bioRxiv Subject Collection: Neuroscience's Journal

Multiregional Representations of Intertemporal Decision Making in Human Single Neurons
Characterization of the neural basis of delay discounting provides insight into the origin of impulsive decision-making, which underlies several psychiatric diseases including substance use disorder. Here, we identify human single unit representations of decisions, and their level of difficulty, in the orbitofrontal cortex, hippocampus and amygdala that are related to preferences for immediate vs. delayed rewards. Results provide an initial account of multiregional intracranial computations related to impulsive behaviors in humans.

Slow Oscillations Modulate Functional Brain Changes Supporting Working Memory
Working memory (WM), the temporary mental storage and manipulation of information, is a skill that can improve with training. Sleep, and specifically slow oscillations (SOs), has been linked with WM improvement, yet it is unknown how processing during SOs modulates WM function across sleep. The current study examines how WM-related neural processing changes with sleep, and how these changes are related to activity during SOs. To do so, participants performed a WM task during fMRI before and after sleep, and the first 2.5 hrs of sleep was monitored by simultaneous EEG-fMRI. Reliable overnight changes in WM-related activity patterns were found, with reduced recruitment of the dorsal precuneus after compared to before sleep. Moreover, greater neural activation during SOs was associated with reduced overnight recruitment during WM across multiple levels of analysis. Our findings highlight the important role of SOs, elucidating how SOs may support changes in WM function across sleep.

Early and widespread engagement of the cerebellum during hippocampal epileptiform activity
Despite research illustrating the cerebellum may be a critical circuit element in the epilepsies, remarkably little is known about cerebellar engagement during seizures. We therefore implemented a novel method for repeated imaging of the cerebellum in awake, chronically epileptic animals. We found widespread changes in cerebellar calcium signals during behavioral seizures and during hippocampal seizures that remained electrographic only, arguing against cerebellar modulation simply reflecting motor components. Moreover, even brief interictal spikes produced widespread alterations in cerebellar activity. Changes were noted in the anterior and posterior cerebellum, along the midline, and both ipsilaterally and contralaterally to the seizure focus. Remarkably, changes in the cerebellum also occurred prior to any noticeable change in the hippocampal electrographic recordings, suggesting a special relationship between the cerebellum and hippocampal epileptiform activity. Together these results underscore the importance of the cerebellum in epilepsy, warranting a more consistent consideration of the cerebellum when evaluating epilepsy patients.

Cone bipolar cell synapses generate transient versus sustained signals in parallel ON pathways of the mouse retina
Parallel processing is a fundamental organizing principle in the nervous system, and understanding how parallel neural circuits generate distinct outputs from common inputs is a key goal of neuroscience. In the mammalian retina, divergence of cone signals into multiple feed-forward bipolar cell pathways forms the initial basis for parallel retinal circuits dedicated to specific visual functions. Here, we used patch-clamp electrophysiology, electron microscopy and two photon imaging of a fluorescent glutamate sensor to examine how kinetically distinct responses arise in transient versus sustained ON alpha RGCs (ON-T and ON-S RGCs) of the mouse retina. We directly compared the visual response properties of these RGCs with their presynaptic bipolar cell partners, which we identified using 3D electron microscopy reconstruction. Different ON bipolar cell subtypes (type 5i, type 6 and type 7) had indistinguishable light-driven responses whereas extracellular glutamate signals around RGC dendrites and postsynaptic excitatory currents measured in ON-T and ON-S RGCs in response to the identical stimuli used to probe bipolar cells were kinetically distinct. Anatomical examination of the bipolar cell axon terminals presynaptic to ON-T and ON-S RGCs suggests bipolar subtype-specific differences in the size of synaptic ribbon-associated vesicle pools may contribute to transient versus sustained kinetics. Our findings indicate bipolar cell synapses are a primary point of divergence in kinetically distinct visual pathways.

BlueRecording: A Pipeline for the efficient calculation of extracellular recordings in large-scale neural circuit models
As the size and complexity of network simulations accessible to computational neuroscience grows, new avenues open for research into extracellularly recorded electric signals. Biophysically detailed simulations permit the identification of the biological origins of the different components of recorded signals, the evaluation of signal sensitivity to different anatomical, physiological, and geometric factors, and selection of recording parameters to maximize the signal information content. Simultaneously, virtual extracellular signals produced by these networks may become important metrics for neuro-simulation validation. To enable efficient calculation of extracellular signals from large neural network simulations, we have developed BlueRecording, a pipeline consisting of standalone Python code, along with extensions to the Neurodamus simulation control application, the CoreNEURON computation engine, and the SONATA data format, to permit online calculation of such signals. In particular, we implement a general form of the reciprocity theorem, which is capable of handling non-dipolar current sources, such as may be found in long axons and recordings close to the current source, as well as complex tissue anatomy, dielectric heterogeneity, and electrode geometries. To our knowledge, this is the first application of this generalized (i.e., non-dipolar) reciprocity-based approach to simulate EEG recordings. We use these tools to calculate extracellular signals from an in silico model of the rat somatosensory cortex and to study signal contribution differences.

