bioRxiv Subject Collection: Neuroscience's Journal

Decoding Cortical Circuits: Synaptic Signatures and Disease Vulnerabilities of Layer 5 Pyramidal Neuron Types
Cortical layer 5 (L5) intratelencephalic (IT) and pyramidal tract (PT) neurons are embedded in distinct information processing pathways. Despite their significance for cognitive function, it remains poorly understood how L5 neuron types are connected into circuits and how this might be perturbed in disease. Utilizing an optimized proximity biotinylation workflow, we characterize the excitatory postsynaptic proteomes of L5 IT and PT neurons in intact somatosensory circuits. We find distinct molecular synaptic signatures of L5 IT and PT neurons defined by proteins regulating synaptic transmission and organization, suggesting that these contribute to function and input connectivity of L5 neuron types. The synaptic signature of L5 IT, but not of PT, neurons displays a marked enrichment of autism risk genes, aligning with previous studies highlighting the vulnerability of IT neurons and suggesting that the excitatory postsynaptic compartment of L5 IT neurons is notably susceptible in autism. Our analysis sheds light on the proteins that govern circuit integration and function of L5 neuron types and underlie their susceptibility in disease. Moreover, our approach is broadly applicable to other neuron types and circuits.

TDP-43 nuclear loss in FTD/ALS causes widespread alternative polyadenylation changes
In frontotemporal dementia and amyotrophic lateral sclerosis, the RNA-binding protein TDP-43 is depleted from the nucleus. TDP-43 loss leads to cryptic exon inclusion but a role in other RNA processing events remains unresolved. Here, we show that loss of TDP-43 causes widespread changes in alternative polyadenylation, impacting expression of disease-relevant genes (e.g., ELP1, NEFL, and TMEM106B) and providing evidence that alternative polyadenylation is a new facet of TDP-43 pathology.

Individual variability in neural representations of mind-wandering
Mind-wandering is a frequent, daily mental activity, experienced in unique ways in each person. Yet neuroimaging evidence relating mind-wandering to brain activity, for example in the default mode network (DMN), has relied on population- rather than individual-based inferences due to limited within-individual sampling. Here, three densely-sampled individuals each reported hundreds of mind-wandering episodes while undergoing multi-session functional magnetic resonance imaging. We found reliable associations between mind-wandering and DMN activation when estimating brain networks within individuals using precision functional mapping. However, the timing of spontaneous DMN activity relative to subjective reports, and the networks beyond DMN that were activated and deactivated during mind-wandering, were distinct across individuals. Connectome-based predictive modeling further revealed idiosyncratic, whole-brain functional connectivity patterns that consistently predicted mind-wandering within individuals but did not fully generalize across individuals. Predictive models of mind-wandering and attention that were derived from larger-scale neuroimaging datasets largely failed when applied to densely-sampled individuals, further highlighting the need for personalized models. Our work offers novel evidence for both conserved and variable neural representations of self-reported mind-wandering in different individuals. The previously-unrecognized inter-individual variations reported here underscore the broader scientific value and potential clinical utility of idiographic approaches to brain-experience associations.

Comparison of whole-brain task-modulated functional connectivity methods for fMRI task connectomics
Higher brain functions require flexible integration of information across widely distributed brain regions depending on the task context. Resting-state functional magnetic resonance imaging (fMRI) has provided substantial insight into large-scale intrinsic brain network organisation, yet the principles of rapid context-dependent reconfiguration of that intrinsic network organisation are much less understood. A major challenge for task connectome mapping is the absence of a gold standard for deriving whole-brain task-modulated functional connectivity matrices. Here, we performed biophysically realistic simulations to control the ground-truth task-modulated functional connectivity over a wide range of experimental settings. We revealed the best-performing methods for different types of task designs and their fundamental limitations. Importantly, we found that rapid (100 ms) modulations of oscillatory neuronal synchronisation can be recovered from sluggish haemodynamic fluctuations even at typically low fMRI temporal resolution (2 s). Finally, we provide practical recommendations on task design and statistical analysis to foster task connectome mapping.

Aging and injury drive neuronal senescence in the dorsal root ganglia
Aging negatively impacts central nervous system function; however, the cellular impact of aging in the peripheral nervous system remains poorly understood. Aged individuals are more likely to experience increased pain and slower recovery after trauma. Such injury can damage vulnerable peripheral axons of dorsal root ganglion (DRG) neurons resulting in somatosensory dysfunction. One cellular mechanism common to both aging and injury is cellular senescence, a complex cell state that can contribute to the aged pro-inflammatory environment. We uncovered, for the first time, DRG neuron senescence in the context of aging and pain-inducing peripheral nerve injury in young and aged mice. Aged DRG neurons displayed multiple markers of senescence (SA-{beta}-gal, p21, p16, IL6) when compared to young DRG neurons. Peripheral nerve injury triggered a further accumulation of senescent DRG neurons over time post-injury in young and aged DRG. These senescent neurons were dynamic and heterogeneous in their expression of senescence markers, p16, p21, and senescence-associated secretory phenotype (SASP) expression of IL6, which was influenced by age. An electrophysiological characterization of senescence marker-expressing neurons revealed high-firing and nociceptor-like phenotypes within these populations. In addition, we observed improvement in nociceptive behaviors in young and aged nerve-injured mice after treatment with a senolytic agent that eliminates senescent cells. Finally, we confirmed in human post-mortem DRG samples that neuronal senescence is present and increases with age. Overall, we describe a susceptibility of the peripheral nervous system to neuronal senescence with age or injury that may be a targetable mechanism to treat sensory dysfunction, such as chronic pain, particularly in aged populations.

Explorations of using a convolutional neural network to understand brain activations during movie watching
Neuroimaging studies increasingly use naturalistic stimuli like video clips to trigger complex brain activations, but the complexity of such stimuli makes it difficult to assign specific functions to the resulting brain activations, particularly for higher-level content like social interactions. To address this challenge, researchers have turned to deep neural networks, e.g., convolutional neural networks (CNNs). CNNs have shown success in image recognition due to their different levels of features enabling high performance. In this study, we used pre-trained VGG-16, a popular CNN model, to analyze video data and extract hierarchical features from low-level shallow layers to high-level deeper layers, linking these activations to different levels of activation of the human brain. We hypothesized that activations in different layers of VGG-16 would be associated with different levels of brain activation and visual processing hierarchy in the brain. We were also curious about which brain regions would be associated with deeper convolutional layers in VGG-16. The study analyzed a functional MRI (fMRI) dataset where participants watched the cartoon movie Partly Cloudy. Frames of the videos were fed into VGG-16, and activation maps from different kernels and layers were extracted. Time series of the average activation patterns for each kernel were created and fed into a voxel-wise model to study brain activations. Results showed that lower convolutional layers (1st convolutional layer) were mostly associated with lower visual regions, but some kernels (6, 19, 24, 42, 55, and 58) surprisingly showed associations with activations in the posterior cingulate cortex, part of the default mode network. Deeper convolutional layers were associated with more anterior and lateral portions of the visual cortex (e.g., the lateral occipital complex) and the supramarginal gyrus. Analyzing activation features associated with different brain regions showed the promise and limitations of using CNNs to link video content to brain functions.

Spontaneous oxycodone withdrawal disrupts sleep, circadian, and electrophysiological dynamics in rats
Opioid dependence is defined by an aversive withdrawal syndrome upon drug cessation that can motivate continued drug-taking, development of opioid use disorder, and precipitate relapse. An understudied but common opioid withdrawal symptom is disrupted sleep, reported as both insomnia and daytime sleepiness. Despite the prevalence and severity of sleep disturbances during opioid withdrawal, there is a gap in our understanding of their interactions. The goal of this study was to establish an in-depth, temporal signature of spontaneous oxycodone withdrawal effects on the circadian composition of discrete sleep stages and the dynamic spectral properties of the electroencephalogram (EEG) signal in male rats. We continuously recorded EEG and electromyography (EMG) signals for 8 d of spontaneous withdrawal after a 14-d escalating-dose oxycodone regimen (0.5 - 8.0 mg/kg, 2xd; SC). During withdrawal, there was a profound loss and gradual return of circadian structure in sleep, body temperature, and locomotor activity, as well as increased sleep and wake fragmentation dependent on lights on/off. Withdrawal was associated with significant alterations in the slope of the aperiodic 1/f component of the EEG power spectrum, an established biomarker of arousal level. Early in withdrawal, NREM exhibited an acute flattening and return to baseline of both low (1-4 Hz) and high (15-50 Hz) frequency components of the 1/f spectrum. These findings suggest temporally dependent withdrawal effects on sleep, reflecting the complex way in which the allostatic forces of opioid withdrawal impinge upon sleep and circadian processes. These foundational data based on continuous tracking of nocturnal rhythms, sleep stage composition, and spectral EEG properties provide a detailed construct with which to form and test hypotheses on the mechanisms of opioid-sleep interactions.

Task-related modulation of event-related potentials does not reflect changes to sensory representations
Attention supports efficient perception by increasing the neural signals of targets while supressing the those of distractors. Decades of work studying the event-related potentials of electroencephalography (EEG) recordings have established our understanding of attention in the human brain, but many aspects of this phenomenon remain unknown. Several recent studies suggest that multivariate analyses may provide new insights into how attention shapes the neural representations of stimuli; however, it is unclear whether the increased multivariate decoding accuracy associated with task relevance represents a change in the stimulus representation or an additional cognitive process. To understand what the change in multivariate information that is associated with task relevance reflects, here we used inverted encoding to characterize how task relevance shapes the neural representation of space and colour. For both spatial and feature-based tasks, we found that the change in the EEG recordings associated with task relevance is not related to the stimulus representation. Rather, our findings indicate that this phenomenon reflects an additional cognitive process, such as target recognition.

Giant pyramidal neurons of the primary motor cortex express vasoactive intestinal polypeptide (VIP), a known marker of cortical interneurons
Vasoactive intestinal polypeptide (VIP) is known to be present in a subclass of cortical interneurons that are involved in the disinhibition of excitatory pyramidal neurons. Here, using three different antibodies, we demonstrate that VIP is also present in the giant layer 5 pyramidal (Betz) neurons which are characteristic of the limb and axial representations of the marmoset primary motor cortex (cytoarchitectural area 4ab). No VIP staining was observed in smaller layer 5 pyramidal cells present in the primary motor facial representation (cytoarchitectural area 4c), or in premotor cortex (e.g. the caudal subdivision of the dorsal premotor cortex, A6DC), indicating the selective expression of VIP in Betz cells. The most intense VIP staining occurred in the largest Betz cells, located in the medial part of A4ab. VIP in Betz cells was colocalized with neuronal specific marker (NeuN) and a calcium-binding protein parvalbumin (PV). PV also intensely labelled axon terminals surrounding Betz cell somata. Whereas Betz cells bodies were located in layer 5, VIP-positive (VIP+) interneurons were more abundant in the superficial cortical layers. They constituted about 5-7% of total cortical neuronal population, with the highest density observed in area 4c. Our results demonstrate the expression of VIP in the largest excitatory neurons of the primate cortex, which may offer new functional insights into the role of VIP in the brain, and also provide opportunities for genetic manipulation of Betz cells.

