Journal of Neuroscience Research

Background: Persistent neurological and cognitive symptoms following SARS-CoV-2 infection point to long-term alterations in brain structure and function. The thalamus, orbitofrontal cortex, and limbic networks are particularly susceptible to inflammatory and neurovascular stressors. However, the relationship between cortical, white-matter, and thalamocortical alterations in post-COVID syndrome remains unclear. Methods: 76 COVID-19 recovered participants (CRPs) and 51 healthy controls (HCs) underwent multimodal MRI comprising T1-weighted structural, diffusion, and resting-state functional acquisitions. Grey-matter morphology was assessed using voxel-based morphometry (VBM), white-matter microstructure using tract-based spatial statistics (TBSS), and thalamocortical functional connectivity (TC-FC) using seed-based analyses from major thalamic nuclei. Results were evaluated both across the groups (HC vs. CRP) and after stratifying CRPs by hospitalisation status (HC vs. Non-hospitalized patients (NHPs) vs. Hospitalized patients (HPs)). Results: No group-level grey-matter differences were observed between HCs and CRPs; however, HPs showed localized volume loss in the orbitofrontal and frontal-pole cortices (pFWE < 0.05). TBSS revealed widespread microstructural abnormalities, including reduced fractional anisotropy and mean diffusivity across association and commissural tracts (pcorr < 0.05), with regional increases in mode of anisotropy indicating selective loss of crossing fibres (pcorr < 0.05). Resting-state analyses revealed increased TC-FC from the mediodorsal thalamic nucleus to anterior cingulate, parietal, and occipital cortices (pcorr < 0.05), while differences in pulvinar and ventrolateral nuclei were not significant (pcorr > 0.05). Conclusions: Our findings indicate that COVID-19 recovery is associated with enduring alterations in fronto-limbic and thalamo-cortical circuits, most prominently in individuals with severe infection. Convergent structural and functional changes involving the orbitofrontal cortex and mediodorsal thalamus suggest network-specific reorganisation that may underpin persistent cognitive and affective symptoms of post-COVID syndrome.

2)BackgroundCircadian rhythm desynchrony (CD) occurs when there is a mismatch between the circadian clock and local time, such as shift work. Mouse models are commonly employed to study CD, but may have significant shortcomings such as environmental masking, a focus only on sleep physiology, and significant variability between study designs. ObjectiveThis study used in vivo telemetry for simultaneous, real-time monitoring of locomotor activity (LA), core body temperature (CBT), and brain activity (EEG) in freely moving C57BL/6J mice to assess CD effects. MethodsFour-month-old C57BL/6J mice (n=11) were surgically implanted with telemeters enabling simultaneous real-time recording of LA, CBT, EEG.: Mice were sequentially exposed to a control condition standard 12:12h light-dark cycle (T24) then 4, 8-day CD paradigms: 10:10 h short day (T20), social jet lag (SJL), repeated 6h phase advances (6A2), and a 3:3 h ultradian cycle (T6)For each paradigm, the final 48h of data (250 Hz) were analyzed. ResultsWe found clear differences in the severity of the effects of each CD paradigm on sleep and circadian fitness, where T20[~]T6>SJL>6A2. CBT revealed broader disruption, but EEG outputs proved the most sensitive indicators of internal desynchrony. ConclusionsEach CD paradigm produced a unique profile across behavioral, physiological, and neural domains. We have also identified Gamma CV as a novel, sensitive metric of CD. These results highlight the necessity of multimodal monitoring to accurately characterize the impact of ecologically relevant stressors on circadian and sleep physiology. Statement of SignificanceCircadian rhythm desynchrony (CD), driven by shift work, jet lag, and modern irregular light exposure, is a major health burden linked to metabolic, neurodegenerative, and neuropsychiatric diseases. However, standard methods for measuring CD in laboratory models often rely on simple locomotor activity, which can "mask" the true extent of internal circadian stress. In this study, we simultaneously monitored brain EEG activity, core body temperature, and motion across four distinct models of circadian stress. We discovered that locomotor activity is a deceptive indicator of health; while mice appeared to show no alterations under several stress paradigms, their brain waves and body temperatures revealed the underlying impact of CD. Specifically, we identified "Gamma CV" as a highly sensitive new brain-wave marker that detects early circuit instability even when behavior appears normal and sleep quantity is preserved. These findings provide a marker for identifying early neurological vulnerability to irregular light schedules, offering a potential bridge to understanding similar gamma brain-wave alterations seen in addiction, early-stage Alzheimers disease, and other disorders.