Drosophila males require the longitudinal stretch receptors to tremulate their abdomen and produce substrate-borne signals during courtship
Substrate-borne cues are important species-specific signals that are widely used during courtship of many animals, from arthropods to vertebrates. They allow mating partners to communicate with, recognise and choose one another. Animals often produce substrate-borne signals by vibrating a body part, such as the abdomen. During Drosophila courtship, species-specific substrate-borne vibrations are generated by the males regular up-and-down abdominal tremulations and these must be precisely controlled to produce an effective and specific signal. The vibrations immobilise the female, therefore facilitating copulation. It is not known how the males nervous system regulates this abdominal tremulation. Here, we demonstrate a role for the dorsal abdominal longitudinal stretch receptors (LSR), which include the dorsal bipolar dendritic (dbd) neurons. These neurons are a set of conserved proprioceptors found throughout Insecta. We show that impairing the function of dbd neurons through general inhibition results in males exhibiting high level of arhythmic abdominal movements (referred to as bobbing) and decreased level of tremulation. Strikingly, this causes a failure in the females response during courtship. We show that depleting the mechanosensitive ion channel TRPA1 (but not Piezo) in the dbd neurons leads to a similar increase in bobbing movements. Thus, we identify neurons and a key molecular player necessary for males to perform this important mode of communication.

Joint population coding and temporal coherence link an attended talker's voice and location features in naturalistic multi-talker scenes.
Listeners readily extract multi-dimensional auditory objects such as a {acute}localized talker{acute} from complex acoustic scenes with multiple talkers. Yet, the neural mechanisms underlying simultaneous encoding and linking of different sound features -- for example, a talker{acute}s voice and location -- are poorly understood. We analyzed invasive intracranial recordings in neurosurgical patients attending to a localized talker in real-life cocktail party scenarios. We found that sensitivity to an individual talker{acute}s voice and location features was distributed throughout auditory cortex and that neural sites exhibited a gradient from sensitivity to a single feature to joint sensitivity to both features. On a population level, cortical response patterns of both dual-feature sensitive sites but also single-feature sensitive sites revealed simultaneous encoding of an attended talker{acute}s voice and location features. However, for single-feature sensitive sites, the representation of the primary feature was more precise. Further, sites which selective tracked an attended speech stream concurrently encoded an attended talker{acute}s voice and location features, indicating that such sites combine selective tracking of an attended auditory object with encoding of the object{acute}s features. Finally, we found that attending a localized talker selectively enhanced temporal coherence between single-feature voice sensitive sites and single-feature location sensitive sites, providing an additional mechanism for linking voice and location features in multi-talker scenes. These results demonstrate that a talker{acute}s voice and location features are linked during multi-dimensional object formation in naturalistic multi-talker scenes by joint population coding as well as by temporal coherence between neural sites.

Differential effects of prolonged post-fixation on immunohistochemical and histochemical staining for postmortem human brains
Immunohistochemical (IHC) and histochemical (HC) staining is widely used for human brains postfixed in formalin for years and decades. Understanding the effect of prolonged post-fixation, postmortem interval (PMI) and age on these staining procedures is important for interpreting their outcomes, thus improving diagnosis and research of brain disorders. In this study, we performed both IHC and HC staining for prefrontal cortex (PFC) of postmortem human brains postfixed for 1, 5, 10, 15 and 20 years. A negative correlation was detected between the intensity of neuron marker NeuN, microglia marker Iba1, cresyl violet and Luxol fast blue staining versus post-fixation times. By contrast, a positive correlation was seen between the intensity of astrocyte marker GFAP and H&E staining versus post-fixation times. No correlation was found between most of these parameters versus age or PMI. These data suggest that prolonged post-fixation exerts both positive and negative effects, but age and PMI have limited effects, on these IHC and HC parameters. Hence these differential changes need to be considered in the interpretation of the results when using tissues with prolonged post-fixation. It is recommended to perform IHC and HC staining for human brains with similar post-fixation time to offset its impact on downstream analyses.

STEMorph: Morphed Emotional Face Stimuli
Emotion recognition is crucial for interpreting social cues, with facial expressions being the primary channel for such communication. Despite its importance, emotion recognition is often influenced by biases, in which we show a systematic recognition advantage for a particular emotion. These biases, however, are inconsistently reported across studies, likely due to methodological variations, underlining the necessity for a standardized approach. Traditional face morphing methods, although widely used, can create unnatural-looking stimuli, which may confound the interpretation of emotions. Addressing this issue, we here introduce STEMorph, a validated stimulus set based on the NimStim facial expression set. Our approach utilizes neutral-anchored morphing and neural-network-generated masks to ensure the natural appearance and integrity of the depicted emotions. We validated our stimulus set by presenting morphed emotional faces to participants and asking them to rate the emotional valence of each stimulus. The STEMorph's validity was confirmed through linear regression analysis, showing a strong correlation between subjective ratings and targeted emotional states. Additionally, subgroup analysis by gender of both the depicted faces and the participants showed uniform results. Moreover, we confirmed the reliability of STEMorph by asking the same participants to rate the stimuli two weeks later. In conclusion, by introducing a controlled, validated, and ecologically valid stimulus set of emotional faces, our study paves the way for further investigations aimed at unraveling the complexities of facial emotion recognition and deepening our understanding of this vital aspect of human interaction.

