bioRxiv Subject Collection: Neuroscience's Journal

Amygdala TDP-43 pathology is associated with behavioural dysfunction and ferritin accumulation in amyotrophic lateral sclerosis.
Background: Cognitive and behavioural symptoms associated with amyotrophic lateral sclerosis and frontotemporal spectrum disorders (ALSFTSD) are thought to be driven, at least in part, by the pathological accumulation of TDP-43. Methods: Here we examine post-mortem tissue from six brain regions associated with cognitive and behavioural symptoms in a cohort of 30 people with sporadic ALS (sALS), a proportion of which underwent standardized neuropsychological behavioural assessment as part of the Edinburgh Cognitive ALS Screen (ECAS). Results: Overall, the behavioural screen performed as part of the ECAS predicted accumulation of pathological phosphorylated TDP-43 (pTDP-43) with 100% specificity and 86% sensitivity in behaviour-associated brain regions. Notably, of these regions, pathology in the amygdala was the most predictive correlate of behavioural dysfunction in sALS. In the amygdala of sALS patients, we show variation in morphology, cell type predominance, and severity of pTDP-43 pathology. Further, we demonstrate that the presence and severity of intra-neuronal pTDP-43 pathology, but not astroglial pathology, or phosphorylated Tau pathology, is associated with behavioural dysfunction. Cases were also evaluated using a TDP-43 aptamer (TDP-43APT), which revealed that pathology was not only associated with behavioural symptoms, but also with ferritin levels, a measure of brain iron. Conclusions: Intra-neuronal pTDP-43 and cytoplasmic TDP-43APT pathology in the amygdala is associated with behavioural symptoms in sALS. TDP-43APT staining intensity is also associated with increased ferritin, regardless of behavioural phenotype, suggesting that ferritin increases may occur upstream of clinical manifestation, in line with early TDP-43APT pathology, representing a potential region-specific imaging biomarker of early disease in ALS.

Compensating functional connectivity changesdue to structural connectivity damage viamodifications of local dynamics
Neurological pathologies as e.g. Alzheimer's Disease or Multiple Sclerosis are often associated to neurodegenerative processes affecting the strength and the transmission speed of long-range inter-regional fiber tracts. Such degradation of Structural Connectivity impacts on large-scale brain dynamics and the associated Functional Connectivity, eventually perturbing network computations and cognitive performance. Functional Connectivity however is not bound to merely mirror Structural Connectivity, but rather reflects the complex coordinated dynamics of many regions. Here, using analytical characterizations of toy models and computational simulations connectome-base whole-brain models, we predict that suitable modulations of regional dynamics could precisely compensate for the effects of structural degradation, as if the original Structural Connectivity strengths and speeds of conduction were effectively restored. The required dynamical changes are widespread and aspecific (i.e. they do not need to be restricted to specific regions) so that they could be potentially implemented via neuromodulation or pharmacological therapy, globally shifting regional excitability and/or excitation/inhibition balance. Computational modelling and theory thus suggest that, in the future therapeutic interventions could be designed to "repair brain dynamics" rather than structure to boost functional connectivity without having to block or revert neurodegenerative processes.

Targeting complement C3a receptor resolves mitochondrial hyperfusion and subretinal microglial activation in progranulin-deficient frontotemporal dementia
Mutations in progranulin (GRN) cause frontotemporal dementia (GRN-FTD) due to deficiency of the pleiotropic protein progranulin. GRN-FTD exhibits diverse pathologies including lysosome dysfunction, lipofuscinosis, microgliosis, and neuroinflammation. Yet, how progranulin loss causes disease remains unresolved. Here, we report that non-invasive retinal imaging of GRN-FTD patients revealed deficits in photoreceptors and the retinal pigment epithelium (RPE) that correlate with cognitive decline. Likewise, Grn-/- mice exhibit early RPE dysfunction, microglial activation, and subsequent photoreceptor loss. Super-resolution live imaging and transcriptomic analyses identified RPE mitochondria as an early driver of retinal dysfunction. Loss of mitochondrial fission protein 1 (MTFP1) in Grn-/- RPE causes mitochondrial hyperfusion and bioenergetic defects, leading to NFkB-mediated activation of complement C3a-C3a receptor signaling, which drives further mitochondrial hyperfusion and retinal inflammation. C3aR antagonism restores RPE mitochondrial integrity and limits subretinal microglial activation. Our study identifies a previously unrecognized mechanism by which progranulin modulates mitochondrial integrity and complement-mediated neuroinflammation.

Symmetry and Generalization in Local Learning of Predictive Representations
It is an increasingly accepted view that the representations which the brain generates are not merely descriptive of the current state of the world; rather, representations serve a predictive purpose. In spatial cognition, the Successor Representation (SR) from reinforcement learning provides a compelling candidate of how such predictive representations are used to encode space, in particular, hippocampal place cells are assumed to encode the SR. Here, we investigate how varying the temporal symmetry in learning rules influences those representations. To this end, we use a simple local learning rule which can be made insensitive to the temporal order. We analytically find that a symmetric learning rule results in a successor representation under a symmetrized version of the experienced transition structure. We then apply this rule to a two-layer neural network model loosely resembling hippocampal subfields CA3 - with a symmetric learning rule and recurrent weights - and CA1 - with an asymmetric learning rule and no recurrent weights. Here, when exposed repeatedly to a linear track, CA3 neurons in our model show less shift of the centre of mass than those in CA1, in line with existing empirical findings - an effect which is not observed using an asymmetric learning rule. We furthermore investigate the functional benefit of such representations in simple RL navigation tasks. Here, we find that using a symmetric learning rule yields representations which afford better generalization, when a model is probed to navigate to a new target without relearning the SR. This effect is reversed when the state space is not symmetric anymore. Thus, our results hint at a potential benefit of the inductive bias afforded by symmetric learning rules in areas employed in spatial navigation, where there naturally is a symmetry in the state space. In conclusion, we expand the SR theory of hippocampus by including symmetry in SR learning, which might yield an advantageous inductive bias for learning in space.

The correct temporal connectivity of the DG CA3 circuits involved in declarative memory processes depends on Vangl2-dependent planar cell polarity signaling
In the hippocampus, dentate gyrus granule cells connect to CA3 pyramidal cells via their axons, the mossy fibers (Mf). The synaptic terminals of Mfs (Mf boutons, MfBs) form large and complex synapses with thorny excrescences (TE) on the proximal dendrites CA3 pyramidal cells (PCs). MfB/TE synapses have distinctive "detonator" properties due to low intitial release probability and large presynaptic facilitation. The molecular mechanisms shaping the morpho-functional properties of MfB/TE synapses are still poorly understood, though alterations in their morphology are associated with Down syndrome, intellectual disabilities, and Alzheimer's disease. Here, we identify the core PCP gene Vangl2 as essential to the morphogenesis and function of MfB/TE synapsess. Vangl2 colocalises with the presynaptic heparan sulfate proteoglycan glypican 4 (GPC4) to stabilise the postsynaptic orphan receptor GPR158. Embryonic loss of Vangl2 disrupts the morphology of MfBs and TEs, impairs ultrastructural and molecular organisation, resulting in defective synaptic transmission and plasticity. In adult, the early loss of Vangl2 results in a number of hippocampus-dependent memory deficits including characteristic flexibility of declarative memory, organisation and retention of working/everyday-like memory. These deficits also lead to abnormal generalisation of memories to salient cues and diminished ability to form detailed contextual memories. Together, these results establish Vangl2 as a key regulator of DG-CA3 connectivity and functions.

Fully Human Bifunctional Intrabodies Achieve Graded Reduction of Intracellular Tau and Rescue Survival of MAPT Mutation iPSC-derived Neurons
Tau protein aggregation is a hallmark of several neurodegenerative diseases, including Alzheimers disease, frontotemporal dementia (FTD) and progressive supranuclear palsy (PSP), spurring development of tau-lowering therapeutic strategies. Here, we report fully human bifunctional anti-tau-PEST intrabodies that bind the mid-domain of tau to block aggregation and degrade tau via the proteasome using the ornithine decarboxylase (ODC) PEST degron. They effectively reduced tau protein in human iPSC-derived cortical neurons in 2D cultures and 3D organoids, including those with the disease-associated tau mutations R5L, N279K, R406W, and V337M. Anti-tau-hPEST intrabodies facilitated efficient ubiquitin-independent proteolysis, in contrast to tau-lowering approaches that rely on the cells ubiquitination system. Importantly, they counteracted the proteasome impairment observed in V337M patient-derived cortical neurons and significantly improved neuronal survival. By serial mutagenesis, we created variants of the PEST degron that achieved graded levels of tau reduction. Moderate reduction was as effective as high reduction against tau V337M-induced neural cell death.

Cardiometabolic state links neurovascular burden with brain structure and function across age: evidence from EEG and MRI
Aging affects brain structure and function alongside metabolic and vascular processes leading to energetic impairments. While local neurometabolic dysfunction in aging is well-documented, the influence of systemic cardiometabolic and vascular markers on brain structure and function remains less understood. We examine the link between cardiometabolic dysfunction (measured by an allostatic load index) and neurovascular burden (measured by white matter hyperintensities) with brain changes, including ventricular and hippocampal volume, as well as EEG activity, across age. Analyzing data from 196 healthy individuals across age (20-75 years), we found a significant positive correlation between allostatic load index and white-matter hyperintensities, irrespective of age. White matter hyperintensities are also positively linked with ventricular enlargement, but not hippocampal atrophy. The allostatic load index mediated the relationship between white-matter hyperintensities and ventricular volume. Regarding brain function, changes in the spectral aperiodic exponent but not periodic alpha power were linked to white matter hyperintensities and the allostatic load index. Such index mediated the relationship between spectral aperiodic exponent and white matter hyperintensities. Thus, findings suggest that the cardiometabolic state, as measured by an allostatic load index, plays a crucial role in brain health across age, particularly influencing ventricular enlargement and increased aperiodic activity.