Abstract: BACKGROUND: Perivascular spaces (PVS), visible on brain MRI, contribute to the brain clearance system and are associated with age and neurodegenerative disorders. While lower volumes of PVS in the forebrains white matter and basal ganglia have been also demonstrated in preterm-born neonates, the long-term trajectory of PVS after premature birth remains unclear. This study tests for altered PVS volumes in very preterm/very low birthweight-born (VP/VLBW) adults compared to full-term controls and explores potential associations with cognitive performance. METHODS: PVS were assessed on T2-weighted MRI from 97 VP/VLBW and 89 full-term (FT) subjects at 26 years from the prospective, population-based Bavarian Longitudinal Study. PVS volume and count was based on automated nnU-Net-based segmentation. Regional PVS volumes were normalized by corresponding regional parenchyma volumes. Cognitive performance was assessed by the Wechsler Adult Intelligence Scale. MANCOVA was used for PVS group comparisons, Spearman rank correlations for testing PVS relationships with birth variables and cognitive scores. RESULTS: VP/VLBW-born adults showed significantly higher normalized PVS volumes in bilateral basal ganglia (p < 0.001, partial eta-squared = 0.096) and insula-related white matter (p = 0.001, partial eta-squared = 0.057). In the basal ganglia, higher PVS volumes were negatively correlated with gestational age (rho = -0.223, p = 0.030) and positively correlated with the Intensity of Neonatal Treatment Index (rho = 0.222, p = 0.030) in the VP/VLBW group. PVS volume was not associated with IQ scores. CONCLUSION: We demonstrate region-specific alterations of perivascular spaces in VP/VLBW-born adults. Data suggest that prematurity has lasting impact on the PVS.

An increasing number of epidemiological and experimental studies have demonstrated a bidirectional relationship between mood disorders and the circadian system, with disrupted circadian rhythms contributing to depressive states, and their restoration playing a key role in antidepressants effects. In this context, we sought to examine whether key molecular targets of antidepressants exhibit diurnal regulatory patterns. Naive adult male and female C57BL/6 mice were euthanized at 3-hour intervals beginning at Zeitgeber Time 0 (ZT0), and hippocampal (HC) and medial prefrontal cortex (mPFC) tissues were collected for RT-qPCR and western blot analyses. We observed statistically significant diurnal rhythmicity in all analyzed transcripts (cFos, Arc, Nr4a1, Dusp1, Dusp5, and Dusp6) in both HC and mPFC samples, with peak expression occurring during the dark (active) phase (ZT15-18). Phosphorylation levels of TrkBY816 (tropomyosin-related kinase) and GSK3{beta}S9 (glycogen synthase kinase 3{beta}) also showed periodic rhythmicity, peaking during the light (inactive) phase. Levels of p-ERK2T185/Y187 (extracellular-signal regulated kinase) did not display rhythmicity, but peaked during the light phase in the HC, especially in males. Collectively, these findings demonstrate that antidepressant targets are subject to diurnal regulation, highlighting the importance of integrating circadian biology and time-of-day as relevant variables in the development of translationally relevant antidepressant research. HighlightsO_LIKey molecular targets of antidepressants exhibit diurnal regulation in adult mice C_LIO_LIDiurnal patterns were conserved across targets, sexes, and brain regions (HC&PFC) C_LIO_LIcFos, Arc, Nr4a1, Dusp1,5,6 mRNAs display peak expression during the dark phase C_LIO_LITrkBY816 and GSK3{beta}S9 phosphorylation peak during the light (inactive) phase C_LIO_LIAntidepressant mechanisms may be linked with circadian and sleep-wake dynamics C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/716906v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1e65e60org.highwire.dtl.DTLVardef@13e302corg.highwire.dtl.DTLVardef@1ccc25forg.highwire.dtl.DTLVardef@1ed10d3_HPS_FORMAT_FIGEXP M_FIG C_FIG

Microglia are the brains resident immune cells that exhibit complex signaling behavior, including phagocytic activity in response to threats and prolonged neuronal activity. Adenosine triphosphate (ATP) is a chemoattractant for microglia. In the nucleus accumbens (NAc), ATP is co-packaged and released with DA, and microglia express dopamine (DA) receptors and ATP receptors. The present work examines microglia chemotactic motility for these transmitters using iontophoresis and multiphoton microscopy approaches in NAc brain slices from GFP-monocyte labeled transgenic mice. ATP chemoattraction was more regularly observed than DA chemoattraction, and DA chemoattraction occurred in only a small subset of microglia. The DA chemoattraction of this subset was blocked by DA D1 antagonism. Microglia are reactive oxygen species (ROS) scavengers. Application of glucose oxidase produces mild but consistent increases in ROS and induced inflammatory-related changes in microglial morphology and motility. Glucose oxidase application decreased DA release but had variable effects on ATP release. The toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) transitioned microglia from ramified to amoeboid morphology over a period of 4 hours, and increased DA and ATP release across this same period. These studies highlight the complex relationship between local immune activation and DA terminal functionality.