Shared spatial selectivity in early visual cortex and face-selective brain regions
Face recognition is widely considered to be ''special'', involving dedicated brain regions with unique patterns of selectivity. This contrasts with increasing evidence for common patterns of 'visuospatial coding', where even high-level category-selective areas share the spatial properties of earlier brain regions. Here we examined whether the retinotopic properties of face-selective areas vary around the visual field in a similar fashion to those of early visual cortex, and whether these spatial properties could explain variations in face perception around the visual field. We carried out retinotopic mapping of early (V1-V3) and face-selective cortical regions (OFA, pFus, mFus) using large-field bars of faces (21{degrees} eccentricity), with spatial selectivity measured via population receptive field (pRF) analysis. While pRFs were considerably larger in face-selective regions than in V1-V3, their size did not vary consistently either across areas or in line with behavioural anisotropies. However, both early cortex and face-selective areas show a greater number of pRFs and a concomitant increase in visual field coverage along the horizontal vs. vertical meridian and in the lower vs. upper field. Variations in our face-recognition abilities around the visual field could thus be driven by these differences in sampling. We also show that pRF numbers (and subsequent coverage) in mFus were typically greater for upright than inverted faces, suggesting these properties could similarly support the perceptual advantage for upright faces, at least in part. The commonality of these variations in visual field sampling between face-selective cortex and earlier visual regions further support a hierarchical model whereby the spatial selectivity of higher-level areas is built upon the selectivity of lower regions, even for specialised face processing.

The hippocampus supports interpolation into new states during category abstraction
The hippocampus forms concepts by integrating multi-feature relations into a unified representation. A common yet unconfirmed assumption is that such cognitive maps afford interpolations to never-experienced states. We approach this question as a category-learning problem in which prototypes are omitted from training but guide category-based decisions in a subsequent feature-inference task. Consistent with behavior, missing inferred stimulus features were represented at prototypical values in neocortex. This cortical completion effect correlated with hippocampal responses, which in turn reflected the distance between imagined prototypes and experienced exemplars. This was paralleled by a learning-dependent grid-like representation of the underlying concept space in entorhinal cortex. Our results suggest that abstracted prototypes correspond to interpolated central states in a cognitive map that guide cortical pattern completion during category-based decisions.

An integrated microfluidic and fluorescence platform for probing in vivo neuropharmacology
Neurotechnologies and genetic tools for dissecting neural circuit functions have advanced rapidly over the past decade, although the development of complementary pharmacological methodologies has comparatively lagged. Understanding the precise pharmacological mechanisms of neuroactive compounds is critical for advancing basic neurobiology and neuropharmacology, as well as for developing more effective treatments for neurological and neuropsychiatric disorders. However, integrating modern tools for assessing neural activity in large-scale neural networks with spatially localized drug delivery remains a major challenge. Here, we present a dual microfluidic-photometry platform that enables simultaneous intracranial drug delivery with neural dynamics monitoring in the rodent brain. The integrated platform combines a wireless, battery-free, miniaturized fluidic microsystem with optical probes, allowing for spatially and temporally specific drug delivery while recording activity-dependent fluorescence using genetically encoded calcium indicators (GECIs), neurotransmitter sensors GRABNE and GRABDA, and neuropeptide sensors. We demonstrate the performance this platform for investigating neuropharmacological mechanisms in vivo and characterize its efficacy in probing precise mechanistic actions of neuroactive compounds across several rapidly evolving neuroscience domains.

Distinct functional classes of CA1 hippocampal interneurons are modulated by cerebellar stimulation in a coordinated manner
There is mounting evidence that the cerebellum impacts hippocampal functioning, but the impact of the cerebellum on hippocampal interneurons remains obscure. Using miniscopes in freely behaving animals, we find optogenetic stimulation of Purkinje cells alters the calcium activity of a large percentage of CA1 interneurons. This includes both increases and decreases in activity. Remarkably, this bidirectional impact occurs in a coordinated fashion, in line with interneurons' functional properties. Specifically, CA1 interneurons activated by cerebellar stimulation are commonly locomotion-active, while those inhibited by cerebellar stimulation are commonly rest-active interneurons. We additionally find that subsets of CA1 interneurons show altered activity during object investigations, suggesting a role in the processing of objects in space. Importantly, these neurons also show coordinated modulation by cerebellar stimulation: CA1 interneurons that are activated by cerebellar stimulation are more likely to be activated, rather than inhibited, during object investigations, while interneurons that show decreased activity during cerebellar stimulation show the opposite profile. Therefore, CA1 interneurons play a role in object processing and in cerebellar impacts on the hippocampus, providing insight into previously noted altered CA1 processing of objects in space with cerebellar stimulation. We examined two different stimulation locations (IV/V Vermis; Simplex) and two different stimulation approaches (7Hz or a single 1s light pulse) - in all cases, the cerebellum induces similar coordinated CA1 interneuron changes congruent with an explorative state. Overall, our data show that the cerebellum impacts CA1 interneurons in a bidirectional and coordinated fashion, positioning them to play an important role in cerebello-hippocampal communication.