It only takes seconds for a human monoclonal autoantibody to inhibit N-methyl-D-aspartate receptors
Transfer of autoantibodies targeting ionotropic N-methyl-D-aspartate receptors in autoimmune encephalitis patients into mice leads to typical disease signs. The long-term effects of receptor internalization significantly influence the antibody response. In this study, we focus on the direct and immediate impact of a specific patient's autoantibody on the function of N-methyl-D-aspartate receptors. We performed cell-attached single-channel recordings in human embryonic kidney cells transfected with the GluN1 and GluN2A subunit of the N-methyl-D-aspartate receptor. We investigated the direct effects of a specific and well-characterized monoclonal patient autoantibody (immunoglobulin G #003-102) against the amino-terminal domain of the glycine-binding GluN1 subunit of the receptors. Immunoglobulin G #003-102 reduced simultaneous receptor openings significantly compared to the control immunoglobulin G at both low and high glutamate and glycine concentrations. Upon closer examination of our data in 50-second to 2-second intervals, it is evident that the presence of autoantibodies results in a rapid decrease in the number of open receptors. On the other hand, the presence of antigen-binding fragments of immunoglobulin G #003-102 did not reduce the receptor openings. In conclusion, monoclonal immunoglobulin G #003-102 inhibits N-methyl-D-aspartate receptors rapidly and directly before receptor internalization occurs. The corresponding antigen-binding fragments did not alter the channel activity, indicating that the entire immunoglobulin G is necessary for the acute inhibitory effect. These results suggest an application of the antigen-binding fragments of #003-102 as a potential new treatment strategy for shielding the pathogenic epitopes on the N-methyl-D-aspartate receptors.

Injury distance limits the transcriptional response to spinal injury
The ability of neurons to sense and respond to damage is fundamental to homeostasis and nervous system repair. For some cell types, notably dorsal root ganglia (DRG) and retinal ganglion cells (RGCs), extensive profiling has revealed a large transcriptional response to axon injury that determines survival and regenerative outcomes. In contrast, the injury response of most supraspinal cell types, whose limited regeneration constrains recovery from spinal injury, is mostly unknown. Here we employed single-nuclei sequencing in mice to profile the transcriptional responses of diverse supraspinal cell types to spinal injury. Surprisingly, thoracic spinal injury triggered only modest changes in gene expression across all populations, including corticospinal tract (CST) neurons. Moreover, CST neurons also responded minimally to cervical injury but much more strongly to intracortical axotomy, including upregulation of numerous regeneration and apoptosis-related transcripts shared with injured DRG and RGC neurons. Thus, the muted response of CST neuron to spinal injury is linked to the injury's distal location, rather than intrinsic cellular characteristics. More broadly, these findings indicate that a central challenge for enhancing regeneration after a spinal injury is the limited sensing of distant injuries and the subsequent modest baseline neuronal response.

Generating human AMN and cALD iPSC-derived astrocytes with potential for modeling X-linked adrenoleukodystrophy phenotypes
X-adrenoleukodystrophy (X-ALD) is a peroxisomal metabolic disorder caused by mutations in the ABCD1 gene encoding the peroxisomal ABC transporter adrenoleukodystrophy protein (ALDP). Similar mutations in ABCD1 may result in a spectrum of phenotypes in males with slow progressing adrenomyeloneuropathy (AMN) and fatal cerebral adrenoleukodystrophy (cALD) dominating the majority of cases. Mouse model of X-ALD does not capture the phenotype differences and an appropriate model to investigate mechanism of disease onset and progress remains a critical need. Induced pluripotent stem cell (iPSC)-derived and cell models derived from them have provided useful tools for investigating cell-type specific disease mechanisms. Here, we generated induced pluripotent stem cell (iPSC) lines from skin fibroblasts of two each of apparently healthy control, AMN and cALD patients with non-integrating mRNA-based reprogramming. iPSC lines expanded normally and expressed pluripotency markers OCT4, SOX2, NANOG, SSEA and TRA-1-60. Expression of markers SOX17, brachyury, Desmin, OXT2 and beta tubulin III demonstrated the ability of the iPSCs to differentiate into all three germ layers. iPSC-derived lines from CTL, AMN and cALD male patients were differentiated into astrocytes. Differentiated AMN and cALD astrocytes lacked ABCD1 expression and accumulated VLCFA, a hallmark of X-ALD. These patient astrocytes provide disease-relevant tools to investigate mechanism of differential neuroinflammatory response and metabolic reprogramming in X-ALD. Further these patient-derived human astrocyte cell models will be valuable for testing new therapeutics.

Investigating visuo-tactile mirror properties in Borderline Personality Disorder: a TMS-EEG study
Patients with Borderline Personality Disorder (pw-BPD) are characterized by lower levels of cognitive empathy compared to healthy controls (HCs), indicating difficulties in understanding others' perspective. A candidate neural mechanism subtending empathic abilities is represented by the Tactile Mirror System (TaMS), which refers to mirror-like mechanisms in the somatosensory cortices. However, little is known about TaMS alterations in BPD, specifically in terms of brain connectivity within this network. Here, we aimed at providing novel insights on TaMS as neurophysiological candidate for BPD empathic deficits, with a special focus on TaMS connectivity by means of the combined use of transcranial magnetic stimulation and electroencephalography (TMS-EEG). Twenty pw-BPD and 20 HCs underwent a thorough investigation: we collected measures of empathic abilities obtained from self-report questionnaires, behavioral performance in a visuo-tactile spatial congruency task, and TMS-evoked potentials (TEPs) as effective connectivity indexes. In the TMS-EEG session, TMS was delivered over the right primary somatosensory cortex (S1) following the presentation of real touches and visual touches, while 74-channel EEG was continuously recorded. In the visuo-tactile spatial congruency task and the TMS-EEG recording, control conditions with visual touches on objects instead of body parts enabled to disentangle the involvement of TaMS from non-specific effects. The study is the first one employing TMS-EEG in pw-BPD and it has been preregistered before data collection. Consistent with previous findings, results show that pw-BPD reported significantly lower levels of cognitive empathy. Moreover, pw-BPD made significantly more errors than controls in the visuo-tactile spatial congruency task during visual touches on human body parts and not on objects. Finally, pw-BPD displayed a different connectivity pattern from S1-TEPs that was not specific for TaMS: they showed a lower P60 component during touch observation, as well as reduced amplitude of later TEPs responses (after ~100 ms) during real touches. Overall, the present study shows behavioral evidence of TaMS impairment and a more general alteration in the connectivity pattern of the somatosensory network in pw-BPD.

Reuniens thalamus recruits recurrent excitation in medial prefrontal cortex.
Medial prefrontal cortex (mPFC) and hippocampus are critical for memory retrieval, decision making and emotional regulation. While ventral CA1 (vCA1) shows direct and reciprocal connections with mPFC, dorsal CA1 (dCA1) forms indirect pathways to mPFC, notably via the thalamic Reuniens nucleus (Re). Neuroanatomical tracing has documented structural connectivity of this indirect pathway through Re however, its functional operation is largely unexplored. Here we used in vivo and in vitro electrophysiology along with optogenetics to address this question. Whole-cell patch-clamp recordings in acute mouse brain slices revealed both monosynaptic excitatory responses and disynaptic feedforward inhibition for both Re-mPFC and Re-dCA1 pathways. However, we also identified a novel biphasic excitation of mPFC by Re, but not dCA1. These early monosynaptic and late recurrent components are in marked contrast to the primarily feedforward inhibition characteristic of thalamic inputs to neocortex. Local field potential recordings in mPFC brain slices revealed that this biphasic excitation propagates throughout all cortical lamina, with the late excitation specifically enhanced by GABAAR blockade. In vivo Neuropixels recordings in head-fixed awake mice revealed a similar biphasic excitation of mPFC units by Re activation. In summary, Re output produces recurrent feed-forward excitation within mPFC suggesting a potent amplification system in the Re-mPFC network. This may facilitate amplification of dCA1->mPFC signals for which Re acts as the primary conduit, as there is little direct connectivity. In addition, the capacity of mPFC neurons to fire bursts of action potentials in response to Re input suggests that these synapses have a high gain.

Embodied decisions as active inference
Decision-making is often conceptualized as a serial process, during which sensory evidence is accumulated for the choice alternatives until a certain threshold is reached, at which point a decision is made and an action is executed. This decide-then-act perspective has successfully explained various facets of perceptual and economic decisions in the laboratory, in which action dynamics are usually irrelevant to the choice. However, living organisms often face another class of decisions - called embodied decisions - that require selecting between potential courses of actions to be executed timely in a dynamic environment, e.g., for a lion, deciding which gazelle to chase and how fast to do so. Studies of embodied decisions reveal two aspects of goal-directed behavior in stark contrast to the serial view. First, that decision and action processes can unfold in parallel; second, that action-related components, such as the motor costs associated with the choice alternatives and required to "change mind'' between them, exert a feedback effect on the decision taken. Here, we show that these signatures of embodied decisions emerge naturally in active inference - a framework that simultaneously optimizes perception and action, according to the same (free energy minimization) imperative. We show that optimizing embodied choices requires a continuous feedback loop between motor planning (where beliefs about choice alternatives guide action dynamics) and motor inference (where action dynamics finesse beliefs about choice alternatives). Furthermore, our active inference simulations reveal the normative character of embodied decisions in ecological settings - namely, achieving an effective balance between a high accuracy and a low risk of losing valid opportunities.