Early adversity increases vulnerability for adult psychopathology. Across multiple pre-clinical models of early adversity, there are reports of glial dysfunction and disrupted amino acid neurotransmission, along with maladaptive behavioral responses in adulthood. Disrupted G-protein coupled receptor signaling is known to phenocopy specific consequences of early life adversity. Enhanced Gq signaling in the forebrain excitatory neurons in early postnatal life programs anxio-depressive behaviors in adulthood, accompanied by altered neuronal glutamate and GABA metabolism in mouse models. We hypothesized that enhancing Gq signaling in forebrain excitatory neurons in early postnatal life may also impact glial function in adulthood. Our results show that postnatal hM3Dq-mediated chemogenetic activation of CaMKII-positive forebrain excitatory neurons not only increases anxiety-like behavior, but also evokes bidirectional transcriptional regulation of multiple glia-associated genes in the neocortex and hippocampi. While Gfap, Aldh1l1, S100{beta}, Eaat1, Eaat2 and Eaat3, mRNA levels were reduced in the neocortex, they were enhanced in the hippocampus, and a similar pattern was noted for GFAP protein levels. Transient, postnatal chemogenetic activation of CaMKII-positive neurons did not alter astrocyte cell density in both the neocortex and the hippocampus. Using (1H-(13C)) NMR spectroscopy, we observed a significant decline in astrocyte-specific glutamate and GABA neurotransmitter turnover, and a reduction in astrocyte metabolic flux within the neocortex and the hippocampus in adulthood in animals with a history of postnatal chemogenetic activation of forebrain excitatory neurons. Our findings indicate that chemogenetically driving Gq signaling transiently during the postnatal window in forebrain excitatory neurons results in persistent changes well into adulthood, with enhanced anxiety-like behaviors and disrupted glial function and metabolism, phenocopying specific changes in glial function noted following early adversity.

Restricted and repetitive behaviors are characteristic of several neurodevelopmental disorders. While environmental enrichment has been shown to affect these behaviors, the underlying neural mechanisms remain poorly understood. In this study, we systematically explored the effects of environmental enrichment on brain structure and microstructure in C58 mice, a model of restricted and repetitive behaviors, compared to C57 control mice. Using structural magnetic resonance imaging and diffusion-weighted imaging, we assessed regional brain volumes and microstructural properties and examined their association with behavioral outcomes. Our results revealed significant reductions in total brain volume in C58 mice, with region-specific volumetric changes following environmental enrichment exposure. Importantly, environmental enrichment promoted microstructural plasticity in both strains, with significant alterations in fractional anisotropy and fiber density. These neuroanatomical changes were linked to reductions in restricted and repetitive behaviors, with strain- and sex-dependent effects. Overall, our findings suggest that environmental enrichment remodels brain plasticity at both structural and microstructural levels, as well as behavior, providing insights into potential therapeutic approaches through environmental enrichment for neurodevelopmental disorders.