Developmental order, fibre caliber, and vascularization predict tract-wise declines: Testing retrogenesis and physiological predictions in white matter aging
To understand the consistently observed spatial distribution of white-matter (WM) aging, developmentally driven theories of retrogenesis have gained traction, positing that the order WM development predicts declines. Regions that develop first are often expected to deteriorate the last, i.e. "last-in-first-out". Alternatively, regions which develop most rapidly may also decline most rapidly in aging, or the "gains-predict-loss" model. The validity of such theories remains uncertain, in part due to lack of clarity on the definition of developmental order. Our recent findings also suggest that WM degeneration may vary by physiological parameters such as perfusion. Furthermore, it is informative to link perfusion to fibre metabolic need, which varies with fibre size. Here we address the question of whether WM degeneration is determined by development trajectory or physiological state across both microstructural and perfusion measures using data drawn from the Human Connectome Project in Aging (HCP-A). Our results indicate that developmental order of tract myelination provides the strongest support for the retrogenesis hypothesis, with the last to complete myelination the first to decline. Moreover, higher mean axon diameter and lower macrovascular density are associated with lower degrees of WM degeneration across measures. Tract perfusion, in turn also tends to be higher and the arterial transit time longer for tracts that appear first. These findings suggest that WM degeneration in different tracts may be governed by their developmental trajectories and physiology, and ultimately influenced by each tract's metabolic demand.

Obesity differentially effects the somatosensory cortex and striatum of TgF344-AD rats
Lifestyle choices leading to obesity, hypertension and diabetes in mid-life contribute directly to the risk of late-life Alzheimer's disease (AD). However, in late-life or in late-stage AD conditions, obesity reduces the risk of AD and disease progression. To examine the mechanisms underlying this paradox, TgF344-AD rats were fed a varied high-carbohydrate, high-fat (HCHF) diet to induce obesity from nine months of age representing early stages of AD to twelve months of age in which rats exhibit the full spectrum of AD symptomology. We hypothesized regions primarily composed of gray matter, such as the somatosensory cortex (SSC), would be differentially affected compared to regions primarily composed of white matter, such as the striatum. We found increased myelin and oligodendrocytes in the somatosensory cortex of rats fed the HCHF diet with an absence of neuronal loss. We observed decreased inflammation in the somatosensory cortex despite increased AD pathology. Compared to the somatosensory cortex, the striatum had fewer changes. Overall, our results suggest that the interaction between diet and AD progression affects myelination in a brain region specific manner such that regions with a lower density of white matter are preferentially effected. Our results offer a possible mechanistic explanation for the obesity paradox.

Memory consolidation during rest forms shortcuts in a cognitive map
Rest and sleep not only strengthen existing memories but also reorganise memories to generate new knowledge that extends beyond direct experience. It remains unclear how this reorganisation affects behaviour. Here, to investigate the behavioural consequences of reorganising memories, we designed a novel protocol to promote memory consolidation during rest using awake, contextual targeted memory reactivation (TMR). We found that promoting memory consolidation during rest improves the ability to make novel inferences by forming 'shortcuts' between memories which have not been experienced together. These shortcuts in memory extend beyond direct experience to facilitate inference. However, these shortcuts impair our ability to flexibly update memories in response to changes in the environment. These findings demonstrate how memories are reorganised during awake rest to construct a cognitive map of our environment that sets a trade-off between efficient and flexible behaviour.

Selective attention modulates feature accumulation speed during perception and memory retrieval
Mounting evidence has elucidated the sequential information processing trajectory, progressing from low-level perceptual to higher-level conceptual features during visual object recognition and reversing during memory retrieval. However, the extent to which the processing stream can be modulated by selective attention, as dictated by task requirements, remains unclear. The present study combined convolutional neural network (AlexNet), drift-diffusion model and multivariate decoding analysis to address this question. By using single-trial-based multivariate decoding analysis, we tracked the onset and peak time of feature representations across various visual perceptual and mnemonic categorization tasks, encompassing color, animacy, and size feature categorization. The findings of this study revealed several key outcomes: (1) A significant increase in reaction time was observed for the visual perception of color, animacy, and size features. (2) The findings from AlexNet and the drift-diffusion model revealed that, despite a parallel processing nature in these three features, those with larger decision boundaries necessitate subjects to spend more reaction time in making decisions about them. (3) In perceptual tasks, selective attention induced a reversal in the onset time of perceptual and conceptual features in the occipital and parietal lobe, resulting in the earlier detection of conceptual features compared to perceptual features. Conversely, in mnemonic tasks, selective attention led to the precedence of the peak time of perceptual features over conceptual features in the frontal lobe, signifying the reactivation of perceptual features with the highest fidelity prior to conceptual features. (4) Phase coupling analysis indicated a reversed information flow in the beta band during the task preparation stage in visual perception and memory retrieval tasks. Additionally, interactions between the occipital and temporal lobes in the theta band during the task preparation stage were found to promote an earlier onset time of target features in the visual perception stage. Collectively, these results underscore the parallel processing nature of features and demonstrate that the speed of feature information accumulation can be modulated by task requirements, with a more pronounced effect observed during perceptual compared to mnemonic stages.

A Vector System Encoding Histone H3 Mutants Facilitates Manipulations of the Neuronal Epigenome
The differentiation of developmental cell lineages is associated with genome-wide modifications in histone H3 methylation. However, the causal role of histone H3 methylation in transcriptional regulation and cell differentiation has been difficult to test in mammals. The experimental overexpression of histone H3 mutants carrying lysine-to-methionine (K-to-M) substitutions has emerged as an alternative tool for inhibiting the endogenous levels of histone H3 methylation at specific lysine residues. Here, we leverage the use of histone K-to-M mutants by creating Enhanced Episomal Vectors that enable the simultaneous depletion of multiple levels of histone H3 lysine 4 (H3K4) or lysine 9 (H3K9) methylation in projection neurons of the mouse cerebral cortex. Our approach also facilitates the simultaneous depletion of H3K9 and H3K27 trimethylation (H3K9me3 and H3K27me3, respectively) in cortical neurons. In addition, we report a tamoxifen-inducible Cre-FLEX system that allows the activation of mutant histones at specific developmental time points or in the adult cortex, leading to the depletion of specific histone marks. The tools presented here can be implemented in other experimental systems, such as human in vitro models, to test the combinatorial role of histone methylations in developmental fate decisions and the maintenance of cell identity.

Spreading depolarization causes reversible neuronal mitochondria fragmentation and swelling in healthy, normally perfused neocortex.
Mitochondrial function is tightly linked to their morphology, and fragmentation of dendritic mitochondria during noxious conditions suggests loss of function. In the normoxic cortex, spreading depolarization (SD) is a phenomenon underlying migraine aura. It is unknown whether mitochondria structure is affected by normoxic SD. In vivo two-photon imaging followed by quantitative serial section electron microscopy (ssEM) was used to monitor dendritic mitochondria in the normoxic cortex of urethane-anesthetized mature male and female mice during and after SD initiated by focal KCl microinjection. Structural dynamics of dendrites and their mitochondria were visualized by transfecting excitatory, glutamatergic neurons of the somatosensory cortex with bicistronic AAV, which induced tdTomoto labeling in neuronal cytoplasm and mitochondria labeling with roGFP. Normoxic SD triggered a rapid fragmentation of dendritic mitochondria alongside dendritic beading, both reversible; however, mitochondria took significantly longer to recover. Several rounds of SD resulted in transient mitochondrial fragmentation and dendritic beading without accumulating injury, as both recovered. SsEM corroborated normoxic SD-elicited dendritic and mitochondrial swelling and transformation of the filamentous mitochondrial network into shorter, swollen tubular and globular structures. Our results revealed normoxic SD-induced disruption of the dendritic mitochondrial structure that might impact mitochondrial bioenergetics during migraine with aura.

A new insight into the role of CART peptide in serotonergic function and anxiety
Cocaine and amphetamine-regulated transcript (CART) peptide has been established as a contributor to anxiogenic behavior. Genetic mutations in the CART gene are associated with anxiety and depression, and increased CART expression has been reported in suicide victims. Extensive research has focused on the role of CART peptide in mesolimbic neurocircuitry, but its involvement in the dorsal raphe nucleus (DRN) and serotonin (5HT) system remains unexplored. Here we demonstrate that CART processes are proximal to 5HTDRN neurons and that microinjection of CART (55-102) peptide into the DRN has an anxiogenic effect in mice. Furthermore, central CART administration reduced cfos activation in 5HT neurons of the ventral DRN, which is a putative reward/anti-stress circuit. The inhibitory effect of CART on 5HTDRN neuronal function and local 5HT release is further demonstrated with in vivo fiber photometry coupled with calcium and 5HT biosensors and by mass spectrometry. Moreover, using Credependent retrograde tracing, we observed DRN projecting CART neurons in the Edinger Westphal nucleus (EW), nucleus accumbens (NAc), and various hypothalamic nuclei including the ventromedial hypothalamus (VMH). Interestingly, based on ex vivo electrophysiological recordings, acute stress increased excitability in DRN projecting CART neurons located in the EW, but not in the VMH or NAc. This suggests that the stress may promote anxiety-like behavior by activating the EW CART-5HT DRN circuit that ultimately inhibits 5HT transmission. In sum, understanding the intricate dynamics of the CARTergic and 5HTergic systems proves crucial in addressing 5HT-related dysfunctions, providing invaluable insights into both health and disease.

Concurrent processing of the prosodic hierarchy is supported by cortical entrainment and phase-amplitude coupling
Models of phonology posit a hierarchy of prosodic units that are relatively independent from syntactic structure, requiring its own parsing. Surprisingly, it remains unexplored how this prosodic hierarchy is represented in the brain. We investigated this foundational question by means of an EEG study. Thirty young adults listened to German sentences containing manipulations at different levels of the prosodic hierarchy. Evaluating speech-to-brain cortical entrainment and phase-amplitude coupling revealed that prosody's hierarchical structure is maintained at the neural level. The faithfulness of this tracking varied as a function of the hierarchy's degree of intactness as well as systematic inter-individual differences in audio-motor synchronization. The results underscore the role of complex oscillatory mechanisms in configuring the continuous and hierarchical nature of the speech signal and firmly situate prosody as a structure indispensable from theoretical perspectives on spoken language comprehension in the brain.