TDP-43 pathology is sufficient to drive axon initial segment plasticity and hyperexcitability of spinal motoneurones in vivo in the TDP43-NLS model of Amyotrophic Lateral Sclerosis
A hyperexcitability of the motor system is consistently observed in Amyotrophic Lateral Sclerosis (ALS) and has been implicated in the disease pathogenesis. What drives this hyperexcitability in the vast majority of patients is unknown. This is important to know as existing treatments simply reduce all neuronal excitability and fail to distinguish between pathological changes and important homeostatic changes. Understanding what drives the initial pathological changes could therefore provide better treatments. One challenge is that patients represent a heterogeneous population and the vast majority of cases are sporadic. One pathological feature that almost all (~97%) cases (familial and sporadic) have in common is cytoplasmic aggregates of the protein TDP-43 which is normally located in the nucleus. In our experiments we investigated whether this pathology was sufficient to increase neuronal excitability and the mechanisms by which this occurs. We used the TDP-43({Delta}NLS) mouse model which successfully recapitulates this pathology in a controllable way. We used in vivo intracellular recordings in this model to demonstrate that TDP-43 pathology is sufficient to drive a severe hyper-excitability of spinal motoneurones. Reductions in soma size and a lengthening and constriction of axon initial segments were observed, which would contribute to enhanced excitability. Resuppression of the transgene resulted in a return to normal excitability parameters by 6-8 weeks. We therefore conclude that TDP-43 pathology itself is sufficient to drive a severe but reversible hyperexcitability of spinal motoneurones.

Low-invasive, wide-field, and cellular resolution two-photon imaging of neural population activity in brainstem and nucleus tractus solitarii
Brain-viscera communication is thought to play a crucial role in regulating mental health, with the vagus nerve being a key structure mediating this interaction. Clinically, artificial vagus nerve stimulation (VNS) is used to treat various neuropsychiatric disorders, highlighting the importance of vagal afferent fibers in regulating emotion. The nucleus tractus solitarii (NTS) is a brainstem structure proposed to receive direct signals from vagal afferents and relay them to the brain emotional regulatory networks. Direct evidence for this network is limited, however, due to the anatomic complexity and difficulty accessing the deep-brain NTS region in living animals. Here, to investigate this further, we developed a wide-field and deep-brain two-photon imaging method using a prism-based optical interface enabling the identification of cellular-resolution neural activities of the NTS while keeping the cerebellum, which covers the NTS, intact. This method allowed us to evaluate how NTS neurons respond to VNS and the gastrointestinal hormone cholecystokinin-8, suggesting its usefulness for investigating the role of the vagus-NTS pathway in regulating emotion.

Prediction of future input explains lateral connectivity in primary visual cortex
Neurons in primary visual cortex (V1) show a remarkable functional specificity in their pre- and postsynaptic partners. Recent work has revealed a variety of wiring biases describing how the short- and long-range connections of V1 neurons relate to their tuning properties. However, it is less clear whether these connectivity rules are based on some underlying principle of cortical organization. Here, we show that the functional specificity of V1 connections emerges naturally in a recurrent neural network optimized to predict upcoming sensory inputs for natural visual stimuli. This temporal prediction model reproduces the complex relationships between the connectivity of V1 neurons and their orientation and direction preferences, the tendency of highly connected neurons to respond more similarly to natural movies, and differences in the functional connectivity of excitatory and inhibitory V1 populations. Together, these findings provide a principled explanation for the functional and anatomical properties of early sensory cortex.

Fibroblasts carrying intermediate C9orf72 hexanucleotide repeat expansions from iNPH patients show impaired energy metabolism but no cell pathologies
Long C9orf72 hexanucleotide repeat expansions (C9-HRE) are the most common genetic cause of frontotemporal dementia (FTD), a group of neurodegenerative syndromes leading to cognitive dysfunction and frontal and temporal atrophy. FTD is a potential comorbidity of idiopathic normal pressure hydrocephalus (iNPH) and carrying the C9-HRE can modify the age-of-onset in iNPH patients. While intermediate-length C9-HRE (<30 repeats) are often considered non-pathogenic, the exact pathological cutoff is unclear. In this study, we assessed whether fibroblasts from iNPH patients carrying intermediate C9-HRE display C9 HRE-associated pathological hallmarks and changes in cellular function. C9-HRE-associated RNA foci were not detected in the intermediate carriers. The number of p62-positive puncta was significantly increased only in long C9-HRE carrier fibroblasts, in line with p62-positive intracellular inclusions observed in a brain biopsy from the patient. Specific parameters of mitochondrial respiration were significantly reduced in both the long and intermediate C9-HRE carrier fibroblasts. Fibroblasts from the intermediate C9-HRE carriers showed upregulated glycolytic activity, possibly to counteract the reduced mitochondrial respiration, which could not be observed in the long C9-HRE carriers. In conclusion, these data suggest that while the long C9-HRE leads to more severe cellular pathologies than intermediate C9-HRE, the latter might predispose cells to pathological changes.

Interference underlies attenuation upon relearning in sensorimotor adaptation
Savings refers to the gain in performance upon relearning a task. In sensorimotor adaptation, savings is tested by having participants adapt to perturbed feedback and, following a washout block during which the system resets to baseline, presenting the same perturbation again. While savings has been observed with these tasks, we have shown that the contribution from implicit sensorimotor adaptation, a process that uses sensory prediction errors to recalibrate the sensorimotor map, is actually attenuated upon relearning (Avraham et al., 2021). In the present study, we test the hypothesis that this attenuation is due to interference arising from the washout block, and more generally, from experience with a different relationship between the movement and the feedback. In standard adaptation studies, removing the perturbation at the start of the washout block results in a salient error signal in the opposite direction to that observed during learning. As a starting point, we replicated the finding that implicit adaptation is attenuated following a washout period in which the feedback now signals a salient opposite error. When we eliminated visual feedback during washout, implicit adaptation was no longer attenuated upon relearning, consistent with the interference hypothesis. Next, we eliminated the salient error during washout by gradually decreasing the perturbation, creating a scenario in which the perceived errors fell within the range associated with motor noise. Nonetheless, attenuation was still prominent. Inspired by this observation, we tested participants with an extended experience with veridical feedback during an initial baseline phase and found that this was sufficient to cause robust attenuation of implicit adaptation during the first exposure to the perturbation. This effect was context-specific: It did not generalize to movements that were not associated with the interfering feedback. Taken together, these results show that the implicit sensorimotor adaptation system is highly sensitive to memory interference from a recent experience with a discrepant action-outcome contingency.

Molecular and functional alterations in the cerebral microvasculature in an optimized mouse model of sepsis-associated cognitive dysfunction.
Systemic inflammation has been implicated in the development and progression of neurodegenerative conditions such as cognitive impairment and dementia. Recent clinical studies indicate an association between sepsis, endothelial dysfunction, and cognitive decline. However, the investigations of the role and therapeutic potential of the cerebral microvasculature in systemic inflammation-induced cognitive dysfunction have been limited by the lack of standardized experimental models for evaluating the alterations in the cerebral microvasculature and cognition induced by the systemic inflammatory response. Herein, we validated a mouse model of endotoxemia that recapitulates key pathophysiology related to sepsis-induced cognitive dysfunction, including the induction of an acute systemic hyperinflammatory response, blood-brain barrier (BBB) leakage, neurovascular inflammation, and memory impairment after recovery from the systemic inflammatory response. In the acute phase, we identified novel molecular (e.g. upregulation of plasmalemma vesicle associated protein, a driver of endothelial permeability, and the pro-coagulant plasminogen activator inhibitor-1, PAI-1) and functional perturbations (i.e., albumin and small molecule BBB leakage) in the cerebral microvasculature along with neuroinflammation. Remarkably, small molecule BBB permeability, elevated levels of PAI-1, intra/perivascular fibrin/fibrinogen deposition and microglial activation persisted 1 month after recovery from sepsis. We also highlight molecular neuronal alterations of potential clinical relevance following systemic inflammation including changes in neurofilament phosphorylation and decreases in postsynaptic density protein 95 and brain-derived neurotrophic factor suggesting diffuse axonal injury, synapse degeneration and impaired neurotrophism. Our study serves as a standardized model to support future mechanistic studies of sepsis-associated cognitive dysfunction and to identify novel endothelial therapeutic targets for this devastating condition.