Ketamine reverses stress-induced hypersensitivity to sunk costs
How mood interacts with information processing in the brain is thought to mediate the maladaptive behaviors observed in depressed individuals. However, the neural mechanisms underlying impairments in emotion-cognition interactions are poorly understood. This includes influencing the balance between how past-sensitive vs. future-looking one is during decision-making. Recent insights from the field of neuroeconomics offer novel approaches to study changes in such valuation processes in a manner that is biologically tractable and readily translatable across species. We recently discovered that rodents are sensitive to sunk costs - a feature of higher cognition previously thought to be unique to humans. The sunk costs bias describes the phenomenon in which an individual overvalues and escalates commitment to continuing an ongoing endeavor, even if suboptimal, as a function of irrecoverable past (sunk) losses - information that, according to classic economic theory, should be ignored. In the present study, mice were exposed to chronic social defeat stress paradigm, a well-established animal model used for the study of depression. Mice were then tested on our longitudinal neuroeconomic foraging task, Restaurant Row. We found mice exposed to this severe stressor displayed an increased sensitivity to sunk costs, without altering overall willingness to wait. Mice were then randomly assigned to receive a single intraperitoneal injection of either saline or ketamine (20 mg/kg). We discovered that stress-induced hypersensitivity to sunk costs was renormalized following a single dose of ketamine. Interestingly, in non-defeated mice, ketamine treatment completely abolished sunk cost sensitivity, causing mice to no longer value irrecoverable losses during re-evaluation decisions who instead based choices solely on the future investment required to obtain a goal. These findings suggest that the antidepressant effects of ketamine may be mediated in part through changes in the processing of past-sensitive information during on-going decision-making, reducing its weight as a potential source of cognitive dissonance that could modulate behavior and instead promoting more future-thinking behavior.

Sex dependent effects of amyloidosis on functional network hub topology is associated with downregulated neuronal gene signatures in the APPswe/PSEN1dE9 double transgenic mouse
Extracellular beta-amyloid (A{beta}) is thought to cause impairments in brain wide functional connectivity, although mechanisms linking A{beta} to broader functional network processing remain elusive. In the present study, we evaluated the effects of A{beta} on fear memory and functional connectome measures in male and female mice. Middle-aged (9-11mo) double transgenic APP-PS1 mice and age and sex-matched controls were tested on a fear conditioning protocol and then imaged at 11.1 Tesla. Brains were harvested and processed for analysis of A{beta} plaques and Iba1 immunolabeling in neocortical areas, hippocampus, and basolateral amygdala. Additional RNA sequencing data from separate age, strain, and sex matched mice were analyzed for differentially expressed genes (DEGs) and weighted gene co-expression networks. In both male and female mice, we observed increased functional connectivity in a dorsal striatal/amygdala network as a result of A{beta}. Increased functional connectivity within this network was matched by increases in APP gene expression, A{beta} and Iba1 immunolabeling, and an upregulated cluster of DEGs involved in the immune response. Conversely, the network measure representing node hubness, eigenvector centrality, was increased in prefrontal cortical brain regions, but only in female APP-PS1 mice. This female specific-effect of amyloid was associated with downregulation of a cluster of DEGs involved in cortical and striatal GABA transmission, anxiogenic responses, and motor activity, in female APP-PS1 mice, but not males. Our results contribute to a growing literature linking between A{beta}, immune activation and functional network connectivity. Furthermore, our results reveal effects of A{beta} on gene expression patterns in female mice that may contribute to amyloidosis-induced dysregulation of non-cognitive circuitry.

Competition and integration of visual and goal vector signals for spatial navigation
Integrating different sources of information is essential to successful spatial navigation. For instance, animals must often rely on a combination of visual impressions, self-motion, olfaction, and other signals to navigate to a goal. This is especially important when navigating in uncertain environments, where switching from one source of information to another or integrating multiple sources of information may be required to make navigation decisions. We propose a computational model of the interaction of visual and goal-vector signals based on reinforcement learning and use it to study behavior and spatial representations. Our model demonstrates that the ability to navigate using each information source independently, in addition to integrating them, is crucial to successfully navigating in uncertain environments. Counterintuitively, our model also shows that when one of the signals is removed, navigation may be improved if the remaining signal is reliable and sufficient to navigate, however, this improvement comes at the expense of robustness.

Replay without sharp wave ripples in a spatial memory task.
Sharp-wave ripples in the hippocampus are believed to be a fundamental mechanism for the consolidation of episodic memories. During ripples, hippocampal neurons are re-activated in sequences called replay, which have been hypothesized to reflect episodic memory content. Ripples and replay are usually reported to co-occur, and are commonly thought to reflect the same process. Here we report that, in rats performing an open field spatial memory task, replays readily occur in the complete absence of ripples. Moreover, the occurrence of ripple-less and ripple-containing replays is not random, but precisely organized in terms of virtual space: Ripples are confined to "ripple fields", which are spatially-restricted areas defined over the virtual locations depicted during replay and independent of the actual location of the animal. Similar to allocentric coding by place fields, ripple fields are independent of the direction of travel, and stable throughout the recording session. Ripple fields track changes to environmental structure caused by the addition or subtraction of barriers to movement, consistent with ripples conveying information about the incorporation of novel experiences. Moreover, ripple fields were matched across different rats experiencing the same barrier configuration, highlighting the robustness of the ripple field spatial code. We hypothesize a new relationship between ripples and replay, in which a subset of replays that is particularly relevant to learning or novelty is paired with ripples, in order to promote its selective broadcast to the rest of the brain for consolidation.