Alzheimers Disease and Related Dementias (ADRDs) are linked to reduced bone integrity and increased fracture risk, but the mechanisms that underlie this risk remain poorly defined. Current research suggests that environmental factors, such as diet, sleep, and light exposure can modulate the brain-bone axis, increasing susceptibility to bone loss and fractures. Circadian disruption (CD) associated with ADRDs may exacerbate the effects of disease and aging in the bone. In particular, regulation of bone marrow progenitors may be acutely susceptible to disruption along this axis. Here, we explore the interplay among genetic and environmental factors that influence bone structure, marrow progenitor cell activity, and monocyte-derived macrophages. The APP/PS1 transgenic mouse model (AP) is used as an in vivo model of amyloid-beta deposition. High-resolution micro-computed tomography (CT) identified sex- and genotype-specific responses in trabecular morphometry. Follow-up analysis with Raman spectroscopy (RS) found accumulation of non-enzymatic modifications of the organic matrix and notched three-point bending identified concomitant loss of bone toughness due to both CD and AP. Single-cell RNA sequencing (scRNA-seq) confirmed the presence of oxidative stress signals in the cellular populations of the bone marrow. We further mapped significantly differentially expressed genes (DEGs) from monocytes in the bone marrow to circadian-regulated proteins in monocyte-derived macrophages, revealing dysregulation of circadian timing in macrophages in vitro. These findings offer new insights into how environmental disruptions can exacerbate the progression of neurodegenerative disease and bone degradation. LAY SUMMARYPatients with Alzheimers disease have an increased bone fracture risk, but the biological link between brain and bone disease is not well understood. Everyday factors such as altered light exposure (shift work, screens late at night, etc.) can worsen outcomes in the brain and skeleton. Using a mouse model of Alzheimers disease, we found that both genetic risk and circadian disruption contribute to weaker bone and altered bone quality. We also identified inflammation and stress responses in bone marrow cells, suggesting that bone marrow may play a key role in linking brain disease to bone fragility.

BackgroundGrowing evidence suggests that sleep plays an important role in PTSD outcomes, potentially due to its influence on emotional memory consolidation, though these mechanisms remain unknown. This study sought to test the hypotheses that sleep neurophysiology, PTSD status, and sex moderates the degree to which the late positive potential (LPP) mediates memory accuracy for affective visual stimuli. MethodsN = 39 participants (18 female) viewed 75 negative and 75 neutral IAPS images while EEG was recorded. After viewing the images, participants took a two-hour long nap which was followed by a memory assessment. Memory accuracy was measured using d = Z(hit rate) - Z(false alarm rate), where hit rate refers to the proportion of images seen during the memory assessment that are correctly identified as being previously seen, false alarm rate refers to the proportion of images seen during the memory assessment that are incorrectly identified as being previously seen, and Z() is the inverse cumulative distribution function of the standard normal distribution function. ResultsThe early (300 - 1000 ms) and late (1000 - 1500 ms) LPP mediated enhanced discrimination accuracy for emotional compared to neural stimuli (d) (ps < 0.001). The association between the late LPP and d was moderated by sleep such that the association was stronger when participants spent proportionately more time in N3 and REM (p = 0.02). The differences in reactivity between emotional and neutral images for both the early and late LPP were attenuated in PTSD+ individuals vs. controls (ps < 0.001). Despite mediation results showing greater d for emotional compared to neutral stimuli, women showed overall worse memory accuracy for negative compared to neutral stimuli (p < 0.001) whereas men showed no difference (p = 0.64). ConclusionsN3 and REM sleep play a critical role for memory of stimuli that produce large and sustained neural responses. PTSD is marked by a diminished ability to distinguish between negative and neutral information. More research is critical to understand sex effects on emotional memory.

Memory impairment is a common and sometimes overlooked feature of major depressive disorder, and cognitive deficits may precede the onset of depressive symptoms in some cases. However, the cognitive benefits of first-line treatments such as SSRIs are mixed. Tianeptine is an atypical antidepressant and cognitive enhancer that neither interacts with monoamine receptors nor inhibits the reuptake of their neurotransmitters. Its antidepressant efficacy in animal models requires activation of the mu-opioid receptor (mu-OR) and phosphorylation of the AMPA receptor. However, the receptors that mediate its memory enhancing actions have never been investigated. We therefore tested the ability of tianeptine to improve spatial memory in a cross-maze task in wild-type (WT) mice compared to its effects in mice with global knockout of either the mu-OR or delta-OR. In parallel, we assessed the effects of tianeptine on hippocampal oscillatory activity and spontaneous locomotion in the same genotypes. Adult male and female WT, mu -/-, and delta -/- mice on a C57BL/6J background were implanted with hippocampal electrodes for the recording of local field potential (LFP) oscillations. Consistent with our previous observations in anaesthetised rats, injection of tianeptine (10 mg/kg and 30 mg/kg SC) caused a dose-dependent increase in beta-frequency power in WT mice that was maximal at circa 25 Hz. The same effect was observed in delta -/- mice, but the increase in beta was completely absent in mu -/- animals. As others have reported previously, tianeptine also caused a mu-OR-dependent increase in spontaneous locomotor activity, but with a time-course that was distinct from the increase in beta power. Separate groups of WT, mu -/-, and delta -/- mice were tested for their ability to learn a food-rewarded spatial memory task in a cross-maze. Over a 20-day training period, sub-groups of each genotype received either tianeptine (10 mg/kg SC) or vehicle injection 30 min before testing. Tianeptine increased the percentage of correct trials and the number of allocentric (place) responses in WT mice, but did not enhance memory in either mu -/- or delta -/- mice, even though both genotypes were able to learn the task. These results indicate that the ability of tianeptine to drive hippocampal beta oscillations is dependent on the mu-OR, whereas its memory-enhancing actions require the presence of both mu- and delta-ORs. The latter result is consistent with the actions of tianeptine on postsynaptic AMPA receptors, and we are currently exploring the signalling pathways involved in this process.