Oligodendrocyte precursor cells exacerbate acute CNS inflammation via macrophage and T cell activation in a mouse model of multiple sclerosis
Oligodendrocyte precursor cells (OPCs) are a type of glial cell that differentiates into mature oligodendrocytes, a cell type that contributes to myelination, but their roles in the pathologies are not fully understood. Activities other than differentiation into oligodendrocytes have recently been reported for OPCs present in the inflammatory milieu, but intervention studies using animal models are lacking. This study aimed to explore the role of OPCs in mouse MS model experimental autoimmune encephalomyelitis (EAE). Using inducible diphtheria toxin receptor-expressing transgenic mice, platelet-derived growth factor receptor A (PDGFR)+ OPCs were depleted in EAE mice. Surprisingly, OPC depletion in the acute phase improved clinical scores and reduced demyelination. Major histocompatibility complex (MHC) class II was reduced in the spinal cord, whereas astrocyte marker and blood-spinal cord barrier tight junction and adhesion molecule expressions were unaffected after OPC depletion. The numbers of T cells and IL17-expressing Th17 cells were decreased in the spinal cords of the OPC-depleted group. MHC class II expression in spinal cord macrophages was consistently decreased by OPC depletion. These data suggest that in the acute phase of EAE, OPCs are involved in activation of infiltrated macrophages and induce subsequent T cell activation and neuroinflammation. Although the precise mechanisms remain unclear, this implies that OPCs exist not only as the source for oligodendrocytes but also play a pivotal role in central nervous system (CNS) autoimmune inflammation.

Shape-Biased Learning by Thinking Inside the Box
Deep Neural Networks (DNNs) may surpass human-level performance on vision tasks such as object recognition and detection, but their model behavior still differs from human behavior in important ways. One prominent example of this difference, and the main focus of our paper, is that DNNs trained on ImageNet exhibit an object texture bias, while humans are consistently biased towards shape. DNN shape-bias can be increased by data augmentation, but next to being computationally more expensive, data augmentation is a biologically implausible method of creating texture-invariance. We present an empirical study on texture-shape-bias in DNNs showcasing that high texture-bias correlates with high background-object ratio. In addition, DNNs trained on tight object bounding boxes of ImageNet images are substantially more biased towards shape than models trained on the full images. Using a custom dataset of high-resolution, object annotated scene images, we show that (I) shape-bias systematically varies with training on bounding boxes, (II) removal of global object shape as a result of commonly applied cropping during training increases texture bias, (III) shape-bias is negatively correlated with test accuracy on ImageNet while being positively correlated on cue-conflict images created using bounding boxes, following the trend of humans. Overall, we show that an improved supervision signal that better reflects the visual features that truly belong to the to-be-classified object increases the shape-bias of deep neural networks. Our results also imply that simultaneous human alignment on both classification accuracy and strategy can not be achieved on default ImageNet images, suggesting the need for new assessments of both shape-bias and behavioural alignment between DNNs and humans.

Identification of Recurrent Dynamics in Distributed Neural Populations
Large-scale recordings of neural activity over broad anatomical areas with high spatial and temporal resolution are increasingly common in modern experimental neuroscience. Recently, recurrent switching dynamical systems have been used to tackle the scale and complexity of these data. However, an important challenge remains in providing insights into the existence and structure of recurrent linear dynamics in neural time series data. Here we test a scalable approach to time-varying autoregression with low-rank tensors to recover the recurrent dynamics in stochastic neural mass models with multiple stable attractors. We demonstrate that the sparse representation of time-varying system matrices in terms of temporal modes can recover the attractor structure of simple systems via clustering. We then consider simulations based on a human brain connectivity matrix in high and low global connection strength regimes, and reveal the hierarchical clustering structure of the dynamics. Finally, we explain the impact of the forecast time delay on the estimation of the underlying rank and temporal variability of the time series dynamics. This study illustrates that prediction error minimization is not sufficient to recover meaningful dynamic structure and that it is crucial to account for the three key timescales arising from dynamics, noise processes, and attractor switching.

Multiscale Modes of Functional Brain Connectivity
Information processing in the brain spans from localised sensorimotor processes to higher-level cognition that integrates across multiple regions. Interactions between and within these subsystems enable multiscale information processing. Despite this multiscale characteristic, functional brain connectivity is often either estimated based on 10-30 distributed modes or parcellations with 100-1000 localised parcels, both missing across-scale functional interactions. We present Multiscale Probabilistic Functional Modes (mPFMs), a new mapping which comprises modes over various scales of granularity, thus enabling direct estimation of functional connectivity within- and across-scales. Crucially, mPFMs emerged from data-driven multilevel Bayesian modelling of large functional MRI (fMRI) populations. We demonstrate that mPFMs capture both distributed brain modes and their co-existing subcomponents. In addition to validating mPFMs using simulations and real data, we show that mPFMs can predict ~900 personalised traits from UK Biobank more accurately than current standard techniques. Therefore, mPFMs can offer a paradigm shift in functional connectivity modelling and yield enhanced fMRI biomarkers for traits and diseases.

Anterior insular activity signals perceptual conflicts induced by temporal and spatial context
The signals registered by our senses are inherently ambiguous. Subjective experience, by contrast, is informative: it portrays one interpretation of the sensory environment at a time while discarding competing alternatives. This is exemplified by bistable perception, where ambiguous sensory information induces prolonged intervals of alternating unambiguous perceptual states. According to predictive-processing accounts of bistable perception, perceptual experiences in the recent past constitute a predictive context that stabilizes perception, while sensory information that is in conflict with this predictive context evokes prediction errors. These prediction errors are thought to drive spontaneous perceptual switches. We asked whether this mechanism generalizes to conflicts between other forms of predictive context and sensory information. To this aim, we investigated the neural correlates of perceptual conflicts with temporal and spatial context during bistable perception using functional magnetic resonance imaging (fMRI). Twenty-six healthy participants viewed serial presentations of ambiguous structure-from-motion stimuli either in isolation (conflict with temporal context) or embedded in a similar but unambiguous surround stimulus (conflict with spatial context). The neural correlates of conflicts with temporal and spatial context overlapped in the anterior insula bilaterally. Model-based analyses similarly yielded common prediction error signals in the anterior insula bilaterally, right inferior frontal gyrus and right inferior parietal lobe. Together, these findings point to a generic role of these frontoparietal regions in detecting perceptual conflict and thus in the construction of unambiguous perceptual experiences.

Geometric Study of Human Binocular Vision with Misaligned Eye Optics
The brain uses two slightly different 2D retinal images to enhance our vision with stereopsis, i.e., spatial depth and 3D shape. Stereopsis is organized by pairs of corresponding retinal elements of zero disparity: a small retinal area in one eye and the corresponding unique area in the other share one subjective visual direction. This organization results in retinal disparity's spatial coordinates, i.e., the iso-disparity curves. However, stereopsis studies have overlooked the misalignment of the healthy human eye's optical components. This study presents comprehensive geometric constructions in the binocular system, with the eye model incorporating the fovea that is not located on and the lens that is tilted away from the eye's optical axis. It includes the vertical misalignment of optical components and the 3D binocular field of fixations with previously considered horizontal misalignment underlying stereopsis. When the eyes' binocular posture changes, 3D spatial coordinates of the retinal disparity (iso-disparity curves) and the subjective vertical horopter transformations are visualized in GeoGebra's dynamic geometry environment. Rodrigues' vector framework calculates the ocular torsion for each eye's posture. In addition to the well-known role of horizontal misalignment of the eye's optical components in the quality of vision and less-known role in the asymmetry of retinal corresponding elements, the consequences and functional roles of vertical misalignment are explained in the following finding: The classic Helmholtz theory, which states that the subjective vertical retinal meridian inclination to the retinal horizontal meridian explains the received backward tilt of the vertical horopter, is less relevant when the eye's optical components are misaligned. Instead, the lens vertical tilt provides the retinal vertical criterion that explains the experimentally measured vertical horopter's inclination.

Age associated alterations in the cortical representation of cardiac signals: A heartfelt tale
Neural responses to the cardiac rhythms, known as heartbeat evoked responses (HER), provides a unique avenue for investigating the interaction between the brain and the heart, pivotal for various physiological and cognitive functions. Age is recognised as a significant factor influencing this interaction, given its impact on both the structural and functional aspects of the brain and the cardiovascular system. However, the precise nature of this interaction during the healthy aging process remains elusive. To gain a deeper understanding, our objective in this study is to examine how the cardiac rhythms influences spontaneous brain rhythms by utilizing HER as a measure, alongside exploring the underlying networks across a healthy aging (N = 620; Female = 49.52%) cohort and to identify and characterize the workings of brain networks which prominently represents the HERs. We report that (1) HERs exhibit time-locked activity within the 180-320 ms post R-peak of the electrocardiogram (ECG) waveform and the amplitude of this evoked activity significantly decreases across lifespan aging for both the genders, 2) assessment of the mechanism behind HER shows the increasing inter-trial phase coherence (ITPC) values in the theta frequency band than altering the spectral power across the age (3) neural sources of HERs were source localized to the right orbitofrontal cortex, right anterior prefrontal cortex and left temporal pole (4) causal functional maps using using granger causality (GC) revealed bidirectional interactions between right orbitofrontal cortex and anterior frontal cortex, right orbitofrontal cortex and left temporal pole and unidirectional interaction between anterior prefrontal cortex to left temporal pole. Additionally, GC values showed an increase from left temporal pole to right orbitofrontal cortex and from right anterior prefrontal cortex to left temporal pole across age, indicating compensatory mechanisms in play to maintain homeostasis. Overall, these findings provide a comprehensive understanding of the interaction between heart and brain in healthy ageing and present opportunities to identify non-invasive markers for characterizing pathological development in neurological and cardiovascular functions.