Melanopsin ganglion cells in the mouse retina independently evoke pupillary light reflex
Purpose: The pupillary light reflex (PLR) is crucial for protecting the retina from bright light. The intrinsic photosensitive ganglion cells (ipRGCs) in the retina mediate the PLR, which directly sense light and receive inputs from rod/cone photoreceptors. Previous work used genetic knockout mice to reveal that rod/cone photoreceptors drive transient constriction, and ipRGCs drive the sustained component. We acutely ablated photoreceptors by a chemical injection to examine the role of rod and cone photoreceptors in PLR. Methods: PLR and the multiple electrode array (MEA) recording were conducted with C57BL6/J (wildtype: WT) and Cnga3-/-; Gnat1-/- (rod/cone dysfunctional) mice. n-Nitroso-n-methylurea (MNU) was applied to C57 mice by intraperitoneal injection, and PLR was conducted after 5-7 days of injection. Three different light levels (mesopic, low photopic, and high photopic) were tested. Immunohistochemistry was conducted using the anti-Gnat1 and anti-melanopsin antibodies with DAPI. Results: PLR was induced by all light levels we tested, and the level of constriction increased as the light level increased. After the MNU injection, PLR was not induced at mesopic light stimulus, but was fully induced by high light. The level of PLR was identical between WT and MNU mice, suggesting that ipRGCs fully contributed to the PLR at this light level. Immunohistochemistry revealed that photoreceptors were ablated by the MNU injection, but ipRGCs were preserved. The MEA recording revealed that a population of ipRGCs generated fast and robust spikes in MNU-injected retinal tissues in ex vivo. Conclusions: Contrary to previous observations, our results demonstrate that ipRGCs are the major contributor to the PLR induced by high light.

Task-irrelevant stimuli reliably boost phasic pupil-linked arousal but do not affect decision formation
The arousal systems of the brainstem, specifically the locus coeruleus-noradrenaline system, respond "phasically" during decisions. These central arousal transients are accompanied by dilations of the pupil. Mechanistic attempts to understand the impact of phasic arousal on cognition would benefit from the ability to experimentally manipulate arousal in a temporally precise manner. Here, we evaluated a non-invasive candidate approach for such a manipulation in humans: presenting task-irrelevant auditory stimuli at different latencies during the execution of a challenging task. Task-irrelevant auditory stimuli drive responses of brainstem nuclei involved in the control of pupil size. But it is unknown whether such sound-evoked responses mimic the central arousal transients evoked during cognitive computations. A large body of evidence has implicated central arousal transients in a bias reduction during challenging perceptual decisions. We thus used challenging visual decisions as a testbed, combining them with task-irrelevant sounds of varying onset latency or duration. Across three experiments, the sounds consistently elicited well-controlled pupil responses that superimposed onto task-evoked responses. While we replicated a negative correlation between task-evoked pupil responses and bias established in previous work, the task-irrelevant sounds had no behavioral effect. This dissociation suggests that cognitive task engagement and task-irrelevant sounds may recruit distinct neural systems contributing to the control of pupil size.

Cortical Dynamics during Contour Integration
Integrating visual elements into contours is important for object recognition. Previous studies emphasized the role that the primary visual cortex (V1) plays in this process. However, recent evidence suggests that contour integration relies on the coordination of hierarchical substrates of cortical regions through recurrent connections. Many previous studies presented the contour at the same onset-time as the trial, which caused the subsequent neural imaging data to incorporate both visual evocation and contour integration activities, and thus confounding the two. In this study, we varied both the contour onset-time and contour fidelity and used EEG to examine the cortical activities under these conditions. Our results suggest that the middle temporal N300 represents the grouping and integration of visual elements into contours. Before this signature, we observed interhemispheric connections between lateral frontal and posterior parietal regions that were contingent on the contour location and peaked at around 150ms after contour appearance. Also, the magnitudes of connections between medial frontal and superior parietal regions were dependent on the timing of contour onset and peaked at around 250ms after contour onset. These activities appear to be related to the bottom-up and top-down attentional processing during contour integration, respectively, and shed light on how these processes cooperate dynamically during contour integration.

A toolbox for genetic targeting of the claustrum
The claustrum (CLA), a subcortical nucleus in mammals, essentially composed of excitatory projection neurons and known for its extensive connections with the neocortex, has recently been associated with a variety of functions ranging from consciousness to impulse control. However, research on the CLA has been challenging due to difficulties in specifically and comprehensively targeting its neuronal populations. In various cases, this limitation has led to inconsistent findings and a lack of reliable data. In the present work, we describe the expression profile of the Smim32 gene, which is almost exclusively transcribed in excitatory neurons of the CLA and the endopiriform nucleus, as well as in inhibitory neurons of the thalamic reticular nucleus. Leveraging this unique expression pattern, we developed a series of Cre- and Flippase-expressing knockin and BAC transgenic mouse lines with different expression profiles. With these novel tools in hand, we propose new standards for the interrogation of CLA function.

SAUSI: a novel assay for measuring social anxiety and motivation
Social anxiety is one of the most prevalent mental health disorders, though the underlying neurobiology is poorly understood. Progress in understanding the etiology of social anxiety has been hindered by the lack of comprehensive tools to assess social anxiety in model systems. Here, we created a new behavioral task - Selective Access to Unrestricted Social Interaction (SAUSI), which combines elements of social motivation, hesitancy, decision-making, and free interaction to enable the wholistic assessment of social anxiety-like behaviors in mice. Using this novel assay, we found that social isolation-induced social anxiety-like behaviors in female mice are largely driven by increases in social fear, social hesitancy, and altered ultrasonic vocalizations. Deep learning analyses were able to computationally identify a unique behavioral footprint underlying the state produced by social isolation, demonstrating the compatibility of modern computational approaches with SAUSI. Finally, we compared the results of SAUSI to traditionally social assays including the 3-chamber sociability assay and the resident intruder task. This revealed that behavioral changes induced by isolation were highly context dependent, and that while fragments of social anxiety measured in SAUSI were replicable across other tasks, a wholistic assessment was not obtainable from these alternative assays. Our findings debut a novel task for the behavioral toolbox - one which overcomes limitations of previous assays, allowing for both social choice as well as free interaction, and offers a new approach for assessing social anxiety in rodents.