Astrocytes are the most abundant glial cells in the brain and an integrative component of the neural network. Studies have shown that ethanol altered expression of an astrocyte marker, i.e., glial fibrillary acidic protein (GFAP), in two key corticolimbic regions, the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). These regions comprise anatomically and functionally different subregions, i.e., the prelimbic (PL) and infralimbic (IL) cortex of the mPFC, the shell and core subregions of the NAc. However, ethanol effects on GFAP expression within these subregions remain largely unknown. In addition, effects of pharmacological manipulation of astrocytes on alcohol drinking have been understudied. Western blot was conducted to determine GFAP expression in subregions of the mPFC and NAc after chronic ethanol drinking. Fluorocitrate, an astrocyte-specific metabolic inhibitor, was administered to inhibit astrocytes and was tested on ethanol drinking. Ethanol drinking enhanced GFAP protein expression in the PL cortex and NAc core, but not in the IL cortex or NAc shell. Intra-ventricular administration of fluorocitrate reduced ethanol intake and preference, but increased water consumption during choice ethanol drinking. In addition, fluorocitrate did not affect total fluid consumption or basal locomotor activity. These results indicate that chronic ethanol drinking induced GFAP elevation in a subregion-specific manner within the mPFC and NAc, and that metabolic inhibition of astrocytes selectively attenuated ethanol drinking without non-specific effects on water drinking or general activity. Together, these results suggest that astrocytes may play an important role in ethanol drinking. HighlightsO_LIEthanol drinking enhanced GFAP levels in the PL cortex and NAc core. C_LIO_LIFluorocitrate inhibition of astrocytes reduced intermittent ethanol drinking. C_LIO_LIFluorocitrate did not alter total fluid consumption or basal locomotor activity. C_LI

Previous research has demonstrated that children exhibit superior - as compared to adults - consolidation of newly acquired motor sequences across post-learning periods of wakefulness. Given that consolidation is thought to be supported by the reactivation of learning-related patterns of brain activity during the rest periods following active task practice, we hypothesized that the childhood advantage in offline consolidation may be linked to greater reactivation during post-learning wakefulness. Twenty-two children (7-11 years) and 23 adults (18-30 years) completed two sessions of a motor sequence learning task, separated by a 5-hour wake interval. Multivoxel analyses of task-related and resting-state functional magnetic resonance imaging data were employed to assess the persistence of learning-related patterns of neural activity into post-task rest epochs, reflective of reactivation processes. Behavioral results demonstrated the previously reported childhood advantage in offline consolidation over a post-learning wake interval. Imaging results revealed that children exhibited greater persistence of task-related hippocampal - but not putaminal - activity into post-learning rest as compared to adults. These findings suggest that the childhood advantage in awake motor memory consolidation may be supported, at least partially, by enhanced reactivation of task-dependent hippocampal activity patterns during offline epochs.

Chronic short sleep (CSS) is an emerging public health issue that frequently begins in adolescence and is common among healthcare professionals and others engaged in shift work. Epidemiological studies associate CSS and sleep disruption with metabolic disorders, cardiovascular disease, cognitive decline, and heightened Alzheimers disease risk. Building on our prior findings that sleep deprivation perturbs proteostasis and activates endoplasmic reticulum (ER) stress pathways, we investigated the long-term consequences of CSS in young adult wild-type mice over the course of one year. Mice exposed to CSS displayed impaired cognition in hippocampal dependent tasks by 28 weeks of age, indicating emerging memory deficits. At the molecular level, CSS disrupted hippocampal proteostasis--particularly protein folding processes--and triggered ER stress and activation of the unfolded protein response (UPR). Importantly, disrupted proteostasis preceded the behavioral decline, with diminution of the key chaperone and UPR regulator BiP occurring at 20-22 weeks of age. CSS also increased markers of cellular stress and neuroinflammation while reducing the expression of proteins associated with memory function. Age also seemed to be a cellular stressor, causing a longitudinal increase in UPR, ISR, and neuroinflammation markers. Together, these results indicate that both chronic short sleep and age compromise proteostasis and promote neuroinflammation, contributing to progressive cognitive dysfunction.