Investigation of neural functional connectivity in thick acute mouse brain slices with novel multi-region 3D neural probe arrays
There are significant limitations in investigating complex neural circuits in vivo, including drawbacks to midline-adjacent surgeries, limited accessibility to deep brain regions and number of feasible regional targets for simultaneous recordings, and analytical or experimental biases from recording one columnar plane. On the other hand, recording extracellular neural signals ex vivo or in vitro using planar microelectrode arrays (MEAs) only permits slice surface recordings, and since conventional slices under 400 m-thick or dissociated cultures are used, no experiments contain a physiological multi-region circuit, drastically limiting conclusions about connectivity and pharmacology. Using thick, tract-preserving acute brain slices to record otherwise unassailable neural circuits ex vivo combines the strengths of both types of experiments, but is assumed to precipitate ischemic injury due to oxygen scarcity within the slice. Here, we report the first application of custom, multi-region silicon neural probe arrays to record spontaneous activity & optogenetically-induced functional connectivity across the mesocorticolimbic pathway within tract-preserving 800 m sagittal mouse brain slices, compared with 400 m slices, among three brain regions: the ventral tegmental area (VTA), ventral striatum (VS), & medial prefrontal cortex (mPFC). We show that most single-unit signals are an order of magnitude below the noise floor seen using silicon probes in vivo, providing unit yields far higher than previously assumed, allowing for a deep functional understanding of acute slice condition compared to the assumed deterioration due to ischemia. Overall, our method allows for acute circuit manipulations beyond what is available in vivo, with far more information than conventional slice preparations.

Multivariate Time-Lagged Multidimensional Pattern Connectivity (mvTL-MDPC) for EEG/MEG Functional Connectivity Analysis
Multidimensional connectivity methods are critical to reveal the full pattern of complex interactions between brain regions over time. However, to date only bivariate multidimensional methods are available for time-resolved EEG/MEG data, which may overestimate connectivity due to the confounding effects of spurious and indirect dependencies. Here, we introduce a novel functional connectivity method which is both multivariate and multidimensional, Multivariate Time-lagged Multidimensional Pattern Connectivity (mvTL-MDPC), to address this issue in time-resolved EEG/MEG applications. This novel method extends its bivariate counterpart TL-MDPC to estimate how well patterns in an ROI 1 at time point t_1 can be linearly predicted from patterns of an ROI 2 at time point t_2 while partialling out the multivariate contributions from other brain regions. We compared the performance of mvTL-MDPC and TL-MDPC on simulated data designed to test their ability to identify true direct connections, using the Euclidean distance to the ground truth to measure goodness-of-fit. These simulations demonstrate that mvTL-MDPC produces more reliable and accurate results than the bivariate method. We therefore applied this method to an existing EEG/MEG dataset contrasting words presented in more or less demanding semantic tasks, to identify the dynamic brain network underlying controlled semantic cognition. As expected, mvTL-MDPC was more selective than TL-MDPC, identifying fewer connections, likely due to a reduction in the detection of spurious or indirect connections. Dynamic connections were identified between bilateral anterior temporal lobes, posterior temporal cortex and inferior frontal gyrus, in line with recent neuroscientific models of semantic cognition.

NeuroCSF: an fMRI method to measure contrast sensitivity function in human visual cortex
The contrast sensitivity function (CSF) describes a range of spatial frequencies (SF) that are detectable at a given level of contrast and is a very valuable tool both in clinical and fundamental research. However, despite its immense value, the full potential of the CSF has not been utilized in every aspect of clinical research due to time limits and patient factors. We propose neuroCSF as a new method for measuring the CSF across the visual field directly from brain activity, and with minimal demand from participants. NeuroCSF is a computational model that estimates voxel-wise CSF parameters (i.e., peak contrast sensitivity, peak spatial frequency, and spatial frequency bandwidth) from functional magnetic resonance imaging (fMRI) signals, under controlled visual stimulation conditions. The approach extends the population spatial frequency tuning (Aghajari, Vinke, & Ling, 2020) and population receptive field (Dumoulin & Wandell, 2008) methods to provide the first characterization of a full CSF using neuroimaging. We observe that across early visual areas (V1, V2 and V3), the CSF peak spatial frequency and spatial frequency cutoff are significantly higher for foveal eccentricity and decrease at parafoveal eccentricities. Conversely, SF bandwidth slowly increases with eccentricity, while peak contrast sensitivity remains constant with eccentricity for all early visual areas. Thus, cortical CSF estimates vary systematically with eccentricity. The neuroCSF approach opens new perspectives for the study of cortical visual functions in various disorders where the CSF is impacted, such as amblyopia, traumatic brain injury, and multiple sclerosis.

Age-related memory CD8 T cells induce and track Alzheimers-like neurodegeneration
Cerebral (A{beta}) plaque and (pTau) tangle deposition are hallmarks of Alzheimers disease (AD), yet are insufficient to confer complete AD-like neurodegeneration experimentally. Factors acting upstream of A{beta}/pTau in AD remain unknown, but their identification could enable earlier diagnosis and more effective treatments. T cell abnormalities are emerging AD hallmarks, and CD8 T cells were recently found to mediate neurodegeneration downstream of tangle deposition in hereditary neurodegeneration models. The precise impact of T cells downstream of A{beta}/fibrillar pTau, however, appears to vary depending on the animal model used. Our prior work suggested that antigen-specific memory CD8 T (hiT) cells act upstream of A{beta}/pTau after brain injury. Here we examine whether hiT cells influence sporadic AD-like pathophysiology upstream of A{beta}/pTau. Examining neuropathology, gene expression, and behavior in our hiT mouse model we show that CD8 T cells induce plaque and tangle-like deposition, modulate AD-related genes, and ultimately result in progressive neurodegeneration with both gross and fine features of sporadic human AD. T cells required Perforin to initiate this pathophysiology, and IFN{gamma} for most gene expression changes and progression to more widespread neurodegenerative disease. Analogous antigen-specific memory CD8 T cells were significantly elevated in the brains of human AD patients, and their loss from blood corresponded to sporadic AD and related cognitive decline better than plasma pTau-217, a promising AD biomarker candidate. Our work is the first to identify an age-related factor acting upstream of A{beta}/pTau to initiate AD-like pathophysiology, the mechanisms promoting its pathogenicity, and its relevance to human sporadic AD.

Condensin-mediated restriction of retrotransposable elements facilitates brain development in Drosophila melanogaster.
Neural stem and progenitor cell (NSPC) maintenance are essential for ensuring that organisms are born with proper brain volumes and head sizes. Microcephaly is a disorder in which babies are born with significantly smaller head sizes and cortical volumes. Mutations in subunits of the DNA organizing complexes, condensins have been identified in microcephaly patients. However the molecular mechanisms by which condensin insufficiency causes microcephaly remain elusive. We previously identified conserved roles for condensins in repression of retrotransposable elements (RTEs). Here, we show that condensin subunit knockdown in NSPCs of the Drosophila larval central brain increases RTE expression and mobility which causes cell death, and significantly decreases adult head sizes and brain volumes. These findings suggest that unrestricted RTE expression and activity may lead to improper brain development in condensin insufficient organisms, and lay the foundation for future exploration of causative roles for RTEs in other microcephaly models.

TDP-43 dysregulation of polyadenylation site selection is a defining feature of RNA misprocessing in ALS/FTD and related disorders
Nuclear clearance and cytoplasmic aggregation of the RNA-binding protein TDP-43 are observed in many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia(FTD). Although TDP-43 dysregulation of splicing has emerged as a key event in these diseases, TDP-43 can also regulate polyadenylation; yet, this has not been adequately studied. Here, we applied the dynamic analysis of polyadenylation from RNA-seq (DaPars) tool to ALS/FTD transcriptome datasets, and report extensive alternative polyadenylation (APA) upon TDP-43 alteration in ALS/FTD cell models and postmortem ALS/FTD neuronal nuclei. Importantly, many identified APA genes highlight pathways implicated in ALS/FTD pathogenesis. To determine the functional significance of APA elicited by TDP-43 nuclear depletion, we examined microtubule affinity regulating kinase 3 (MARK3). Nuclear loss of TDP-43 yielded increased expression of MARK3 transcripts with longer 3'UTRs, resulting in greater transcript stability and elevated MARK3 protein levels, which promotes increased neuronal tau S262 phosphorylation. Our findings define changes in polyadenylation site selection as a previously unrecognized feature of TDP-43-driven disease pathology in ALS/FTD and highlight a potentially novel mechanistic link between TDP-43 dysfunction and tau regulation.

Subthalamic nucleus activity modifications prior to clinical impairment in a progressive model of Parkinson's disease
Background: Parkinson's disease (PD) is clinically diagnosed based on motor impairments related to akinesia, rigidity, and tremor. These symptoms are delayed in the course of the disease and that contributes strongly to its late diagnosis. Cognitive and limbic symptoms may precede motor symptoms, thus opening an earlier diagnostic window, but their early kinetics need to be better characterized. Furthermore, despite adapted medications, these non-motor symptoms evolve and worsen over time. Surgical treatment with high frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN), whereas significantly improves motor symptoms, does not address specifically the non-motor symptoms. A better temporal characterization of the onset of non-motor symptoms combined with adapted parameters of stimulation of DBS could potentially optimize the surgical treatment. Objective: We aimed to correlate STN activity with the early phase of motor, cognitive, and limbic symptoms of PD and to propose specific STN-DBS paradigm of stimulation to take over all symptoms. Methods: Local field potentials of the STN were recorded in two non-human primates (Macaca fascicularis) while performing a behavioral task allowing the assessment of motor, cognitive, and limbic reward-related behavioral components. In parallel, a progressive model of PD, consisting in small injections of 1-methyl-4-phenyl-1,2,3,6-tetrhydropyridine (MPTP, 0.2-0.5mg/kg), was used to characterize behavior for several months until the appearance of motor symptoms. Finally, when a parkinsonian syndrome was well established and stable, behavioral effects of high- (HFS, 130Hz) and low- (LFS, 4Hz) frequency stimulations were investigated. Results After the first MPTP injections, we observed a gradual progression of the parkinsonian syndrome from stage 1 without any symptoms, to stage 3 with limbic, cognitive, and motor symptoms. In addition, each stage was associated with specific changes in STN electrophysiological activities. Stage 1, with no significant symptoms although MPTP intoxication has begun, was marked by a decrease in the power of reward-related gamma/theta oscillations. Stage 2 was characterized by an early decline in motivation and the appearance of decreased theta-band activity during decision-making. Later, an increase in error on Switch trials was reported, illustrating the stage 2', and a decrease in beta-gamma power after motor movement occurred. Finally, stage 3 was characterized by an increase in motor response time, while retaining all the STN neuronal changes. Conclusion: Our results suggest a progressive timeline in the onset of behavioral impairments with first limbic symptoms, followed by cognitive and then motor symptoms. Furthermore, specific electrophysiological biomarkers of each symptom are found early in the STN and can predict their onset and help to better understand their pathophysiology. Finally, we propose a combined stimulation with HFS in dorsal STN and LFS in ventral STN to optimize STN-DBS and reduce both motor and non-motor symptoms.