Neural Processing of Naturalistic Audiovisual Events in Space and Time
Our brain seamlessly integrates distinct sensory information to form a coherent percept. However, when real-world audiovisual events are perceived, the specific brain regions and timings for processing different levels of information remain less investigated. To address that, we curated naturalistic videos and recorded fMRI and EEG data when participants viewed videos with accompanying sounds. Our findings reveal early asymmetrical cross-modal interaction, with acoustic information represented in both early visual and auditory regions, while visual information only identified in visual cortices. The visual and auditory features were processed with similar onset but different temporal dynamics. High-level categorical and semantic information emerged in multi-modal association areas later in time, indicating late cross-modal integration and its distinct role in converging conceptual information. Comparing neural representations to a two-branch deep neural network model highlighted the necessity of early fusion to build a biologically plausible model of audiovisual perception. With EEG-fMRI fusion, we provided a spatiotemporally resolved account of neural activity during the processing of naturalistic audiovisual stimuli.

Immunotherapy-related cognitive impairment after CAR T cell therapy in mice
Persistent central nervous system (CNS) immune dysregulation and consequent dysfunction of multiple neural cell types is central to the neurobiological underpinnings of a cognitive impairment syndrome that can occur following traditional cancer therapies or certain infections. Immunotherapies have revolutionized cancer care for many tumor types, but the potential long-term cognitive sequelae are incompletely understood. Here, we demonstrate in mouse models that chimeric antigen receptor (CAR) T cell therapy for both CNS and non-CNS cancers can impair cognitive function and induce a persistent CNS immune response characterized by white matter microglial reactivity and elevated cerebrospinal fluid (CSF) cytokines and chemokines. Consequently, oligodendroglial homeostasis and hippocampal neurogenesis are disrupted. Microglial depletion rescues oligodendroglial deficits and cognitive performance in a behavioral test of attention and short-term memory function. Taken together, these findings illustrate similar mechanisms underlying immunotherapy-related cognitive impairment (IRCI) and cognitive impairment following traditional cancer therapies and other immune challenges.

Automated segmentation of epilepsy surgical resection cavities: comparison of four methods to manual segmentation
Accurate resection cavity segmentation on MRI is important for neuroimaging research involving epilepsy surgical outcomes. Manual segmentation, the gold standard, is highly labour intensive. Automated pipelines are an efficient potential solution; however, most have been developed for use following temporal epilepsy surgery. Our aim was to compare the accuracy of four automated segmentation pipelines following surgical resection in a mixed cohort of subjects following temporal or extra temporal epilepsy surgery. We identified 4 open-source automated segmentation pipelines. Epic-CHOP and ResectVol utilise SPM-12 within MATLAB, while Resseg and Deep Resection utilise 3D U-net convolutional neural networks. We manually segmented the resection cavity of 50 consecutive subjects who underwent epilepsy surgery (30 temporal, 20 extratemporal). We calculated Dice similarity coefficient (DSC) for each algorithm compared to the manual segmentation. No algorithm identified all resection cavities. ResectVol (n=44, 88%) and Epic-CHOP (n=43, 86%) were able to detect more resection cavities than Resseg (n=22, 44%, P<0.001) and Deep Resection (n=21, 42%, P<0.001). The SPM-based pipelines (Epic-CHOP and ResectVol) performed better than the deep learning-based pipelines in the overall and extratemporal surgery cohorts, however there was no difference between methods in the temporal surgery cohort. These pipelines could be applied to machine learning studies of outcome prediction to improve efficiency in pre-processing data, however human quality control is still required.

An algorithm for identifying task-specific brain subnetworks using the visuomotor system as an example
We describe an algorithm that identifies a subnetwork of brain regions involved in producing a task-specific behavior, here visuomotor behavior, from an anatomically defined primate brain connectome. The algorithm first finds the brain regions connected to an output region (here, primary motor cortex, M1) by one connection. It then identifies all regions, termed layer 2 regions, connected to these layer 1 regions by one connection. This process continues until the layer containing the input region (here, primary visual cortex, V1) is reached. The algorithm then finds, subject to a user-set maximum step number, all paths linking the input and output regions. The brain regions in these paths constitute the initial subnetwork identification that performs the task. Regions known not to be task-involved (for example, regions in the ventral stream of visual information vs. the dorsal stream, which helps generate visuomotor behavior) are then removed. Structural subnetwork analysis showed that the intraparietal sulcus of the parietal cortex (PCIP) was most, and the secondary visual (V2) and superior parietal (PCS) cortices second-most, central to local network activity. Changing PCIP, V2 and PCS activity was thus most likely to alter activity of the entire subnetwork. Model sufficiency was tested by instantiating each brain region inherent activity with multiple versions of a simple two-dimensional (2D) model that can produce oscillatory activity and synaptically interconnecting the regions to produce a macroscopic visuomotor model. The model reproduced the experimental local field potential (LFP) activity of the brain regions identified as part of the visuomotor subnetwork.