Brain networks that support episodic memory development in the first years of life remain poorly understood. Protracted growth of regions such as the hippocampus have been suggested as a causal role in episodic memory development, but development of these memory brain networks and their role in episodic memory development is not yet fully elucidated. In this study, subcortical memory network regions (hippocampus, thalamus, amygdala) were segmented from MRI images in 835 visits spanning 0-4 years of age across 322 participants in the Baby Connectome Project. Hippocampal segmentations were further subdivided into head, body, and tail subregions manually for 426 visits, which were used to train models that automatically segmented hippocampal subregions for the remaining visits. 58 participants returned for an early school-age follow-up, including two episodic memory tasks. Volumetric growth trajectories differed across regions and across subregions within the hippocampus, with the head of the hippocampus showing steep growth that plateaued months later than the body or tail of the hippocampus. In the right hemispheres hippocampal head, age- and sex- adjusted volumes positively predicted future early school-age episodic memory performance. After accounting for total brain volume, the right thalamus also predicted memory performance. Total sleep duration at the follow-up visit accounted for performance variance above and beyond brain volume correlations. Altogether, results suggest that trajectories of growth and relationships between volume and episodic memory performance are region and subregion specific, and provide evidence for the important role of sleep in associations between brain networks and early episodic memory development. SignificanceThe hippocampus is a critical structure in episodic memory, yet precise longitudinal developmental trajectories of this structure have yet to be elucidated. This study provides detailed, subregion specific hippocampal trajectories, and demonstrates that variation in these trajectories is associated with variation in later episodic memory performance. This insight fills a current gap in the literature delineating how brain development and episodic memory behaviors are related in the first five years of life. Considering this is the same age range during which adults begin to have long-term memories available from childhood, this gap represents an important opportunity to understand how changes in the brain support the development of basic episodic memory skills.

Chronotype reflects individual circadian preference for timing of sleep, wakefulness, and peak performance and has been linked to variability in prefrontal cognitive function across the day. Whether chronotype independently relates to dual-task gait cost (DTC) and whether this relationship differs by cognitive task domain is unclear. Sixty-nine healthy young adults (37 female; mean age 21.3 years) completed the Morningness-Eveningness Questionnaire (MEQ). Spatiotemporal gait parameters were recorded with three-dimensional motion capture during single-task walking and three dual-task conditions: backward word spelling (5LWB; phonological), serial subtraction by seven (SS7; arithmetic), and reverse month recitation (RMR; sequential). DTC was calculated for eight gait parameters. Condition differences were assessed with nonparametric tests and post-hoc comparisons. Multiple linear regression, adjusting for age, sex, BMI, and baseline gait velocity, tested the independent association between MEQ score and mean velocity DTC; exploratory Spearman correlations examined other parameters. SS7 produced the largest mean velocity DTC (-12.76%), significantly greater than 5LWB (-7.95%; p = 0.002) and RMR (-9.57%; p = 0.021). MEQ score independently predicted mean velocity DTC in 5LWB ({beta} = -0.51, p < 0.001, R{superscript 2} = 0.269) and RMR ({beta} = -0.55, p = 0.004, R{superscript 2} = 0.222), indicating greater morningness associated with better gait-speed preservation under cognitive load; the SS7 association was not significant ({beta} = -0.33, p = 0.071). Exploratory correlations showed MEQ-DTC associations across 7/8 parameters in 5LWB, 4/8 in RMR, and 3/8 in SS7. Chronotype is independently associated with dual-task gait cost in a task-domain-specific manner, with stronger effects for phonological and sequential tasks than for arithmetic processing. The SS7 condition yielded the largest interference but weakest chronotype modulation, suggesting arithmetic dual-task disruption may be less sensitive to circadian arousal. Fixed testing time and cross-sectional design warrant within-subject, multi-timepoint studies to confirm chronotype effects separate from time-of-day confounds.