Alpha phase-coding supports feature binding during working memory maintenance
Working memory (WM) is the ability to retain and manipulate information in mind, which allows mnemonic representations to flexibly guide behavior. Successful WM requires that objects' individual features are bound into cohesive representations, however the mechanisms supporting feature binding remain unclear. Binding errors (or swaps) provide a window into the intrinsic limits in capacity of WM. We tested the hypothesis that binding in WM is accomplished via neural phase synchrony and swaps result from its perturbations. Using magnetoencephalography data collected from human subjects, in a task designed to induce swaps, we showed that swaps are characterized by reduced phase-locked oscillatory activity during memory retention. We found that this reduction arises from increased phase-coding variability in the alpha-band, over a distributed network of sensorimotor areas. Our findings support the notion that feature binding in WM is accomplished through phase-coding dynamics that emerge from the competition between different memories.

Activity-Dependent Ectopic Spiking in Parvalbumin-Expressing Interneurons of the Neocortex
Canonically, action potentials of most mammalian neurons initiate at the axon initial segment and propagate bidirectionally: orthodromically along the distal axon, and retrogradely into the soma and dendrites. Under some circumstances action potentials may initiate ectopically, at sites distal to the axon initial segment, and propagate antidromically along the axon. These ectopic action potentials (EAPs) have been observed in experimental models of seizures and chronic pain, and more rarely in nonpathological forebrain neurons. Here we report that a large majority of parvalbumin-expressing (PV+) interneurons in upper layers of mouse neocortex, from both orbitofrontal and primary somatosensory areas, fire EAPs after sufficient activation of their somata. Somatostatin-expressing interneurons also fire EAPs, though less robustly. Ectopic firing in PV+ cells occurs in varying temporal patterns and can persist for several seconds. PV+ cells evoke strong synaptic inhibition in pyramidal neurons and interneurons and play critical roles in cortical function. Our results suggest that ectopic spiking of PV+ interneurons is common, and may contribute to both normal and pathological network functions of the neocortex.

Maternal n-3 enriched diet reprograms neurovascular transcriptome and blunts inflammation in neonate
Infection during perinatal period can adversely affect brain development, predispose infants to ischemic stroke and have lifelong consequences. We previously demonstrated that diet enriched in n-3 polyunsaturated fatty acids (PUFA) transforms brain lipid composition and protects from neonatal stroke. Vasculature is a critical interface between blood and brain providing a barrier to systemic infection. Here we examined whether maternal PUFA-enriched diets exert reprograming of endothelial cell signalling in 9-day old mice after endotoxin (LPS)-induced infection. Transcriptome analysis was performed on brain microvessels from pups born to dams maintained on 3 diets: standard, n-3 or n-6 enriched. N-3 diet enabled higher immune reactivity in brain vasculature, while preventing imbalance of cell cycle regulation and extracellular matrix cascades that accompanied inflammatory response in standard diet. LPS response in blood and brain was blunted in n-3 offspring. Cerebral angioarchitecture analysis revealed modified vessel complexity after LPS. Thus, n-3-enriched maternal diet partially prevents imbalance in homeostatic processes and alters inflammation rather than affects brain vascularization during early life. Importantly, maternal diet may presage offspring neurovascular outcomes later in life.

Dynamic transient brain states in preschoolers mirror parental report of behavior and emotion regulation
The temporal dynamics of resting-state networks (RSNs) may represent an intrinsic functional repertoire supporting cognitive control performance across the lifespan (Kupis et al., 2021). However, little is known about brain dynamics during the preschool period, which is a sensitive time window for cognitive control development. The fast timescale of synchronization and switching characterizing cortical network functional organization gives rise to quasi-stable patterns (i.e., brain states) that recur over time. These can be inferred at the whole-brain level using Hidden Markov Models (HMMs), an unsupervised machine learning technique that allows the identification of rapid oscillatory patterns at the macro-scale of cortical networks (Vidaurre et al., 2018). The present study used a HMM technique to investigate dynamic neural reconfigurations and their associations with behavioral (i.e., parental questionnaires) and cognitive (i.e., neuropsychological tests) measures in typically developing preschoolers (4-6 years old). We used high density EEG to better capture the fast reconfiguration patterns of the HMM-derived metrics (i.e., switching rates, entropy rates, transition probabilities and fractional occupancies). Our results revealed that the HMM-derived metrics were reliable indices of individual neural variability and differed between boys and girls. However, only brain state transition patterns toward prefrontal and default-mode brain states, predicted differences on parental-report questionnaire scores. Overall, these findings support the importance of resting-state brain dynamics as functional scaffolds for behavior and cognition. Brain state transitions may be crucial markers of individual differences in cognitive control development in preschoolers.

Developmental emergence of first- and higher-order thalamic neuron molecular identities
The thalamus is organized into nuclei that have distinct input and output connectivities with the cortex. While first-order (FO) nuclei - also called core nuclei - relay input from sensory organs on the body surface and project to primary cortical sensory areas, higher-order (HO) nuclei - matrix nuclei - instead receive their driver input from the cortex and project to secondary and associative areas within cortico-thalamo-cortical loops. Input-dependent processes have been shown to play a critical role in the emergence of FO thalamic neuron identity from a ground state HO neuron identity, yet how this identity emerges during development remains unknown. Here, using single-cell RNA sequencing of the developing embryonic thalamus, we show that FO thalamic identity emerges after HO identity and that peripheral input is critical for the maturation of excitatory, but not inhibitory FO-type neurons. Our findings reveal that subsets of HO neurons are developmentally co-opted into FO-type neurons, providing a mechanistic framework for the diversification of thalamic neuron types during development and evolution.

Disrupting fzd9b in zebrafish recapitulates stress- and anxiety-like behaviours associated with Williams syndrome
Williams syndrome (WS) is a multifaceted developmental disorder characterized by a spectrum of physical and intellectual traits. Individuals with WS exhibit friendly, impulsive, and hyper-social behaviours, often coupled with anxiety. WS is attributed to a microdeletion on chromosome 7q11.23, affecting several genes, including FZD9, which plays an important role in neurodevelopment. Thus, we postulated that disruptions in FZD9 might contribute to the behavioural features of WS including anxiety, and that pharmacological interventions targeting Wnt signalling, particularly the canonical pathway, might hold therapeutic potential for WS and related conditions. To test our hypothesis, we generated two mutant zebrafish lines with fzd9b disruptions. Our behavioural analysis revealed significant differences in stress- and anxiety-related responses at both larval and adult stages. Our attempt to restore stress reactivity by manipulating the Wnt/beta-catenin pathway using a GSK-3 inhibitor was unsuccessful. Our qPCR data indicated a compensatory mechanism involving the upregulation of fzd9b, wnt5b, and tafa5l genes, potentially contributing to the observed phenotypes. These findings highlight the role of Fzd9b in modulating anxiety responses in zebrafish, offering potential avenues for novel therapeutics to address the neurological features of WS and related disorders.

Neuronal Network Dynamics in the Posterodorsal Amygdala: Shaping Reproductive Hormone Pulsatility
Normal reproductive function and fertility rely on the rhythmic secretion of gonadotropin-releasing hormone (GnRH), which is driven by the hypothalamic GnRH pulse generator. A key regulator of the GnRH pulse generator is the posterodorsal subnucleus of the medial amygdala (MePD), a brain region involved in processing external environmental cues, including the effect of stress. However, the neuronal pathways enabling the modulation of GnRH secretion remain largely unknown. Here, we employ in silico modelling in order to explore the impact of dynamic inputs on GnRH pulse generator activity. We develop and analyse a mathematical model representing MePD neuronal circuits composed of GABAergic and glutamatergic neuronal populations, integrating it with our GnRH pulse generator model. Our analysis dissects the influence of excitatory and inhibitory MePD outputs on the GnRH pulse generator's activity and reveals a functionally relevant MePD glutamatergic projection to the GnRH pulse generator, which we probe with in vivo optogenetics.

Physical Effort Pre-Crastination Determines Preference in an Isometric Task
How the brain decides when to invest effort is a central question in neuroscience. When asked to walk a mile to a destination, would you choose a path with a hill at the beginning or the end? The traditional view of effort suggests we should be indifferent-all joules are equal so long as it does not interfere with accomplishing the goal. Yet when total joules are equal, the brain's sensitivity to the temporal profile of effort investment throughout a movement remains poorly understood. Here, we sought to parse out the interaction of time and physical effort by comparing subjective preferences in an isometric arm-pushing task that varied the duration and timing of high and low effort. Subjects were presented with a series of two-alternative forced choices, where they chose the force profile they would rather complete. Subjects preferred to pre-crastinate physical effort but were idiosyncratic about preference for task timing. A model of subjective utility that includes physical effort costs, task costs, and independent temporal sensitivity factors described subject preferences best. Interestingly, deliberation time and response vigor are best described by the same subjective utility model that won for preference, further validating this model of subjective utility. These results suggest physical effort costs are temporally sensitive, with earlier investment of effort preferred to later investment. These findings demonstrate that the representation of effort is based not only on the total energy required but its timing as well, and offer an alternative hypothesis for why animals pre-crastinate in physical tasks.

First-night effect reduces the beneficial effects of sleep on visual plasticity and modifies the underlying neurochemical processes
Individuals experience difficulty falling asleep in a new environment, termed the first night effect (FNE). However, the impact of the FNE on sleep-induced brain plasticity remains unclear. Here, using a within-subject design, we found that the FNE significantly reduces visual plasticity during sleep in young adults. Sleep-onset latency (SOL), an indicator of the FNE, was significantly longer during the first sleep session than the second session, confirming the FNE. We assessed performance gains in visual perceptual learning after sleep and increases in the excitatory-to-inhibitory neurotransmitter (E/I) ratio in early visual areas during sleep using magnetic resonance spectroscopy and polysomnography. These parameters were significantly smaller in sleep with the FNE than in sleep without the FNE; however, these parameters were not correlated with SOL. These results suggest that while the neural mechanisms of the FNE and brain plasticity are independent, sleep disturbances temporarily block the neurochemical process fundamental for brain plasticity.