Striosomes Target Nigral Dopamine-Containing Neurons via Direct-D1 and Indirect-D2 Pathways Paralleling Classic Direct-Indirect Basal Ganglia Systems
The classic output pathways of the basal ganglia are known as the direct-D1 and indirect-D2, or Go/No-Go, pathways. Balance of the activity in these canonical direct-indirect pathways is considered a core requirement for normal movement control, and their imbalance is a major etiologic factor in movement disorders including Parkinsons disease. We present evidence for a conceptually equivalent parallel system of direct-D1 and indirect-D2 pathways that arise from striatal projection neurons (SPNs) of the striosome compartment rather than from the matrix. These striosomal direct (S-D1) and indirect (S-D2) pathways, as a pair, target dopamine-containing neurons of the substantia nigra (SNpc) instead of the motor output nuclei of the basal ganglia. The novel anatomically and functionally distinct indirect-D2 striosomal pathway targets dopaminergic SNpc cells indirectly via a core region of the external pallidum (GPe). We demonstrate that these S-D1 and S-D2 pathways oppositely modulate striatal dopamine release in freely behaving mice under open-field conditions and oppositely modulate locomotor and other movements. These S-D1 and S-D2 pathways further exhibit different, time-dependent responses during performance of a probabilistic decision-making maze task and respond differently to rewarding and aversive stimuli. These contrasts depend on mediolateral and anteroposterior striatal locations of the SPNs as are the classic direct and indirect pathways. The effects of S-D1 and S-D2 stimulation on striatal dopamine release and voluntary locomotion are nearly opposite. The parallelism of the direct-indirect circuit design motifs of the striosomal S-D and S-D2 circuits and canonical matrix M-D1 and M-D2, and their contrasting behavioral effects, call for a major reformulation of the classic direct-indirect pathway model of basal ganglia function. Given that some striosomes receive limbic and association cortical inputs, the S-D1 and S-D2 circuits likely influence motivation for action and behavioral learning, complementing and possibly reorienting the motoric activities of the canonical matrix pathways. At a fundamental level, these findings suggest a unifying framework for aligning two sets of circuits that share the organizational motif of opponent D1 and D2 regulation, but that have different outputs and can even have opposite polarities in their targets and effects, albeit conditioned by striatal topography. Our findings further delineate a potentially therapeutically important set of pathways influencing dopamine, including a D2 receptor-linked S-D2 pathway likely unknowingly targeted by administration of many therapeutic drugs including those for Parkinsons disease. The novel parallel pathway model that we propose here could help to account for the normally integrated modulatory influence of the basal ganglia on motivation for actions as well as the actions themselves.

Contributions of action potentials to scalp EEG: theory and biophysical simulations
Differences in the apparent 1/f component of neural power spectra require correction depending on the underlying neural mechanisms, which remain incompletely understood. Past studies suggest that neuronal spiking produces broadband signals and shapes the spectral trend of invasive macroscopic recordings, but it is unclear to what extent action potentials (APs) influence scalp EEG. Here, we combined biophysical simulations with statistical modelling to examine the amplitude and spectral content of scalp potentials generated by the electric fields from spiking activity. We found that under physiological conditions, synchronized aperiodic spiking can account for at most 1% of the spectral density observed in EEG recordings, suggesting that the EEG spectral trend reflects only external noise at high frequencies. Indeed, by analyzing previously published data from pharmacologically paralyzed subjects, we confirmed that the EEG spectral trend is entirely explained by synaptic timescales and electromyogram contamination. We also investigated rhythmic EEG generation, finding that APs can generate narrowband power between approximately 60 and 600 Hz, thus reaching frequencies much faster than the timescales of excitatory synaptic currents. Our results imply that different spectral detrending strategies are required for high frequency oscillations compared to slower synaptically generated EEG rhythms.

Estrous phase during fear extinction modulates fear relapse through a nigrostriatal dopamine pathway
Elevated ovarian hormones during fear extinction can enhance fear extinction memory retention and reduce renewal, but the mechanisms remain unknown. Ovarian hormones modulate dopamine (DA) transmission, a key player in fear extinction. In males, stimulation of substantia nigra (SN) DA neurons during fear extinction reduces renewal; an effect mimicked by a DA D1 receptor agonist into the dorsolateral striatum (DLS). The current studies tested the role of the SN-DLS pathway in estrous cycle-modulation of fear extinction and relapse. In cycling female, Long-Evans rats, fear extinction during proestrus or estrus (Pro/Est; high hormones) resulted in less relapse (renewal and spontaneous recovery) compared to males or females in metestrus or diestrus (Met/Di; low hormones). This effect was mimicked by estradiol (E2) administration to ovariectomized rats. Females in Pro/Est had greater fear extinction-induced cFos within SN DA neurons compared to males. Similarly, fast scan cyclic voltammetry revealed that electrically-evoked DA release in the DLS is potentiated by E2 and is greater during Pro/Est compared to Met/Di. An inhibitory intersectional chemogenetic approach targeting the SN-DLS pathway suppressed electrically-evoked DA release in the DLS and restored fear renewal in females exposed to simultaneous fear extinction and SN-DLS inhibition during Pro/Est. Conversely, chemogenetic stimulation of the SN-DLS pathway during extinction reduced fear renewal in males. These data suggest that levels of ovarian hormones present during fear extinction modulate relapse through a SN-DLS pathway, and that the SN-DLS pathway represents a novel target for the reduction of fear relapse in both sexes.

Dynamic regulation of mRNA acetylation at synapses by learning and memory
N4-acetylcytidine (ac4C) is the only RNA acetylation modification identified in eukaryotes and has recently been recognized as an epitranscriptomic mechanism regulating mRNA stability and translation efficiency. However, the function and regulation of mRNA acetylation in the brain remain largely unknown. In this study, the presence of ac4C in mRNA was demonstrated by dot blot analysis and UPLC-MS/MS. A transcriptome-wide mapping of ac4C was performed in the hippocampus of adult mice trained in the Morris water maze, a protocol for learning and memory. Notably, the protein levels of N-acetyltransferase 10 (NAT10), the ac4C writer, increased at synapses following memory formation but returned to baseline levels after forgetting. Moreover, the downregulation of NAT10-mediated N4-acetylcytidine in mRNA in the mouse hippocampus using the Cre/LoxP strategy resulted in impaired synaptic plasticity and deficits in learning and memory. These findings underscore the dynamics and functions of synaptic mRNA acetylation during learning and memory, providing novel insights into the epitranscriptomic regulation of brain function. The ac4C epitranscriptome dataset in mouse hippocampus is accessible via the website (http://ac4Catlas.com/).

Evidence for direct control of neurovascular function by circulating platelets in healthy older adults
Platelets play a vital role in preventing haemorrhage through haemostasis, but complications arise when platelets become overly reactive, leading to pathophysiology such as atherothrombosis (1,2). Elevated haemostatic markers are linked to dementia (3) and predict its onset in long-term studies (4). Despite epidemiological evidence, the mechanism linking haemostasis with early brain pathophysiology remains unclear. Here, we aimed to determine whether a mechanistic association exists between platelet function and neurovascular function in 52 healthy mid- to older-age adults. To do this we combined, for the first time, magnetic resonance imaging (MRI) of neurovascular function, peripheral vascular physiology, and in vitro platelet assaying. We show a direct association between platelet reactivity and neurovascular function that is both independent of vascular reactivity and mechanistically specific: Distinct platelet signalling mechanisms (Adenosine 5'-diphosphate, Collagen-Related Peptide, Thrombin Receptor Activator Peptide 6) were directly associated with different physiological components of the haemodynamic response to neural (visual) stimulation (full-width half-maximum, time to peak, area under the curve), an association that was not mediated by peripheral vascular effects. This finding challenges the previous belief that systemic vascular health determines the vascular component of neurovascular function, highlighting a specific link between circulating platelets and the neurovascular unit. Since altered neurovascular function marks the initial stages of neurodegenerative pathophysiology (5), understanding this novel association becomes now imperative, with the potential to lead to a significant advancement in our comprehension of early dementia pathophysiology

Functional Complexity of Engineered Neural Networks Self-Organized on Novel 3D Interfaces
Engineered neural networks are indispensable tools for studying neural function and dysfunction in controlled microenvironments. In vitro, neurons self-organize into complex assemblies with structural and functional similarities to in vivo circuits. Traditionally, these models are established on planar interfaces, but studies suggest that the lack of a three-dimensional growth space affects neuronal organization and function. While methods supporting 3D growth exist, reproducible 3D neuroengineering techniques compatible with electrophysiological recording methods are still needed. In this study, we developed a novel biocompatible interface made of the polymer SU-8 to support 3D network development. Using electron microscopy and immunocytochemistry, we show that neurons utilize these 3D scaffolds to self-assemble into complex, multi-layered networks. Furthermore, interfacing the scaffolds with custom microelectrode arrays enabled characterizing of electrophysiological activity. Both planar control networks and 3D networks displayed complex interactions with integrated and segregated functional dynamics. However, control networks showed stronger functional interconnections, higher entropy, and increased firing rates. In summary, our interfaces provide a versatile approach for supporting neural networks with a 3D growth environment, compatible with assorted electrophysiology and imaging techniques. This system can offer new insights into the impact of 3D topologies on neural network organization and function.