Stress hyperglycemia exacerbates inflammatory brain injury after stroke
Post-stroke hyperglycemia occurs in 30% - 60% of ischemic stroke patients as part of the systemic stress response, but neither clinical evidence nor pre-clinical studies indicate whether post-stroke hyperglycemia affects stroke outcome. Here we investigated this issue using a mouse model of permanent ischemia. Mice were maintained either normoglycemic or hyperglycemic during the interval of 17 - 48 hours after ischemia onset. Post-stroke hyperglycemia was found to increase infarct volume, blood-brain barrier disruption, and hemorrhage formation, and to impair motor recovery. Post-stroke hyperglycemia also increased superoxide formation by peri-infarct microglia/macrophages. In contrast, post-stroke hyperglycemia did not increase superoxide formation or exacerbate motor impairment in p47phox-/- mice, which cannot form an active superoxide-producing NADPH oxidase-2 complex. These results suggest that hyperglycemia occurring hours-to-days after ischemia can increase oxidative stress in peri-infarct tissues by fueling NADPH oxidase activity in reactive microglia/macrophages, and by this mechanism contribute to worsened functional outcome.

Roles and mechanisms of leptomeningeal collaterals in human distal MCA territory ischemia
Objective: Leptomeningeal collaterals (LMCs) provided hemodynamic support and reperfusion during acute ischemic stroke (AIS). Although regulation details have been deeply acquired from animal models, human cortex may share limited hemodynamic patterns due to larger physical scale that needs further investigation. Approach and Results: We performed 'sequential hierarchical blocking' during awake craniotomy on fourteen human subjects to mimic AIS in middle cerebral artery (MCA) M4 segment territory. Widefield microscope was applied to reveal microcirculation of LMCs. Relative flow rate (RFR) was measured to evaluate the impact of LMCs hierarchy on microcirculation maintenance. Single-cell sequencing and spatial transcriptomics were further performed to analyze the mechanism of different LMCs recruitment abilities. LMCs RFR decreased to 30.75% immediately (95% CI, 6.64 - 54.86%, P < 0.001), and about 80.25% RFR was finally recovered within 5 minutes (95% CI, 55.2 - 105.3%, P = 0.0034) during M4 occlusion. For M5 and pial branches occlusion, RFR decreased to 55.78% with no further recovery (95% CI, 22.50-89.05%, P = 0.014), and 4 in 11 subjects had no valid microcirculation. For subjects with better recruitment ability, the proportion of arteriole is much higher in leptomeninx (76 - 79% vs. 36 - 56%). There were more significant interaction pairs associated with key signaling pathways between arteriole and neuron/astrocyte (TGF-beta signaling pathway, ECM-receptor interaction). Conclusion: Abundant LMCs supported hemodynamic stability during AIS in human subjects. The proportion of arteriole is much higher in leptomeninx for subjects with better recruitment ability. The Active neuron/astrocyte - arteriole interaction may improve LMCs recruitment.

Temporal prediction captures key differences between spiking excitatory and inhibitory V1 neurons
Neurons in primary visual cortex (V1) respond to natural scenes with a sparse and irregular spike code that is carefully balanced by an interplay between excitatory and inhibitory neurons. These neuron classes differ in their spike statistics, tuning preferences, connectivity statistics and temporal dynamics. To date, no single computational principle has been able to account for these properties. We developed a recurrently connected spiking network of excitatory and inhibitory units trained for efficient temporal prediction of natural movie clips. We found that the model exhibited simple and complex cell-like tuning, V1-like spike statistics, and, notably, also captured key differences between excitatory and inhibitory V1 neurons. This suggests that these properties collectively serve to facilitate efficient prediction of the sensory future.

Amyloid beta glycation leads to neuronal mitochondrial dysfunction and Alzheimers pathogenesis through VDAC1-dependent mtDNA efflux
Amyloid beta (A{beta}), a stable protein, undergoes posttranslational glycation, forming glycated A{beta} (gA{beta}), an advanced glycation end product (AGE) observed in Alzheimers' disease (AD), yet the pathological role of gA{beta} remains understudied. This work explores the role of gA{beta} in inducing neuronal mitochondrial DNA (mtDNA) efflux in a VDAC1-dependent manner and in activating the innate immune cGAS-STING pathway in AD. Findings demonstrate cGAS-mtDNA binding induced by gA{beta} in neuro-cytoplasm along with cGAS-STING activation in aged AD mice and human AD brains. Knockdown of RAGE, cGAS, or STING protects APP mice from mitochondrial dysfunction and AD-like pathology, as does inhibiting VDAC1. Moreover, RAGE inhibition in APP knock-in mice, coupled with spatially enhanced resolution omics-sequencing, confirms downregulation of innate immune responses and disease-associated genes in AD. Therefore, this study identifies a crucial link between gA{beta} and innate immunity, indicating therapeutic targeting of VDAC1, RAGE, or cGAS-STING may enhance resilience against gA{beta}-related pathological insults in AD.