Lipid Dysregulation Unveil the Intricate Interplay of Lysosomal and Mitochondrial Changes in Frontotemporal Dementia with GRN Haploinsufficiency
This study investigates the cellular pathology resulting from haploinsufficiency of progranulin (PGRN) in frontotemporal dementia (FTD) associated with granulin (GRN) mutations. Utilizing fibroblasts from FTD patients carrying a distinctive GRN mutation (c.709-1G>A), we observed lysosomal and lipofuscin accumulation, impaired lysosomal function, compromised autophagic flux, and mitochondrial abnormalities. Notably, recombinant human progranulin (rhPGRN) treatment restored lysosomal acidification, mitigated mitochondrial defects, and demonstrated beneficial effects. FTD-GRN fibroblasts exhibited abnormal lipid metabolism with increased lipid droplet formation, influenced by GRN haploinsufficiency and modulated by rhPGRN. Under nutrient-rich conditions, lipid droplet dynamics were shaped by autophagy and mitochondrial processes, potentially due to impaired fatty acid oxidation. These findings highlight a direct association between GRN deficiency and altered lysosomal-mitochondrial interactions, influencing lipid metabolism and contributing to FTD pathogenesis. The documented lysosomal dysfunction, impaired autophagy, mitochondrial anomalies, and altered lipid metabolism collectively suggest a complex interplay of cellular processes in the development of FTD-GRN.

Impact of dendritic spine loss on excitability of hippocampal CA1 pyramidal neurons: a computational study of early Alzheimer disease
Synaptic spine loss is an early pathophysiologic hallmark of Alzheimer disease (AD) that precedes overt loss of dendritic architecture and frank neurodegeneration. While spine loss signifies a decreased engagement of postsynaptic neurons by presynaptic targets, the degree to which loss of spines and their passive components impacts the excitability of postsynaptic neurons and responses to surviving synaptic inputs is unclear. Using passive multicompartmental models of CA1 pyramidal neurons (PNs), implicated in early AD, we find that spine loss alone drives a boosting of remaining inputs to their proximal and distal dendrites, targeted by CA3 and entorhinal cortex (EC), respectively. This boosting effect is higher in distal versus proximal dendrites and can be mediated by spine loss restricted to the distal compartment, enough to impact synaptic input integration and somatodendritic backpropagation. This has particular relevance to very early stages of AD in which pathophysiology extends from EC to CA1.

Transcranial Focused Ultrasound Remotely Modulates Extrastriate Visual Cortex with Subregion Specificity
Low-intensity transcranial focused ultrasound (tFUS) has emerged as a powerful neuromodulation tool characterized by its deep penetration and precise spatial targeting to influence neural activity. Our study directed low-intensity tFUS stimulation onto a region of prefrontal cortex (the frontal eye field, or FEF) of a rhesus macaque to examine its impact on a remote site, the extrastriate visual cortex (area V4). This pair of cortical regions form a top-down modulatory circuit that has been studied extensively with electrical microstimulation. To measure the impact of tFUS stimulation, we recorded local field potentials (LFPs) and multi-unit spiking activities from a multi-electrode array implanted in the visual cortex. To deliver tFUS stimulation, we leveraged a customized 128-element random array ultrasound transducer with improved spatial targeting. We observed that tFUS stimulation in FEF produced modulation of V4 neuronal activity, either through enhancement or suppression, dependent on the pulse repetition frequency of the tFUS stimulation. Electronically steering the transcranial ultrasound focus through the targeted FEF cortical region produced changes in the level of modulation, indicating that the tFUS stimulation was spatially targeted within FEF. Modulation of V4 activity was confined to specific frequency bands, and this modulation was dependent on the presence or absence of a visual stimulus during tFUS stimulation. A control study targeting the insula produced no effect, emphasizing the region-specific nature of tFUS neuromodulation. Our findings shed light on the capacity of tFUS to modulate specific neural pathways and provide a comprehensive understanding of its potential applications for neuromodulation within brain networks.

Narcissus reflected: gray and white matter features joint contribution to the default mode network in predicting narcissistic personality traits
Despite the clinical significance of narcissistic personality, its neural bases have not been clear yet, primarily due to methodological limitations of the previous studies, such as the low sample size, the use of univariate techniques and the focus on only one brain modality. In this study, we employed for the first time a combination of unsupervised and supervised machine learning methods, to identify the joint contributions of gray (GM) and white matter (WM) to narcissistic personality traits (NPT). After preprocessing, the brain scans of 135 participants were decomposed into eight independent networks of covarying GM and WM via Parallel ICA. Subsequently, stepwise regression and Random Forest were used to predict NPT. We hypothesize that a fronto-temporo parietal network mainly related to the Default Mode Network, may be involved in NPT and white matter regions related to these regions. Results demonstrated a distributed network that included GM alterations in fronto-temporal regions, the insula, and the cingulate cortex, along with WM alterations in cerebellar and thalamic regions. To assess the specificity of our findings, we also examined whether the brain network predicting narcissism could predict other personality traits (i.e., Histrionic, Paranoid, and Avoidant personalities). Notably, this network did not predict these personality traits. Additionally, a supervised machine learning model (Random Forest) was used to extract a predictive model to generalize to new cases. Results confirmed that the same network could predict new cases. These findings hold promise for advancing our understanding of personality traits and potentially uncovering brain biomarkers associated with narcissism.

Brain resident macrophages regulate sleep, with repopulated ones being unable to reestablish the original sleep circuits
Brain resident macrophages such as microglia and CNS-associated macrophages (CAMs) are already established before birth and play therefore a crucial role for normal brain functioning during development. However, their involvement in fine-tuning complex physiological functions such as vigilance states (VS) after birth remains poorly understood. Here, we investigated the reciprocal interaction of microglia and VS using multimodal high throughput transcriptional, electrophysiological and metabolomic profiling in mice. We found that sleep deprivation caused severe transcriptional changes in microglia and CAMs and absence of the wake-promoting neuropeptides hypocretin/orexin intensified these effects. Depletion of embryonic microglia robustly increased sleep quantity during the active period, while decreased sleep quality that was reflected in reduced power of brain sleep oscillations. Unexpectedly, subsequent repopulation by postnatal microglia failed to reestablish normal sleep-wake patterns, and even induced additional abnormalities such as sleep fragmentation. Moreover, we found a substantial excitatory-inhibitory synaptic imbalance following microglia depletion, which was not normalized after microglial repopulation and even lead to an increase of inhibitory synapses in the brain. At the metabolite level, we observed a distinct metabolite pattern after microglia depletion, which largely returned to normal levels after repopulation. Our findings suggest a so far largely unknown interaction between microglia and brain VS and emphasizes striking functional differences between embryonic and postnatal-derived microglia, thereby potentially paving the way for the further exploration of microglia of different origin and their roles in sleep disorders and synaptic connectivity.

IMPDH2 filaments protect from neurodegeneration in AMPD2 deficiency
Metabolic dysregulation is one of the most common causes of pediatric neurodegenerative disorders. However, how the disruption of ubiquitous and essential metabolic pathways predominantly affect neural tissue remains unclear. Here we use mouse models of AMPD2 deficiency to study cellular and molecular mechanisms that lead to selective neuronal vulnerability to purine metabolism imbalance. We show that AMPD deficiency in mice primarily leads to hippocampal dentate gyrus degeneration despite causing a generalized reduction of brain GTP levels. Remarkably, we found that neurodegeneration resistant regions accumulate micron sized filaments of IMPDH2, the rate limiting enzyme in GTP synthesis. In contrast, IMPDH2 filaments are barely detectable in the hippocampal dentate gyrus, which shows a progressive neuroinflammation and neurodegeneration. Furthermore, using a human AMPD2 deficient neural cell culture model, we show that blocking IMPDH2 polymerization with a dominant negative IMPDH2 variant, impairs AMPD2 deficient neural progenitor growth. Together, our findings suggest that IMPDH2 polymerization prevents detrimental GTP deprivation in neurons with available GTP precursor molecules, providing resistance to neurodegeneration. Our findings open the possibility of exploring the involvement of IMPDH2 assembly as a therapeutic intervention for neurodegeneration.

Infralimbic activity during REM sleep facilitates fear extinction memory
Rapid eye movement (REM) sleep is known to facilitate fear extinction and play a protective role against fearful memories. Consequently, disruption of REM sleep after a traumatic event may increase the risk for developing PTSD. However, the underlying mechanisms by which REM sleep promotes extinction of aversive memories remain largely unknown. The infralimbic cortex (IL) is a key brain structure for the consolidation of extinction memory. Using calcium imaging, we found in mice that most IL pyramidal neurons are intensively activated during REM sleep. Optogenetically suppressing the IL activity during REM sleep within a 4-hour window after auditory-cued fear conditioning impaired extinction memory consolidation. In contrast, REM-specific inhibition of the IL cortex after extinction learning did not affect the extinction memory. Whole-cell patch-clamp recordings demonstrated that inactivating IL neurons during REM sleep depresses their excitability. Together, our findings demonstrate that REM sleep after fear conditioning facilitates fear extinction by enhancing IL excitability, and highlight the importance of REM sleep in the aftermath of traumatic events for protecting against traumatic memories.

Development of blood-cerebrospinal fluid barrier model expressing pharmaceutically important transporters.
We have established and optimized a protocol for the high-yield isolation of primary epithelial cells from rat choroid plexus. The addition of cytosine arabinoside suppressed the growth of contaminating cells, and epithelial culture was grown into a confluent impermeable monolayer within 5-6 days after seeding. To form an in vitro blood-CSF barrier, epithelial cells were plated on inverted coated polycarbonate support of Transwell inserts. Morphologically, the polarized cells remained cuboidal in shape and expressed TJ proteins at a high rate. The filter-grown monolayers displayed transendothelial resistance (TEER) values in the range of 160 to 180 Ohm x cm2 and remained at this level for 3 days, indicating the persistent formation of continuous TJs. The cells were able to secrete cerebrospinal fluid (CSF) actively. Epithelial cells showed expression of selective influx and efflux transporters. To conclude, our BCSFB model exhibits tight, functional barrier characteristics and shows the functional expression of the pharmaceutically important influx/efflux transporters. The recent model is suitable for in vitro investigations of BCSFB and routine pre-clinical drug discovery.

A dynamic functional connectivity toolbox for multiverse analysis
Various methods for estimating dynamic functional connectivity from fMRI data and subsequent analyses through graph theoretic approaches have been introduced in recent years. But with many of the ground truths unknown, researchers are often faced with arbitrary yet defensible decisions for their analyses, which raises concerns about the reproducibility of results. We here aim to address this issue through the implementation of a wide array of dynamic functional connectivity methods in a unified Python software package, facilitating a diverse exploration of brain dynamics. Anchored in the framework of multiverse analysis, the present work further introduces a workflow for the systematic examination of various methodological decisions. The developed toolbox is supplemented by a graphical user interface for easy usability and accessibility if usage outside of a script-based Python analysis pipeline is desired. Further, extensive demo scripts are provided for researchers to easily adapt this approach for their own analyses.