Working memory performance predicts, but does not reduce, cocaine- and cannabinoid-seeking in adult male rats
Background: Cognitive deficits reflecting impaired executive function are commonly associated with psychiatric disorders, including substance use. Cognitive training is proposed to improve treatment outcomes for these disorders by promoting neuroplasticity within the prefrontal cortex, enhancing executive control, and mitigating cognitive decline due to drug use. Additionally, brain derived neurotrophic factor (BDNF) can facilitate plasticity in the prefrontal cortex and reduce drug-seeking behaviors. We investigated whether working memory training could elevate BDNF levels in the prefrontal cortex and if this training would predict or protect against cocaine or cannabinoid seeking. Methods: Adult male rats were trained to perform a 'simple' or 'complex' version of a delayed-match-to-sample working memory task. Rats then self-administered cocaine or the synthetic cannabinoid WIN55,212-2 and were tested for cued drug-seeking during abstinence. Tissue from the prefrontal cortex and dorsal hippocampus was analyzed for BDNF protein expression. Results: Training on the working memory task enhanced endogenous BDNF protein levels in the prelimbic prefrontal cortex but not the dorsal hippocampus. Working memory training did not impact self-administration of either drug but predicted the extent of WIN self-administration and cocaine seeking during abstinence. Conclusions: These results suggest that working memory training promotes endogenous BDNF but does not alter drug-seeking or drug-taking behavior. However, individual differences in cognitive performance prior to drug exposure may predict vulnerability to future drug use.

Sex Differences in Morphine Sensitivity of Neuroligin-3 Knockout Mice
Sex has a strong influence on the prevalence and course of brain conditions, including autism spectrum disorders. The mechanistic basis for these sex differences remains poorly understood, due in part to historical bias in biomedical research favoring analysis of male subjects, and the exclusion of female subjects. For example, studies of male mice carrying autism-associated mutations in neuroligin-3 are over-represented in the literature, including our own prior work showing diminished responses to chronic morphine exposure in male neuroligin-3 knockout mice. We therefore studied how constitutive and conditional genetic knockout of neuroligin-3 affects morphine sensitivity of female mice. In contrast to male mice, female neuroligin-3 knockout mice showed normal psychomotor sensitization after chronic morphine exposure. However, in the absence of neuroligin-3 expression, both female and male mice show a similar change in the topography of locomotor stimulation produced by morphine. Conditional genetic deletion of neuroligin-3 from dopamine neurons increased the locomotor response of female mice to high doses of morphine, contrasting with the decrease in psychomotor sensitization caused by the same manipulation in male mice. Together, our data reveal that knockout of neuroligin-3 has both common and distinct effects on morphine sensitivity in female and male mice. These results also support the notion that female sex can confer resilience against the impact of autism-associated gene variants.

Physiological Harmony or Discord? Unveiling the Correspondence Between Subjective Arousal, Valence and Physiological Responses
Although affective state may occur almost inevitably together with physiological changes, it is still unclear whether events evoking similar affective experiences also produce comparable physiological responses or whether variation is the norm within individuals. To unravel this debate, we investigated the correspondence between physiological reactions and experienced arousal and valence, using representational similarity analysis. In two independent (Ns = 491 and 64) samples and three affect-inducing tasks, representational similarity matrices (RSMs) of skin conductance (SCR) and startle responses, as readouts of arousal and valence, respectively, were compared to RSMs of valence and arousal ratings that align with these competing theories. Furthermore, to address the role of intraindividual variability, we also investigated its influence on the relationship between physiological responses and experienced affect. We observed that dismissing vs considering intraindividual variability led to differential relations with models of valence and arousal, but models assuming variation proofed to be more representative of individual physiological patterns. Importantly, we observed strong to decisive evidence for a correspondence between SCR and startle responses and models of arousal and valence that assume variation, especially between trials evoking higher amplitude responses. These results emphasize the importance of considering intraindividual variability to assess the affect-physiology relationship (and in psychophysiology research in general) and invite to reconsider the notion of physiological reactivity as a potential indicator of affective states, prompting a shift towards understanding the mechanisms through which physiological changes contribute to conscious affective experiences.

Different Emotional States Engage Distinct Descending Pathways from the Prefrontal Cortex
Emotion regulation, essential for adaptive behavior, depends on the brain's capacity to process a range of emotions. Current research has largely focused on individual emotional circuits without fully exploring how their interaction influences physiological responses or understanding the neural mechanisms that differentiate emotional valence. Using in vivo calcium imaging, electrophysiology, and optogenetics, we examined neural circuit dynamics in the medial prefrontal cortex (mPFC), targeting two key areas: the basal lateral amygdala (BLA) and nucleus accumbens (NAc). Our results demonstrate distinct activation patterns in the mPFC to BLA and mPFC to NAc pathways in response to social stimuli, indicating a mechanism for discriminating emotions: increased mPFC to BLA activity signals anxiety, while heightened mPFC to NAc responses are linked to exploration. Additionally, chronic emotional states amplify activity in these pathways, positivity enhances mPFC to NAc, while negativity boosts mPFC to BLA. This study sheds light on the nuanced neural circuitry involved in emotion regulation, revealing the pivotal roles of mPFC projections in emotional processing. Identifying these specific circuits engaged by varied emotional states advances our understanding of emotional regulation's biological underpinnings and highlights potential targets for addressing emotional dysregulation in psychiatric conditions.

Motor cortex perineuronal net modulation improves motor function in a Parkinson's disease mouse model
The 6-OHDA mouse model recapitulates midbrain dopaminergic cell loss and associated motor deficits akin to those observed in Parkinson's disease. Emerging evidence suggests that modulating interneurons in the primary motor cortex could offer a means to mitigate symptoms. In the cortex, perineuronal nets (PNNs), a specialized extracellular matrix structure generally present around fast-spiking parvalbumin interneurons, can modulate neural activity and circuit plasticity. We found that removing PNNs through unilateral or bilateral ChABC injection in the motor cortex temporarily altered motor behavior. Surprisingly, bilateral reduced motor cortex PNNs are observed two weeks after unilateral 6-OHDA midbrain lesions, whereas five weeks after lesion, PNNs return to control levels. Subsequent bilateral ChABC injections significantly improved motor function in 6-OHDA animals only when associated with motor stimulation involving enriched housing and daily motor training. Thus, PNN modulation in the motor cortex of a Parkinson's disease model enables local circuits to adapt to the loss of dopaminergic inputs, resulting in improved motor behavior.

Striatal cholinergic interneuron pause response requires Kv1 channels, is absent in dyskinetic mice, and is restored by dopamine D5 receptor inverse agonism
Striatal cholinergic interneurons (SCIN) exhibit pause responses conveying information about rewarding events, but the mechanisms underlying them remain elusive. Thalamic inputs induce a pause mediated by intrinsic mechanisms and regulated by dopamine D2 receptors, though the underlying membrane currents are unknown. Moreover, the role of D5 receptors (D5R) has not been addressed so far. We show that glutamate released by thalamic inputs in the dorsolateral striatum induces a burst in SCIN, followed by the activation of a Kv1-dependent delayed rectifier current responsible for the pause. Endogenous dopamine promotes the pause through D2R stimulation, while pharmacological stimulation of D5R suppresses it. Remarkably, the pause response is absent in parkinsonian mice rendered dyskinetic by chronic L-DOPA treatment but can be reinstated acutely by the inverse D5R agonist clozapine. Blocking the Kv1 current eliminates the pause reinstated by the D5R inverse agonist. In conclusion, the pause response is mediated by delayed rectifier Kv1 channels, which are tonically blocked in dyskinetic mice by a mechanism depending on D5R ligand-independent activity. Targeting these alterations may have therapeutic value in Parkinson's disease.

Role of the nucleus accumbens in signaled avoidance actions
Animals, humans included, navigate their environments guided by sensory cues, responding adaptively to potential dangers and rewards. Avoidance behaviors serve as adaptive strategies in the face of signaled threats, but the neural mechanisms orchestrating these behaviors remain elusive. Current circuit models of avoidance behaviors indicate that the nucleus accumbens (NAc) in the ventral striatum plays a key role in signaled avoidance behaviors, but the nature of this engagement is unclear. Evolving perspectives propose the NAc as a pivotal hub for action selection, integrating cognitive and affective information to heighten the efficiency of both appetitive and aversive motivated behaviors. To unravel the engagement of the NAc during active and passive avoidance, we used calcium imaging fiber photometry and single-unit recordings to examine NAc GABAergic neuron activity in freely moving mice performing avoidance behaviors. We then probed the functional significance of NAc neurons using optogenetics, and genetically targeted or electrolytic lesions. We found that NAc neurons code contraversive orienting movements and avoidance actions. Intriguingly, specific optogenetic patterns intended to excite NAc GABAergic neurons resulted in local somatic inhibition through GABAergic synaptic collaterals. Nevertheless, these patterns directly excited NAc GABAergic output axons, which in turn inhibited their targets, disrupting active avoidance behavior. Thus, this disruption stemmed from abnormal alterations in the activity of downstream midbrain areas crucial for the behavior. In contrast, direct optogenetic inhibition or lesions of NAc neurons did not impair active or passive avoidance behaviors, challenging the notion of their purported pivotal role in adaptive avoidance. The findings emphasize that NAc is not required for avoidance behaviors, but disruptions in NAc output during pathological states can impair these behaviors.