Stress-induced dysfunction of neurovascular astrocytes contributes to sex-specific behavioral deficits
Astrocytes form an integral component of the neurovascular unit, ensheathing brain blood vessels with projections high in aquaporin-4 (AQP4) expression. These AQP4-rich projections facilitate interaction between the vascular endothelium, astrocytes, and neurons, and help stabilize vascular morphology. Studies using preclinical models of psychological stress and post-mortem tissue from patients with major depressive disorder (MDD) have reported reductions in AQP4, loss of astrocytic structures, and vascular impairment in the prefrontal cortex (PFC). Though compelling, the role of AQP4 in mediating stress-induced alterations in blood vessel function and behavior remains unclear. Here, we address this, alongside potential sex differences in chronic unpredictable stress (CUS) effects on astrocyte phenotype, blood-brain barrier integrity, and behavior. CUS led to pronounced shifts in stress-coping behavior and working memory deficits in male -but not female- mice. Following behavioral testing, astrocytes from the frontal cortex were isolated for gene expression analyses. We found that CUS increased various transcripts associated with blood vessel maintenance in astrocytes from males, but either had no effect on- or decreased- these genes in females. Furthermore, CUS caused a reduction in vascular-localized AQP4 and elevated extravasation of a small molecule fluorescent reporter (Dextran) in the PFC in males but not females. Studies showed that knockdown of AQP4 in the PFC in males is sufficient to disrupt astrocyte phenotype and increase behavioral susceptibility to a sub-chronic stressor. Collectively, these findings provide initial evidence that sex-specific alterations in astrocyte phenotype and neurovascular integrity in the PFC contribute to behavioral and cognitive consequences following chronic stress.

Synaptic pruning facilitates online Bayesian model selection
Identifying appropriate structures for generative or world models is essential for both biological organisms and machines. This work shows that synaptic pruning facilitates efficient statistical structure learning. We extend previously established canonical neural networks to derive a synaptic pruning scheme that is formally equivalent to an online Bayesian model selection. The proposed scheme, termed Bayesian synaptic model pruning (BSyMP), utilizes connectivity parameters to switch between the presence (ON) and absence (OFF) of synaptic connections. Mathematical analyses reveal that these parameters converge to zero for uninformative connections, thus providing reliable and efficient model reduction. This enables the identification of a plausible structure for the environmental model, particularly when the environment is characterized by sparse likelihood and transition matrices. Through causal inference and rule learning simulations, we demonstrate that BSyMP achieves model reduction more efficiently than the conventional Bayesian model reduction scheme. These findings indicate that synaptic pruning could be a neuronal substrate underlying structure learning and generalizability in the brain.

Mouse Exploratory behaviour in the open field with and without NAT-1 EEG device: Effects of MK801 and scopolamine
One aspect of reproducibility in preclinical research that is frequently overlooked is the physical condition in which physiological, pharmacological or behavioural recordings are conducted. In this study, the physical conditions of mice were altered through the attachments of wireless electrophysiological recording devices (Neural Activity Tracker-1, NAT-1). NAT-1 devices are miniaturised multichannel devices with on-board memory for direct high-resolution recording of brain activity for >48 hrs. Such devices may limit the mobility of animals and affect their behavioural performance due to the added weight (total weight of approximately 3.4 g). Mice were additionally treated with saline (control), N-methyl-D-aspartate (NMDA) receptor antagonist MK801 (0.85 mg/kg), or the muscarinic acetylcholine receptor blocker scopolamine (0.65 mg/kg) to allow exploration of the effect of NAT-1 attachments in pharmacologically treated mice. We found only minimal differences in behavioural outcomes with NAT-1 attachments in standard parameters of locomotor activity widely reported for the open field test between drug-treatments. Hypoactivity was globally observed as a consistent outcome in MK801-treated subjects and hyperactivity in scopolamine groups regardless of NAT-1 attachments. These data collectively confirm the reproducibility for combined behavioural, pharmacological and physiological endpoints even in the presence of lightweight wireless data loggers. The NAT-1 therefore constitutes a pertinent tool for investigating brain activity in e.g. drug discovery, models of neuropsychiatric and/or neurodegenerative diseases with minimal effects on pharmacological and behavioural outcomes.

Pericytes mediate neurovascular remodeling in chronic arterial hypertension
Chronic arterial hypertension restructures the vascular architecture of the brain, leading to a series of pathological responses that culminate in cerebral small vessel disease. Pericytes respond dynamically to vascular challenges; however, how they manifest under the continuous strain of hypertension has not been elucidated. Therefore, in this study, we characterized pericyte behavior alongside hypertensive states in the spontaneously hypertensive stroke-prone rat (SHRSP) model, emphasizing their phenotypic and metabolic transformation. Our results reveal an early transition in PDGFR{beta}+ pericytes toward increased NG2 and CD13 co-expressing subtypes, signaling enhanced pericyte reactivity in an effort to stabilize vascular structures and an inflammatory engagement within the vascular niche in response to hypertensive stress. Gene expression profiling of microvessels revealed altered expression within crucial pathways i.e., angiogenesis, blood-brain barrier integrity, hypoxia and inflammation. Furthermore, we detected that circulating extracellular vesicles from SHRSP alter pericyte mitochondrial membrane potential, highlighting their ability to transmit pathogenic signals that exacerbate vascular remodeling. Detailed metabolic analysis revealed a significant shift toward glycolytic metabolism in pericytes already in initial hypertension, alongside a dysregulation of ATP production pathways. These findings emphasize the transformative influence of hypertension on cerebral pericytes and the extensive consequences on cerebral vascular health.