The brain continuously integrates information from the external environment (exteroception) and the internal bodily milieu (interoception). How the balance between these two processing streams shifts across vigilance states with differing levels of environmental responsiveness, however, remains poorly understood. Here, we examined neural responses to external auditory and internal cardiac signals across wakefulness and REM sleep microstates - tonic and phasic REM - which are characterized by progressively reduced responsiveness to external stimulation. High-density EEG was recorded in healthy participants (n=25). Auditory evoked potentials (AEPs) and heartbeat evoked potentials (HEPs) served as indices of exteroception and interoception, respectively, and were compared across vigilance states. AEPs progressively decreased from wakefulness to tonic REM and were most attenuated during phasic REM. In contrast, HEPs were preserved across REM microstates and were enhanced relative to wakefulness, indicating sustained - and even amplified - processing of cardiac signals during REM sleep. To quantify the relative weighting of external and internal signals, we introduce an exteroceptive-interoceptive index, defined as the ratio of auditory to cardiac neural responses. This index decreased systematically across vigilance states, revealing a graded shift from externally oriented processing during wakefulness to internally oriented processing during phasic REM, with tonic REM occupying an intermediate position. Together, these findings demonstrate that while responsiveness to external stimuli diminishes during phasic REM, the brain continues to prioritize physiologically relevant internal signals. The exteroceptive-interoceptive balance may thus provide a novel, mechanistically grounded marker of altered consciousness, particularly informative in contexts where behavioural responsiveness cannot be assessed. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/712081v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1e46a9borg.highwire.dtl.DTLVardef@112f050org.highwire.dtl.DTLVardef@5f5249org.highwire.dtl.DTLVardef@135cc4_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundTraumatic brain injury (TBI) together with non-cerebral injuries characterizes the TBI-polytrauma (P-TBI) constellation, which is associated with acute neurological deterioration, delirium and unfavourable prognosis. It is hypothesized that systemic inflammatory mediators my enhances the focal, cerebral neuroimmune reaction with overall detrimental consequences, in particular in terms of acute microglial reactivity. MethodsWe explored the role of the Complement factor 3 (C3) and of the TLR-co receptor cluster of differentiation (CD14) in a murine polytrauma model that involves a mild TBI together with femur fracture, blunt thorax trauma and resuscitated haemorrhagic shock, making use of mice genetically lacking either C3, CD14 or both. ResultsWe show that P-TBI results in a rapid (4h) and brain-wide induction of inflammatory cytokines, although with distinct profiles (TNF and CCL2 having brain-wide involvement and IL-1{beta} restricted to ipsilateral cortex and striatum). TNF and CCL2 mRNA as well as protein synthesis were upregulated in microglia upon P-TBI in cortex, hippocampus and striatum which was fully abolished in the C3-/-CD14-/-animals. The analysis of single-KO animals revealed that induction of TNF and CCL2 was prevented in animals lacking C3, but not CD14, in the contralateral cortex and striatum, with an abolishment in hippocampus in mice lacking both C3 and CD14. In the cortical area of focal lesion neither C3 nor CD14 affected the induction of pro-inflammatory cytokines. ConclusionThus, C3 and CD14 are dispensable for the acute cytokine response to P-TBI in the site of injury but play differential roles across the cortex, hippocampus and striatum for the induction of cytokines in the non-injured parenchyma and in particular in microglia. Thus, interventions on C3 (mainly) and/or CD14 may reduce the encephalopathy risk associated with P-TBI but not the acute response in the injury site, where additional DAMP signalling may offer redundant activation pathways.

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder caused by the loss of paternally expressed genes within the imprinted 15q11-q13 locus, which includes clusters of box C/D small nucleolar RNAs (SNORDs), notably the SNORD115 and SNORD116 gene families. Although paternally inherited SNORD116 deletions have been associated with sleep disturbances in patients and mouse models, the respective and combined contributions of SNORD115 and SNORD116 to sleep regulation remain unclear. Here, we combined polysomnographic recordings with quantitative analysis of hypothalamic neuronal populations to assess sleep-wake architecture, sleep homeostasis, and underlying circuit alterations in mice carrying paternal deletions of SNORD115, SNORD116, or both clusters. SNORD116 deletion was associated with a selective increase in REM sleep, particularly during the light phase and during recovery following sleep deprivation, without affecting slow-wave sleep or REM-associated theta activity. In contrast, SNORD115 deletion did not alter sleep. Unexpectedly, combined deletion of SNORD115 and SNORD116 did not reproduce the REM sleep phenotype observed in SNORD116-deficient mice, indicating that SNORD115 loss attenuates SNORD116-dependent REM sleep alterations. At the cellular level, melanin-concentrating hormone (MCH) neuron density was reduced in both SNORD116-KO and double SNORD116/115-KO mice, whereas hypocretin (Hcrt) neurons were preserved across genotypes. Notably, REM sleep alterations did not parallel MCH loss, as increased REM sleep was absent in double-KO animals despite comparable reduction in MCH neuron density. Transcriptomic analyses at ZT0 further revealed only limited changes in hypothalamic gene expression across models. Together, these findings reveal an unanticipated interaction between SNORD115 and SNORD116 in the regulation of REM sleep and uncover a dissociation between genetic alterations, neuronal circuit organization, and sleep phenotype. More broadly, they caution against inferring physiological functions or disease-relevant mechanisms from single SNORD deletions within complex imprinted loci, and indicate that current mouse models may not faithfully capture sleep alterations associated with PWS.