CRISPRi-based screen of Autism Spectrum Disorder risk genes in microglia uncovers roles of ADNP in microglia endocytosis and uptake of synaptic material
Autism Spectrum Disorders (ASD) are a set of neurodevelopmental disorders with complex biology. The identification of ASD risk genes from exome-wide association studies and de novo variation analyses has enabled mechanistic investigations into how ASD-risk genes alter development. Most functional genomics studies have focused on the role of these genes in neurons and progenitor cells. However, roles for ASD risk genes in other cell types are largely uncharacterized. There is evidence from postmortem tissue that microglia, the resident immune cells of the brain, appear activated in ASD. Here, we systematically assess the impact of ASD-risk gene knock-down on microglial uptake of synaptic material. We developed both an iPSC-derived microglia-neuron coculture system and high-throughput flow cytometry readout for synaptic uptake to enable CRISPRi-based screening. Our screen identified ADNP, one of the high-confidence ASD risk genes, amongst others as a modifier of microglial synaptic uptake. Transcriptomic, proteomic, and functional analyses revealed that ADNP plays a role in endocytosis, cell surface remodeling, and motility in microglia. Through this focused investigation into the role of ADNP in microglia, we also found preliminary evidence for WNT signaling coordinating microglial uptake of synaptic material.

Neuronal segmentation in cephalopod arms
The prehensile arms of the cephalopod are among these animals most remarkable features, but the neural circuitry governing arm and sucker movements remains largely unknown. We studied the neuronal organization of the adult axial nerve cord (ANC) of Octopus bimaculoides with molecular and cellular methods. The ANCs, which lie in the center of every arm, are the largest neuronal structures in the octopus, containing four times as many neurons as found in the central brain. In transverse cross section, the cell body layer (CBL) of the ANC wraps around its neuropil (NP) with little apparent segregation of sensory and motor neurons or nerve exits. Strikingly, when studied in longitudinal sections, the ANC is segmented. ANC neuronal cell bodies form columns separated by septa, with 15 segments overlying each pair of suckers. The segments underlie a modular organization to the ANC neuropil: neuronal cell bodies within each segment send the bulk of their processes directly into the adjoining neuropil, with some reaching the contralateral side. In addition, some nerve processes branch upon entering the NP, forming short-range projections to neighboring segments and mid-range projections to the ANC segments of adjoining suckers. The septa between the segments are employed as ANC nerve exits and as channels for ANC vasculature. Cellular analysis establishes that adjoining septa issue nerves with distinct fiber trajectories, which across two segments (or three septa) fully innervate the arm musculature. Sucker nerves also use the septa, setting up a nerve fiber ''suckerotopy'' in the sucker-side of the ANC. Comparative anatomy suggests a strong link between segmentation and flexible sucker-laden arms. In the squid Doryteuthis pealeii, the arms and the sucker-rich club of the tentacles have segments, but the sucker-poor stalk of the tentacles does not. The neural modules described here provide a new template for understanding the motor control of octopus soft tissues. In addition, this finding represents the first demonstration of nervous system segmentation in a mollusc.

Clearing-enabled light sheet microscopy as a novel method for three-dimensional mapping of the sensory innervation of the mouse knee
A major barrier that hampers our understanding of the precise anatomic distribution of pain sensing nerves in and around the joint is the limited view obtained from traditional two dimensional (D) histological approaches. Therefore, our objective was to develop a workflow that allows examination of the innervation of the intact mouse knee joint in 3D by employing clearing-enabled light sheet microscopy. We first surveyed existing clearing protocols (SUMIC, PEGASOS, and DISCO) to determine their ability to clear the whole mouse knee joint, and discovered that a DISCO protocol provided the most optimal transparency for light sheet microscopy imaging. We then modified the DISCO protocol to enhance binding and penetration of antibodies used for labeling nerves. Using the pan-neuronal PGP9.5 antibody, our protocol allowed 3D visualization of innervation in and around the mouse knee joint. We then implemented the workflow in mice intra-articularly injected with nerve growth factor (NGF) to determine whether changes in the nerve density can be observed. Both 3D and 2D analytical approaches of the light sheet microscopy images demonstrated quantifiable changes in midjoint nerve density following 4 weeks of NGF injection in the medial but not in the lateral joint compartment. We provide, for the first time, a comprehensive workflow that allows detailed and quantifiable examination of mouse knee joint innervation in 3D.

AKT2 modulates astrocytic nicotine responses in vivo.
A better understanding of nicotine neurobiology is needed to reduce or prevent chronic addiction, ameliorate the detrimental effects of nicotine withdrawal, and increase successful cessation of use. Nicotine binds and activates two astrocyte-expressed nicotinic acetylcholine receptors (nAChRs), 4{beta}2 and 7. We recently found that Protein kinase B-{beta} (Pkb-{beta} or Akt2) expression is restricted to astrocytes in mice and humans. To determine if AKT2 plays a role in astrocytic nicotinic responses, we generated astrocyte-specific Akt2 conditional knockout (cKO) and full Akt2 KO mice for in vivo and in vitro experiments. For in vivo studies, we examined mice exposed to chronic nicotine for two weeks in drinking water (200 g/mL) and following acute nicotine challenge (0.09, 0.2 mg/kg) after 24 hrs. Our in vitro studies used cultured mouse astrocytes to measure nicotine-dependent astrocytic responses. We validated our approaches using lipopolysaccharide (LPS) exposure inducing astrogliosis. Sholl analysis was used to measure glial fibrillary acidic protein responses in astrocytes. Our data show that wild-type (WT) mice exhibit increased astrocyte morphological complexity during acute nicotine exposure, with decreasing complexity during chronic nicotine use, whereas Akt2 cKO mice showed increased astrocyte morphology complexity. In culture, we found that 100M nicotine was sufficient for morphological changes and blocking 7 or 4{beta}2 nAChRs prevented observed morphologic changes. Finally, we performed conditioned place preference (CPP) in Akt2 cKO mice and found that astrocytic AKT2 deficiency reduced nicotine preference compared to controls. These findings show the importance of nAChRs and Akt2 signaling in the astrocytic response to nicotine.

Computer vision guided open-source active commutator for neural imaging in freely behaving animals
Recently developed miniaturized neural recording devices that can monitor and perturb neural activity in freely behaving animals have significantly expanded our knowledge neural underpinning of complex behaviors. Most miniaturized neural interfaces require a wired connection for external power and data acquisition systems. The wires are required to be commutated through a slip ring to accommodate for twisting of the wire or tether and alleviate torsional stresses. The increased trend towards long term continuous neural recordings have spurred efforts to realize active commutators that can sense the torsional stress and actively rotation the slip ring to alleviate torsional stresses. Current solutions however require addition of sensing modules. Here we report on an active translating commutator that uses computer vision (CV) algorithms on behavioral imaging videos captured during the experiment to track the animal's position and heading direction in real-time and uses this information to control the translation and rotation of a slipring commutator to accommodate for accumulated mouse heading orientation changes and position. The CV guided active commutator has been extensively tested in three separate behavioral contexts and we show reliable cortex-wide imaging in a mouse in an open-field with a miniaturized widefield cortical imaging device. Active commutation resulted in no changes to measured neurophysiological signals. The active commutator is fully open source, can be assembled using readily available off-the-shelf components, and is compatible with a wide variety of miniaturized neurophotonic and neurophysiology devices.

Brain-state modeling using electroencephalography: Application to adaptive closed-loop neuromodulation for epilepsy
The progress of developing an effective closed-loop neuromodulation system for many neurological pathologies is hindered by the difficulties in accurately capturing a useful representation of a brain's instantaneous functional state. Existing approaches rely on expert labeling of electroencephalography data to develop biomarkers of neurophysiological pathology. These techniques do not capture the highly complex functional states of the brain that are presumed to exist between labeled states or allow for the likely possibility of variation among identically labeled states. Thus, we propose BrainState, a self-supervised technique to model an arbitrarily complex instantaneous functional state of a brain using neural multivariate timeseries data. Application of BrainState to intracranial electroencephalography data from patients with epilepsy was able to capture diverse pre-seizure states and quantify nuanced effects of neuromodulation. We anticipate that BrainState will enable the development of sophisticated closed-loop neuromodulation systems for a diverse array of neurological pathologies.

Alzheimer's disease-associated protective variant Plcg2-P522R modulates peripheral macrophage function in a sex-dimorphic manner and confers functional advantage in female mice
Genome-wide association studies have identified a protective mutation in the phospholipase C gamma 2 (PLCG2) gene which confers protection against Alzheimer's disease (AD)-associated cognitive decline. Therefore, PLCG2, which is primarily expressed in immune cells, has become a target of interest for potential therapeutic intervention. The protective allele, known as P522R, has been shown to be hyper-morphic in microglia, increasing phagocytosis of amyloid-beta (A{beta}), and increasing the release of inflammatory cytokines. However, the effect of this protective mutation on peripheral tissue-resident macrophages, and the extent to which sex modifies this effect, has yet to be assessed. Herein, we show that peripheral macrophages from wild-type (WT) female and male mice harbor intrinsic differences, with macrophages from females exhibiting less phagocytosis and lysosomal protease activity, as well as a more pro-inflammatory phenotype upon stimulation compared to those from male mice. Furthermore, we demonstrate that the P522R mutation does indeed alter peripheral macrophage function in a sex-dependent manner, with more prominent effects seen in females, including pushing macrophages from females toward an M2 protective phenotype that more closely resembles macrophages from males. These results suggest that the P522R mutation may be partially conferring protection against protein aggregation via activation of peripheral immune cell function and underscore the importance of considering sex as a biological variable when assessing the viability of potential immune system-targeted therapies.