Resilience to Early Life Adversity Effects on Stress Reactivity by Postnatal Knockdown of 5-HT1A Autoreceptors
Early Life Adversity (ELA) predisposes to stress hypersensitivity in adulthood, but neurobiological mechanisms that can protect from long-lasting effects of ELA are poorly understood. Serotonin 1A (5HT1A) autoreceptors in the raphe nuclei regulate adult stress vulnerability, but if 5HT1A could be targeted to prevent ELA effects on susceptibility to future stressors is unknown. Here, we exposed mice with postnatal knockdown of 5HT1A autoreceptors to the limited bedding and nesting model of ELA from postnatal day (P)3-10. We then tested behavioral, neuroendocrine, neurogenic, and neuroinflammatory responses to an acute swim stress in male and female mice in adolescence (P35) and in adulthood (P56). In ELA-exposed females, adult swim stress exposure increased passive coping and despair-like behavior, corticosterone levels at baseline and after stress, and neuronal activity and corticotropin releasing hormone levels in the paraventricular nucleus of the hypothalamus. ELA also reduced neurogenesis and increased microglia activation in the ventral dentate gyrus (DG) of the hippocampus - an important mediator of individual differences in stress susceptibility. These effects of ELA were specific to females, but not males, and manifested predominantly in adulthood, but not earlier on in adolescence. Postnatal 5HT1A autoreceptor knockdown prevented ELA effects on stress reactivity and on neurogenesis and neuroinflammation in the DG, indicating that reducing 5HT1A autoreceptors confers resilience to ELA. Our findings demonstrate that ELA induces long-lasting and sex-specific impairments in stress reactivity and ventral DG function across development, and identify 5HT1A autoreceptors as potential targets to prevent these persistent effects of ELA.

Learned response dynamics reflect stimulus timing and encode temporal expectation violations in superficial layers of mouse V1
The ability to recognize ordered event sequences is a fundamental component of sensory cognition and underlies the capacity to generate temporally specific expectations of future events based on previous experience. Various lines of evidence suggest that the primary visual cortex participates in some form of predictive processing, but many details remain ambiguous. Here we use two-photon calcium imaging in layer 2/3 of the mouse primary visual cortex (V1) to study changes to neural activity under a multi-day sequence learning paradigm with respect to prediction error responses, stimulus encoding, and time. We find increased neural activity at the time an expected, but omitted, stimulus would have occurred but no significant prediction error responses following an unexpected stimulus substitution. Sequence representations became sparser and less correlated with training, although these changes had no effect on decoding accuracy of stimulus identity or timing. Additionally, we find that experience modifies the temporal structure of stimulus responses to produce a bias towards predictive stimulus-locked activity. Finally, we find significant temporal structure during intersequence rest periods that was largely unchanged by training.

Comparison of histological procedures and antigenicity of human post-mortem brains fixed with solutions used in gross anatomy laboratories
Background: Brain banks provide small tissue samples to researchers, while gross anatomy laboratories could provide larger samples, including complete brains to neuroscientists. However, they are preserved with solutions appropriate for gross-dissection, different from the classic neutral-buffered formalin (NBF) used in brain banks. Our previous work in mice showed that two gross-anatomy laboratory solutions, a saturated-salt-solution (SSS) and an alcohol-formaldehyde-solution (AFS), preserve antigenicity of the main cellular markers. Our goal is now to compare the quality of histology and antigenicity preservation of human brains fixed with NBF by immersion (practice of brain banks) vs. those fixed with a SSS and an AFS by whole body perfusion, practice of gross-anatomy laboratories. Methods: We used a convenience sample of 42 brains (31 males, 11 females; 25-90 years old) fixed with NBF (N=12), SSS (N=13), and AFS (N=17). One cm3 tissue blocks were cut, cryoprotected, frozen and sliced into 40 um sections. The four cell populations were labeled using immunohistochemistry (neuronal-nuclei (NeuN), glial-fibrillary-acidic-protein (GFAP), ionized-calcium-binding-adaptor-molecule1 (Iba1) and myelin-proteolipid-protein (PLP)). We qualitatively assessed antigenicity and cell distribution, and compared the ease of manipulation of the sections, the microscopic tissue quality, and the quality of common histochemical stains (e.g., Cresyl violet, Luxol fast blue, etc.) across solutions. Results: Sections of SSS-fixed brains were more difficult to manipulate and showed poorer tissue quality than those from brains fixed with the other solutions. The four antigens were preserved, and cell labeling was more often homogenous in AFS-fixed specimens. NeuN and GFAP were not always present in the NBF and SSS samples. Some antigens were heterogeneously distributed in some specimens, independently of the fixative, but an antigen retrieval protocol successfully recovered them. Finally, the histochemical stains were of sufficient quality regardless of the fixative, although neurons were more often paler in SSS-fixed specimens. Conclusion: Antigenicity was preserved in human brains fixed with solutions used in human gross-anatomy (albeit the poorer quality of SSS-fixed specimens). For some specific variables, histology quality was superior in AFS-fixed brains. Furthermore, we show the feasibility of frequently used histochemical stains. These results are promising for neuroscientists interested in using brain specimens from anatomy laboratories.

Dimensions of early life adversity are differentially associated with patterns of delayed and accelerated brain maturation
Different types of early-life adversity have been associated with childrens brain structure and function. However, understanding the disparate influence of distinct adversity exposures on the developing brain remains a major challenge. This study investigates the neural correlates of 10 robust dimensions of early-life adversity identified through exploratory factor analysis in a large community sample of youth from the Adolescent Brain Cognitive Development (ABCD) Study. Brain age models were trained, validated, and tested separately on T1- weighted (T1; N = 9524), diffusion tensor (DTI; N = 8834), and resting-state functional (rs- fMRI; N = 8233) magnetic resonance imaging (MRI) data from two time points (mean age = 10.7 years, SD = 1.2, range = 8.9-13.8 years). Bayesian multilevel modelling supported distinct associations between different types of early-life adversity exposures and younger- and older-looking brains. Dimensions generally related to emotional neglect, such as lack of primary and secondary caregiver support, and lack of caregiver supervision, were associated with lower brain age gaps (BAGs), i.e., younger-looking brains. In contrast, dimensions generally related to caregiver psychopathology, trauma exposure, family aggression, substance use and separation from biological parent, and socio-economic disadvantage and neighbourhood safety were associated with higher BAGs, i.e., older-looking brains. The findings suggest that dimensions of early-life adversity are differentially associated with distinct neurodevelopmental patterns, indicative of dimension-specific delayed and accelerated brain maturation.

Tau-related reduction of glucose metabolism in mild cognitive impairment occurs independently of APOE ε4 genotype and is gradually modulated by β amyloid
Background: PET imaging studies have shown that spatially distributed measurements of {beta}-amyloid are significantly correlated with glucose metabolism in Mild Cognitive Impairment (MCI) independently of the APOE {varepsilon}4 genotype. In contrast, the relationship between tau and glucose metabolism at different stages of Alzheimer's Disease (AD) has not been fully understood. Objective: We hypothesize that spatially distributed scores of tau PET are associated with an even stronger reduction of glucose metabolism, independent of the APOE {varepsilon}4 genotype and gradually modulated by {beta}-amyloid. Methods: We applied a cross-sectional statistical analysis to concurrent [18F]flortaucipir PET, [18F]florbetapir PET, and 2-[18F]fluoro-2-deoxyglucose (FDG) PET images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study. We employed a Singular Value Decomposition (SVD) approach to the cross-correlation matrix between tau and the FDG images, as well as between tau and {beta}-amyloid PET images. The resulting SVD-based tau scores are associated with cortical regions where a reduced glucose metabolism is maximally correlated with distributed patterns of tau, accounting for the effect of spatially distributed {beta}-amyloid. Results: From a population of MCI subjects, we found that the SVD-based tau scores had their maximal spatial representation within the entorhinal cortex and the lateral inferior temporal gyrus, and were significantly correlated with glucose metabolism in several cortical regions, independently from the confounding effect of the {beta}-amyloid scores and APOE {varepsilon}4. Moreover, {beta}-amyloid gradually modulated the association between tau and glucose metabolism. Conclusions: Our approach uncovered spatially distributed patterns of the tau-glucose metabolism relationship after accounting for the {beta}-amyloid effects. We showed that the SVD-based tau scores have a strong relationship with decreasing glucose metabolism. By highlighting the more significant role of tau, rather than {beta}-amyloid, on the reduction of glucose metabolism, our results could have important consequences in the therapeutic treatment of AD.

fNIRS Dataset During Complex Scene Analysis
When analyzing complex scenes, humans often focus their attention on an object at a particular spatial location. The ability to decode the attended spatial location would facilitate brain computer interfaces for complex scene analysis (CSA). Here, we investigated capability of functional near-infrared spectroscopy (fNIRS) to decode audio-visual spatial attention in the presence of competing stimuli from multiple locations. We targeted dorsal frontoparietal network including frontal eye field (FEF) and intra-parietal sulcus (IPS) as well as superior temporal gyrus/planum temporal (STG/PT). They all were shown in previous functional magnetic resonance imaging (fMRI) studies to be activated by auditory, visual, or audio-visual spatial tasks. To date, fNIRS has not been applied to decode auditory and visual-spatial attention during CSA, and thus, no such dataset exists yet. This report provides an open-access fNIRS dataset that can be used to develop, test, and compare machine learning algorithms for classifying attended locations based on the fNIRS signals on a single trial basis.

Taste cells expressing Ionotropic Receptor 94e reciprocally impact feeding and egg laying in Drosophila
Chemosensory cells across the body of Drosophila melanogaster evaluate the environment and play a crucial role in neural circuits that prioritize feeding, mating, or egg laying. Previous mapping of gustatory receptor neurons (GRNs) on the fly labellum identified a set of neurons in L-type sensilla defined by expression of Ionotropic Receptor 94e (IR94e), but the impact of IR94e GRNs on behavior remained unclear. To understand their behavioral output, we used optogenetics and chemogenetics to activate IR94e neurons and found that they drive mild suppression of feeding but enhanced egg laying. In vivo calcium imaging revealed that IR94e GRNs respond strongly to certain amino acids, including glutamate. Furthermore, we found that IR94e is necessary and sufficient for the detection of amino acid ligands, and co-receptors IR25a and IR76b are also required for IR94e GRN activation. Finally, IR94e mutants show behavioral changes to solutions containing amino acids, including increased consumption and decreased egg laying. Overall, our results suggest that IR94e GRNs on the fly labellum discourage feeding and encourage egg laying as part of an important behavioral switch in response to certain chemical cues.