Traumatic Brain Injury (TBI) patients may suffer from a number of long-term complications after injury such as impaired motor skills, cognitive decline, and sensory abnormalities including chronic pain. Disruption of endogenous pain modulatory pathways likely contributes to development of chronic pain in a wide range of conditions including TBI. Aerobic exercise has been shown to impact pain syndromes. Here we investigate the effect of exercise on pain outcome measures after TBI using a lateral fluid percussion (LFP) model and voluntary running wheels in male and female rats. We tested mechanical nociceptive reactivity with von Frey fibers and descending control of nociception (DCN) using hindpaw sensitization with PGE2 followed by a capsaicin-test stimulus to the forepaw. Pharmacological studies employed the administration of noradrenergic (NA) and serotoninergic receptor blockers. Neuropathological studies quantified neuroinflammatory changes and axonal damage. We found that exercise decreased the duration of the acute phase of pain from [~]5 weeks to 2-3 weeks in female and male TBI rats respectively, gains that could be reversed using the 1-adrenoceptor (1AR) antagonist, prazosin. Exercise also prevented the loss of DCN for at least 180 days post-injury in both male and female TBI rats. The intact DCN response in male and female TBI rats provided by exercise could be blocked using prazosin. Surprisingly, exercise-mediated restoration of the DCN response in male TBI rats was not blocked by the 5-HT7 receptor antagonist, SB-267790, the receptor system through which serotonin reuptake inhibitors restore DCN after TBI in male rats. Therefore, the transition from a noradrenergic to a serotonergic inhibitory pain pathway that we typically see in male TBI rats, was blocked by exercise. Assessment of neuropathology, acutely after TBI, reveals that both the astrocyte and microglial response to injury is significantly greater in male TBI compared to female TBI, regardless of exercise. The effect of exercise on the extent of neuroinflammation after injury was minimal in TBI rats of both sexes. In contrast, exercise significantly decreased the amount of axonal loss in the corpus callosum in both male and female TBI rats compared to sedentary TBI rats. However, the extent of axonal loss after TBI in both exercise and sedentary male rats was greater than in female exercise and sedentary groups respectively. These results demonstrate that exercise is a promising treatment for chronic pain after TBI in both male and females. It also highlights that dysfunction of the endogenous pain modulatory pathways observed in male rats after TBI can be prevented by exercise, possibly by reducing axonal loss.

The circadian clock controls a vast array of cellular and organismal functions, from the molecular scale to behavior. While each cell is regimented by a cell-autonomous clock, few studies in the brain have dissected the circuit and behavioral contributions of cell-specific clocks. Relatedly, astrocytes are now known to play key roles in regulating synaptic function, circuit activity and behavior, but whether these functions are guided by astrocyte-autonomous clocks is unknown. Here, we report that post-natal deletion of the critical circadian clock gene Bmal1 in astrocytes, which abrogates core clock function in a cell type specific manner, induced expression of genes related to extracellular matrix (ECM) production, maintenance, and remodeling. Circadian variations have been shown in a specific ECM structure, perineuronal nets (PNNs), which are implicated in synaptic function and plasticity. In astrocyte-specific Bmal1 knockouts, hippocampal PNN abundance was decreased, and the circadian rhythm of these structures was also abolished. In line with evidence implicating PNNs, and the ECM in general, in synaptic function and plasticity, we found that astrocyte-specific Bmal1 KO mice had increased synaptic strength but blunted long term potentiation (LTP), as well as impaired learning and memory performance in a novel object recognition task. Taken together, these findings suggest that the astrocyte circadian clock regulates circadian rhythms in perineuronal net abundance as well as synaptic plasticity and behavioral learning and memory.