol-related behaviours and increase naltrexone potency. The observed sex differences highlight the need for personalised interventions.

Unmasking Convergent Oxycodone Seeking and Consumption Driving Augmented Intake during Extended Access to Oral Operant Self-Administration
Individual vulnerability to opioid intake escalation is a critical but poorly understood aspect of addiction. Using genetically diverse inbred rat strains, we investigated operant oral oxycodone self-administration, identifying Augmenter phenotypes that dramatically increased consumption during extended (16h vs. 4h) access, a vulnerability not predicted by standard motivation tests. A key innovation was applying lick microstructure analysis (LMA) to operationally distinguish 'consumption' from seeking lick clusters within the inter-reward interval. During extended access, Augmenters of both sexes exhibited a striking surge in the frequency of both consumption and seeking clusters (p<0.0001), driving their escalated intake. Notably, female Augmenters also showed larger seeking cluster sizes (p=0.006), suggesting enhanced reward value specifically linked to seeking behavior. In contrast, interlick interval (a palatability measure) did not differentiate phenotypes. This LMA-based approach reveals that an increased drive to seek out additional oxycodone, rather than altered hedonic impact alone, underlies the augmentation of opioid intake, offering a nuanced rodent model of heightened vulnerability and a powerful tool to dissect reward dynamics.