Standardised Measurements for Monitoring and Comparing Multiphoton Microscope Systems
The goal of this protocol is to enable better characterisation of multiphoton microscopy hardware across a large user base. The scope of this protocol is purposefully limited to focus on hardware, touching on software and data analysis routines only where relevant. The intended audiences are scientists using and building multiphoton microscopes in their laboratories. The goal is that any scientist, not only those with optical expertise, can test whether their multiphoton microscope is performing well and producing consistent data over the lifetime of their system.

Sensory Input, Sex, and Function Shape Hypothalamic Cell Type Development
Mammalian behavior and physiology undergo dramatic changes in early life. Young animals rely on conspecifics to meet their homeostatic needs, until weaning and puberty initiate nutritional independence and sex-specific social interactions, respectively. How neuronal populations regulating homeostatic functions and social behaviors develop and mature during these transitions remains unclear. We used paired transcriptomic and chromatin accessibility profiling to examine the developmental trajectories of neuronal populations in the hypothalamic preoptic region, where cell types with key roles in physiological and behavioral control have been identified. These data reveal a remarkable diversity of developmental trajectories shaped by the sex of the animal, and the location and behavioral or physiological function of the corresponding cell types. We identify key stages of preoptic development, including the perinatal emergence of sex differences, postnatal maturation and subsequent refinement of signaling networks, and nonlinear transcriptional changes accelerating at the time of weaning and puberty. We assessed preoptic development in various sensory mutants and find a major role for vomeronasal sensing in the timing of preoptic cell type maturation. These results provide novel insights into the development of neurons controlling homeostatic functions and social behaviors and lay ground for examining the dynamics of these functions in early life.

Embryonic origins of forebrain oligodendrocytes revisited by combinatorial genetic fate mapping
Multiple embryonic origins give rise to forebrain oligodendrocytes (OLs), yet controversies and uncertainty exist regarding their differential contributions. We established intersectional and subtractional strategies to genetically fate map OLs produced by medial ganglionic eminence/preoptic area (MGE/POA), lateral/caudal ganglionic eminences (LGE/CGE) and dorsal pallium. We found that, contrary to the canonical view, LGE/CGE-derived OLs make minimum contributions to the neocortex and corpus callosum, but dominate piriform cortex and anterior commissure. Additionally, MGE/POA-derived OLs, instead of being entirely eliminated, make small but sustained contribution to cortex with a distribution pattern distinctive from those derived from the dorsal origin. Our study provides a revised and more comprehensive view of cortical and white matter OL origins, and established valuable new tools and strategies for future OL studies.

Exploring social modulation: Microglia as a key mediator of individual immune response, plasticity and pathology in App-NL-G-F mouse model of Alzheimer's disease
This study explores the influence of lifestyle on Alzheimer's disease (AD) progression using App-NL-G-F mice in a complex enrichment system. Mice exhibited social deficits before plaque pathology or memory impairment, revealing a crucial link between lifestyle, behavior, and neuroinflammation. Plasma analysis indicates early inflammation and apoptosis-related changes, setting the stage for identifying markers predicting plaque manifestation. Beyond pathology, social behavior is linked to adult neurogenesis and microglia coverage, forming a dynamic connection with microglia activation. Further, sc-RNA sequencing unveiled a decrease in interferon-responsive microglia and alteration in antigen processing with enrichment. These findings underscore the beneficial impact of social housing on microglia and interconnected factors, pointing to microglia as a critical mediator of the behavior-pathology- plasticity interplay in AD. The study enhances our understanding of AD complexity and offers insights into potential therapeutic strategies, emphasizing the multifaceted nature of AD progression and the role of lifestyle in shaping its course.

Chronic potentiation of metabotropic glutamate receptor 2 with a nanobody accelerates amyloidogenesis in Alzheimer's disease.
Immunotherapy of Alzheimer's disease (AD) is a promising approach to reduce the accumulation of amyloid-beta (A{beta}), a critical event in the onset of the disease. Targeting the group II metabotropic glutamate receptors, mGlu2 and mGlu3, could be important in controlling A{beta} production, although their respective contribution remains unclear due to the lack of selective tools. Here, we show that enhancing mGlu2 receptor activity increases A{beta}1-42 peptide production whereas activation of mGlu3 has no effect. We show that such a difference likely results from the direct interaction of APP with mGlu3, but not with mGlu2 receptors, that prevents APP amyloidogenic cleavage and A{beta}1-42 peptides production. We then show that chronic treatments of the AD model 5xFAD mice with a brain-penetrating mGlu2-potentiating nanobody accelerated amyloid aggregation and exacerbated memory deficits, but had no effect in control mice. Our results confirm that a selective mGluR2 activation exacerbates AD disease development, suggesting that therapeutic benefices could be obtained with blockers of this receptor. Our study also provides the proof-of-concept that chronic administration of nanobodies targeting neuroreceptors can be envisioned to treat brain diseases.

Targeting resident astrocytes attenuates neuropathic pain after spinal cord injury
Astrocytes derive from different lineages and play a critical role in neuropathic pain after spinal cord injury (SCI). Whether selective eliminating these main origins of astrocytes in lumbar enlargement could attenuate SCI-induced neuropathic pain remains unclear. In this study, astrocytes in lumbar enlargement were lineage traced, targeted and selectively eliminated through transgenic mice injected with an adeno-associated virus vector and diphtheria toxin. Pain-related behaviors were measured with an electronic von Frey apparatus and a cold/hot plate after SCI. RNA sequencing, bioinformatics analysis, molecular experiment and immunohistochemistry were used to explore the potential mechanisms after astrocyte elimination. Through lineage tracing, we concluded the resident astrocytes but not ependymal cells were the main origins of astrocytes-induced neuropathic pain. SCI induced mice to obtain significant pain symptoms and astrocyte activation in lumbar enlargement. Selective resident astrocytes elimination in lumbar enlargement could attenuate neuropathic pain and activate microglia. Interestingly, the type I interferons (IFNs) signal was significantly activated after astrocytes elimination, and the most activated Gene Ontology terms and pathways were associated with the type I IFNs signal which was mainly activated in microglia and further verified in vitro and in vivo. Furthermore, different concentrations of interferon and Stimulator of interferon genes (STING) agonist could activate the type I IFNs signal in microglia. Our results elucidate that selectively eliminating resident astrocytes attenuated neuropathic pain associated with type I IFNs signal activation in microglia. Targeting type I IFNs signal is proven to be an effective strategy for neuropathic pain treatment after SCI.

Traumatic brain injury enhances the intrinsic excitation and excitatory transmission of granule cells
Traumatic brain injury (TBI) is a leading cause of morbidity and mortality worldwide, affecting millions of people each year. TBI can lead to a wide range of physical and cognitive impairments. It is also known to impact on neuronal excitability and synaptic functions. Although hippocampal impairments have been widely described following TBI, the specific effects on dentate gyrus (DG), which act as gatekeeper of hippocampal information processing and as a filter of excessive or aberrant input activity, remains to be fully elucidated. In this study we investigated the effects of controlled cortical impact (CCI), as a model of TBI, on the excitability of granule cells and excitatory postsynaptic transmission in the DG at three different time periods, 3 days, 15 day and 4 months after the injury. Our results indicate TBI does not provoke changes in passive membrane properties of granule cells. By applying dimensionality reduction analysis of action potential properties, we were able to identify the variables that exhibited significant short- medium and long-term changes. Indeed, we observed that half-width, amplitude and overshoot of action potential were greater in TBI cells at different time points. Conversely, duration of afterhyperpolarization was reduced compared to control cells. Lastly, although amplitude of sEPSC did not show differences among groups at any time point, significant changes in frequency of sEPCS were observed in TBI cells at different time points, which did not follow the same temporal evolution as control animals. These findings indicate that at the long term TBI increases the intrinsic excitation of granule cells and excitatory synaptic activity of the DG.

DEFICIENCY OF THE NUTRIENT SENSOR CPT1c IN SF1 NEURONS DISRUPTS THE ENDOCANNABINOID SYSTEM RESULTING IN COMPROMISED SATIETY AND FUEL SELECTION UPON FAT INTAKE
The SF1 neurons of the ventromedial hypothalamus (VMH) are pivotal in governing body weight and adiposity, particularly in response to a high-fat diet (HFD). Previous studies have shown that the activation of SF1 neurons induces satiety, increases energy expenditure, and promotes the preferential use of fats as energy substrate. Furthermore, SF1 neurons are necessary for recovering from insulin-induced hypoglycemia. Here we demonstrate the essential role of the nutritional sensor CPT1c in the activation of SF1 neurons by dietary fats. Mice deficient in CPT1C in SF1 neurons (SF1-CPT1c-KO) are unable to adjust their caloric intake during the initial exposure to a HFD. This is associated with an impaired metabolic transition in the liver, muscle, and adipose tissue, despite a normal response to a glucose or insulin challenge. During chronic HFD exposure, SF1-CPT1c-KO mice are more prone to obesity and glucose intolerance than controls. CPT1c deficiency in SF1 neurons also leads to alterations in hypothalamic endocannabinoid levels and their metabolism. Our findings posit CPT1C in SF1 neurons as a sensor for dietary fats, regulating satiety responses and nutrient partitioning likely through the modulation of the endocannabinoid system.

Progressive engagement of SST+ interneurons via Elfn1 regulates the barrel-septa response identity in the somatosensory cortex of mice
The vibrissae system of rodents, akin to human hands and fingers, provides somatosensory information coming from individual whiskers for object exploration and recognition. Just as separated digits enhance somatosensation in humans, the ability of mice to sense objects through multiple whiskers in segregated streams is crucial. The segregation begins at the level of the whiskers and is maintained through their precise somatotopic organization in the Brainstem[->] Thalamus[->] Cortex axis, culminating in the so-called barrels and the in-between "spaces" called septa. Here, by performing in-vivo silicon probe recordings simultaneously in the barrel and septa domains in mice upon repeated 10Hz single and multi-whisker stimulation, we identify and characterize a temporal divergence in the spiking activity between these domains. Further, through genetic fate-mapping, we reveal that cortical SST+ and VIP+ inhibitory neurons show a layer-dependent differential preference in septa versus barrel domains. Utilizing a genetic manipulation that affects the temporal facilitation dynamics onto only these two inhibitory cell classes, we largely abolish the temporal response divergence between the two cortical domains. Finally, using in-vivo viral tracing, whole-brain clearing and imaging, we show a differential barrel and septa projection pattern to cortical regions S2 and M1. We hence reveal that local temporally engaging cortical inhibition provided by SST+ neurons contribute to the functional segregation of barrel and septa domains and potentially their downstream targets.

TDP-43 loss induces extensive cryptic polyadenylation in ALS/FTD
Nuclear depletion and cytoplasmic aggregation of the RNA binding protein TDP-43 is the hallmark of ALS, occurring in over 97% of cases. A key consequence of TDP-43 nuclear loss is the de-repression of cryptic exons. Whilst TDP-43 regulated cryptic splicing is increasingly well catalogued, cryptic alternative polyadenylation (APA) events, which define the 3' end of last exons, have been largely overlooked, especially when not associated with novel upstream splice junctions. We developed a novel bioinformatic approach to reliably identify distinct APA event types: alternative last exons (ALE), 3'UTR extensions (3'Ext) and intronic polyadenylation (IPA) events. We identified novel neuronal cryptic APA sites induced by TDP-43 loss of function by systematically applying our pipeline to a compendium of publicly available and in house datasets. We find that TDP-43 binding sites and target motifs are enriched at these cryptic events and that TDP-43 can have both repressive and enhancing action on APA. Importantly, all categories of cryptic APA can also be identified in ALS and FTD post mortem brain regions with TDP-43 proteinopathy underlining their potential disease relevance. RNA-seq and Ribo-seq analyses indicate that distinct cryptic APA categories have different downstream effects on transcript and translation. Intriguingly, cryptic 3'Exts occur in multiple transcription factors, such as ELK1, SIX3, and TLX1, and lead to an increase in wild-type protein levels and function. Finally, we show that an increase in RNA stability leading to a higher cytoplasmic localisation underlies these observations. In summary, we demonstrate that TDP-43 nuclear depletion induces a novel category of cryptic RNA processing events and we expand the palette of TDP-43 loss consequences by showing this can also lead to an increase in normal protein translation.

The choroid plexus maintains ventricle volume and adult subventricular zone neuroblast pool, which facilitates post-stroke neurogenesis
The brain's neuroreparative capacity after injuries such as ischemic stroke is contained in the brain's neurogenic niches, primarily the subventricular zone (SVZ), which lies in close contact with the cerebrospinal fluid (CSF) produced by the choroid plexus (ChP). Despite the wide range of their proposed functions, the ChP/CSF remain among the most understudied compartments of the central nervous system (CNS). Here we report a mouse genetic tool (the ROSA26iDTR mouse line) for non-invasive, specific, and temporally controllable ablation of CSF-producing ChP epithelial cells to assess the roles of the ChP and CSF in brain homeostasis and injury. Using this model, we demonstrate that ChP ablation causes rapid and permanent CSF volume loss accompanied by disruption of ependymal cilia bundles. Surprisingly, ChP ablation did not result in overt neurological deficits at one-month post-ablation. However, we observed a pronounced decrease in the pool of SVZ neuroblasts following ChP ablation, which occurs due to their enhanced migration into the olfactory bulb. In the MCAo model of ischemic stroke, neuroblast migration into the lesion site was also reduced in the CSF-depleted mice. Thus, our study establishes an important and novel role of ChP/CSF in regulating the regenerative capacity of the adult brain under normal conditions and after ischemic stroke.

Conditional knockout of Shank3 in the ventral CA1 by quantitative in vivo genome-editing impairs social memory
Individuals with autism spectrum disorder (ASD) have a higher prevalence of social memory impairment. A series of our previous studies revealed that hippocampal ventral CA1 (vCA1) neurons possess social memory engram and that the neurophysiological representation of social memory in the vCA1 neurons is disrupted in ASD-associated Shank3 knockout mice. However, whether the dysfunction of Shank3 in vCA1 causes the social memory impairment observed in ASD remains unclear. In this study, we found that vCA1-specific Shank3 conditional knockout (cKO) by the adeno-associated virus (AAV)- or specialized extracellular vesicle (EV)- mediated in vivo gene editing was sufficient to recapitulate the social memory impairment in male mice. Furthermore, the utilization of EV-mediated Shank3-cKO allowed us to quantitatively examine the role of Shank3 in social memory. Our results suggested that there is a certain threshold for the proportion of Shank3-cKO neurons required for social memory disruption. Thus, our study provides insight into the population coding of social memory in vCA1, as well as the pathological mechanisms underlying social memory impairment in ASD.

Encoding of task regularities links grid-like signals to human timing behavior
Grid cells have been proposed to encode task regularities that allow predicting future states. Entorhinal grid-like signals might therefore mirror behavioral biases associated with relying on task regularities, like regression-to-the-mean biases in time estimation. Here, we tested this proposal using functional magnetic resonance imaging and a rapid timing task in humans. Indeed, trial-wise entorhinal activity reflected task accuracy and the degree to which interval estimates regressed towards the mean of all tested intervals. Grid-like signals were observed exclusively for the interval closest to the mean, which was explained by differences in temporal stability across intervals. Finally, both behavioral and entorhinal results were explained by a Bayesian observer model that assumes the integration of current-trial sensory evidence with prior expectations. Together, we find that entorhinal activity and grid-like signals reflect behavioral performance in a timing task, supporting the proposed role of grid cells in encoding task structure for predictive coordination of behavior.

Transcranial Photobiomodulation on the Left Prefrontal Cortex Enhances Mandarin Chinese L1 and L2 Complex Sentence Processing Performances
This study investigated the causal effect of transcranial photobiomodulation (tPBM) over the left prefrontal cortex (LPFC) on syntactically complex Mandarin Chinese first language (L1) and second language (L2) sentence processing performances. Two (L1 and L2) groups of participants (thirty per group) were recruited to receive the double-blind, sham-controlled tPBM intervention, followed by the sentence processing, the verbal working memory (WM), and the visual WM tasks. Results revealed a consistent pattern for both groups: (a) tPBM enhanced sentence processing performance but not verbal WM and visual WM performance; (b) Participants with lower sentence processing performances under sham tPBM benefited more from active tPBM. Taken together, the current study substantiated that tPBM enhanced L1 and L2 sentence processing ability directly without verbal WM interference, and would serve as a promising and cost-effective noninvasive brain stimulation (NIBS) tool for future applications on upregulating the human language faculty.

Temporal Dynamics of Brain Mediation in Predictive Cue-induced Pain Modulation
Pain is not a mere reflection of noxious input. Rather, it is constructed through the dynamic integration of prior predictions with incoming sensory input. However, the temporal dynamics of the behavioral and neural processes underpinning this integration remain elusive. Here, we identified a series of brain mediators that integrated cue-induced expectations with noxious inputs into ongoing pain predictions using a semicircular scale designed to capture rating trajectories. Temporal mediation analysis revealed that during the early-to-mid stages of integration, the frontoparietal and dorsal attention network regions, such as the lateral prefrontal, premotor, and parietal cortex, mediated the cue effects. Conversely, during the mid-to-late stages of integration, the somatomotor network regions mediated the effects of stimulus intensity, suggesting that the integration occurs along the cortical hierarchy from transmodal to unimodal brain systems. Our findings advance the understanding of how the brain integrates prior and sensory information into pain experience over time.

Posture-dependent modulation of marmoset cortical motor maps detected via rapid multichannel epidural stimulation
In this study, rapid topographical changes were detected in the forelimb motor maps in the primary motor cortex (M1) of awake marmoset monkeys using our previously developed accurate short-time stimulation mapping procedure (Takemi et al. 2017; Kosugi et al. 2018). The results revealed that although the hotspot (the location in M1 that elicited a forelimb muscle twitch with the lowest stimulus intensity) remained constant across postures, the stimulus intensity required to elicit the forelimb muscle twitch in the perihotspot region and the size of motor representations were posture-dependent. Hindlimb posture was particularly effective in inducing these modulations. The angle of the body axis relative to the gravitational vertical line did not alter the motor maps. These results provide a proof of concept that a rapid stimulation mapping system with chronically implanted cortical electrodes can capture the dynamic regulation of forelimb motor maps in natural conditions. The flexible nature of the motor maps necessitates the reconsideration of the results of motor control and neuroplasticity studies. Neural mechanisms regulating forelimb muscle representations in M1 by the hindlimb sensorimotor state warrant further exploration.

Single-cell RNA sequencing of iPSC-derived brain organoids reveals Treponema pallidum infection inhibiting neurodevelopment
Congenital syphilis is a vertically transmitted bacterial infection caused by Treponema pallidum, often causing multidomain neurodevelopmental disabilities. However, little is known about the pathogenesis of this disease. Brain organoids platform derived from the induced pluripotent stem cell (iPSC) is employed and exposed to T. pallidum infection for modelling congenital neurodevelopmental impairment. Single-cell RNA sequencing is used for identifying the subpopulations of differentially expressed genes and cellular heterogeneity and reconstructing differentiation trajectories following T. pallidum infection. The results reveal that T. pallidum infection influences the formation of neural rosette structures, reduces the cell number of the neural progenitor cell subcluster 1B (subNPC1B) and hindbrain neurons, and affects the neurodevelopment of the brain organoid. Moreover, it is speculated that T. pallidum inhibit the hindbrain neuron cell number through the suppression of subNPC1B subgroup in the organoids and inhibits transcription factor 3 activity in the subNPC1B-hindbrain neuronal axis. This is the first report on the inhibited effects of T. pallidum on the neurodevelopment of the iPSC-derived brain organoid model. It is concluded that T. pallidum could inhibit the differentiation of subNPC1B in brain organoids, thereby reducing the differentiation from subNPC1B to hindbrain neurons, and ultimately affecting the development and maturation of hindbrain neurons.

Satb2 regulates pyramidal cell differentiation and the development of feedforward inhibitory circuits in CA1 hippocampus
In CA1 hippocampus, pyramidal cells (PCs) can be separated into two classes, deep or superficial, based on their radial position. In mice, superficial PCs receive fewer inhibitory synapses from parvalbumin (PV)-expressing interneurons than deep PCs, resulting in weaker feedforward inhibition of input from CA3 Schaffer collaterals. The molecular mechanisms that control PC differentiation and integration into hippocampal circuits remain unknown. Using mice, we found that the transcriptional regulator SATB2 is expressed in superficial PCs but absent from deep PCs at birth. Next, we conditionally knocked out (cKO) Satb2 from PCs during early development and then investigated inhibitory circuits using whole-cell recordings in acute slices from juveniles. In Satb2 cKO mice, feedforward inhibition of superficial PCs increased to match that observed in deep PCs. In paired recordings between PCs and PV+ interneurons, we found increased strength of inhibitory synapses selectively to superficial PCs. This was due to increased density of perisomatic PV+ synaptic puncta. Thus, Satb2 expression in superficial PCs suppresses PV+ interneuron synapse formation to establish differential feedforward inhibition in CA1 hippocampus.