D-Serine inhibits non-ionotropic NMDA receptor signaling
NMDA-type glutamate receptors (NMDARs) are widely recognized as master regulators of synaptic plasticity, most notably for driving long-term changes in synapse size and strength that support learning. NMDARs are unique among neurotransmitter receptors in that they require binding of both neurotransmitter (glutamate) and co-agonist (e.g. D-serine) to open the receptor channel, which leads to the influx of calcium ions that drive synaptic plasticity. Over the past decade, evidence has accumulated that NMDARs also support synaptic plasticity via ion flux-independent (non-ionotropic) signaling upon the binding of glutamate in the absence of co-agonist, although conflicting results have led to significant controversy. Here, we hypothesized that a major source of contradictory results can be attributed to variable occupancy of the co-agonist binding site under different experimental conditions. To test this hypothesis, we manipulated co-agonist availability in acute hippocampal slices from mice of both sexes. We found that enzymatic scavenging of endogenous co-agonists enhanced the magnitude of LTD induced by non-ionotropic NMDAR signaling in the presence of the NMDAR pore blocker, MK801. Conversely, a saturating concentration of D-serine completely inhibited both LTD and spine shrinkage induced by glutamate binding in the presence of MK801. Using a FRET-based assay in cultured neurons, we further found that D-serine completely blocked NMDA-induced conformational movements of the GluN1 cytoplasmic domains in the presence of MK801. Our results support a model in which D-serine inhibits ion flux-independent NMDAR signaling and plasticity, and thus D-serine availability could serve to modulate NMDAR signaling even when the NMDAR is blocked by magnesium.

Functional efficacy of the MAO-B inhibitor safinamide in murine substantia nigra pars compacta dopaminergic neurons in vitro: a comparative study with tranylcypromine
Safinamide (SAF) is currently used to treat Parkinson's disease (PD) symptoms based on its theoretical ability to potentiate the dopamine (DA) signal, blocking monoamine oxidase (MAO) B. The present work aims to highlight the functional relevance of SAF as an enhancer of the DA signal, by evaluating its ability to prolong recovery from DA-mediated firing inhibition of DAergic neurons of the substantia nigra pars compacta (SNpc), compared to another MAO antagonist, tranylcypromine (TCP). Using multielectrode array (MEA) and single electrode extracellular recordings of spontaneous spikes from presumed SNpc DAergic cells in vitro, we show that SAF (30 uM) mildly prolongs the DA-mediated firing inhibition, as opposed to the profound effect of TCP (10 uM). In patch-clamp recordings, we found that SAF (30 uM) significantly reduced the number of spikes evoked by depolarizing currents in SNpc DAergic neurons, in a sulpiride (1 uM) independent manner. According to our results, SAF marginally potentiates the DA signal in SNpc DAergic neurons, while exerting an inhibitory effect on the postsynaptic excitability acting on membrane conductances. Thus, we propose that the therapeutic effects of SAF in PD patients partially depends on MAO inhibition, while other MAO-independent sites of action could be more relevant.

A hemispheric dome setup for naturalistic visual stimulation in head-fixed mice
The visual system of any animal species is adapted to its ecological niche. Thus, investigating visual function and behavior using naturalistic stimuli holds significant potential. In mice, these adaptations include a field of view of ~280{degrees} and cone opsins sensitive to UV and green wavelengths. Such adaptations, however, cannot be probed with standard consumer displays. To present naturalistic visual stimuli to mice, we built a hemispheric dome setup, enabling the controlled projection of wide-field movies with UV-green spectral content. For our UV-green projection, we used a customized light engine with external high-power LEDs. We mitigated spatial distortions introduced by the projection through a geometry-independent calibration procedure. Additionally, we adapted a head-mounted eye tracking system to capture behavioral responses of head-fixed mice viewing these stimuli. We validated our setup by quantifying the pupillary light reflex to uniform stimuli and the optokinetic reflex to drifting gratings. Finally, in experiments with naturalistic movies, we investigated whether mice showed differential saccades and eye positions based on visual input. Comparing naturalistic movies to a uniform screen control condition, we observed that although head-fixed mice did not make targeted saccades during movies, their overall eye position consistently shifted towards more frontal regions of visual space. This indicates that mice adjust their eye position in a stimulus-dependent way, potentially to optimize visual processing of information ahead in the visual field. Together, our results highlight the utility of our setup for in vivo studies of the mouse visual system with more naturalistic visual stimulation.

No Electrophysiological Evidence for Semantic Processing During Inattentional Blindness
A long-standing question concerns whether sensory input can reach semantic stages of processing in the absence of attention and awareness. Here, we examine whether the N400, an event related potential associated with semantic processing, can occur under conditions of inattentional blindness. By employing a novel three-phase inattentional blindness paradigm designed to maximise the opportunity for detecting an N400, we found no evidence for it when participants were inattentionally blind to the eliciting stimuli (related and unrelated word pairs). In contrast, when minimal attention was allocated to the same task-irrelevant word pairs, participants became aware of them, and a small N400 became evident. Finally, when the same stimuli were fully attended and relevant to the task, a robust N400 was observed. In addition to univariate ERP measures, multivariate decoding analyses were unable to classify related versus unrelated word pairs when observers were inattentionally blind to the words, with decoding reaching above-chance levels only when the words were (at least minimally) attended. Our results also replicated several previous studies by finding a visual awareness negativity (VAN) that distinguished task-irrelevant stimuli that were perceived compared with those that were not perceived, and a P3b (or late positivity) that was evident only when the stimuli were perceived and task relevant. Together, our findings suggest that semantic processing might require at least a minimal amount of attention.

Dynamic functional connectivity is modulated by the amount of p-Tau231 in blood in cognitively intact participants
INTRODUCTION Electrophysiology and plasma biomarkers are early and non-invasive candidates for Alzheimer's disease detection. The purpose of this paper is to evaluate changes in dynamic functional connectivity measured with magnetoencephalography, associated with the plasma pathology marker p-tau231 in unimpaired adults. METHODS 73 individuals were included. Static and dynamic functional connectivity were calculated using leakage corrected amplitude envelope correlation. Each source's strength entropy across trials was calculated. A data-driven statistical analysis was performed to find the association between functional connectivity and plasma p-tau231 levels. Regression models were used to assess the influence of other variables over the clusters' connectivity. RESULTS Frontotemporal dynamic connectivity positively associated with p-tau231 levels. Linear regression models identified pathological, functional and structural factors that influence dynamic functional connectivity. DISCUSSION These results expand previous literature on dynamic functional connectivity in healthy individuals at risk of AD, highlighting its usefulness as an early, non-invasive and more sensitive biomarker.

Peripheral Neuropathy in the Adreno-myelo-neuropathy Mouse Model
The Abcd1 knockout mouse mimics human adreno-myelo-neuropathy (AMN), thus contributes to a better understanding of disease mechanisms, which yet remain poorly identified. Only limited information is available about peripheral neuropathy (PN), although a notable component of AMN pathology besides myelopathy. To enrich our knowledge of PN, the current study reports the clinical, electromyographic and morphological aspects of peripheral neuropathy. We found that despite obvious electron microscopy anomalies in sciatic nerve axons, nerve conduction was nearly normal and did not seem to contribute significantly to the impaired motor performances of the Abcd1-/- mouse.

Emergence of a dynamical state of coherent bursting with power-law distributed avalanches from collective stochastic dynamics of adaptive neurons
Spontaneous brain activity in the absence of external stimuli is not random but contains complex dynamical structures such as neuronal avalanches with power-law duration and size distributions. These experimental observations have been interpreted as supporting evidence for the hypothesis that the brain is operating at criticality and attracted much attention. Here, we show that an entire state of coherent bursting, with power-law distributed avalanches and features as observed in experiments, emerges in networks of adaptive neurons with stochastic input when excitation is sufficiently strong and balanced by adaptation. We demonstrate that these power-law distributed avalanches are direct consequences of stochasticity and the oscillatory population firing rate arising from coherent bursting, which in turn is the result of the balance between excitation and adaptation, and criticality does not play a role.

A glial circadian gene expression atlas reveals cell type and disease-specific reprogramming in response to amyloid pathology or aging.
While circadian rhythm disruption may promote neurodegenerative disease, how aging and neurodegenerative pathology impact circadian gene expression patterns in different brain cell types is unknown. Here, we used translating ribosome affinity purification methods to define the circadian translatomes of astrocytes, microglia, and bulk cerebral cortex, in healthy mouse brain and in the settings of amyloid-beta plaque pathology or aging. Our data reveal that glial circadian translatomes are highly cell type-specific and exhibit profound, context-dependent reprogramming of rhythmic transcripts in response to amyloid pathology or aging. Transcripts involved in glial activation, immunometabolism, and proteostasis, as well as nearly half of all Alzheimer Disease (AD)-associated risk genes, displayed circadian oscillations, many of which were altered by pathology. Amyloid-related differential gene expression was also dependent on time of day. Thus, circadian rhythms in gene expression are cell- and context dependent and provide important insights into glial gene regulation in health, AD, and aging.

The within-subject stability of cortical thickness, surface area, and brain volumes across one year
With the feature of noninvasively monitoring the human brain, magnetic resonance imaging (MRI) has become a ubiquitous means to understand how the brain works. Specifically, T1-weighted (T1w) imaging is widely used to examine the brain structure where the cortical thickness, surface area, and brain volumes have been investigated. These T1w-derived phenotypes undergo radical changes during childhood and adolescence, while remaining relatively stable during adulthood. However, stability over a short time (e.g. one year) during adulthood is still unknown. Additionally, how environmental factors such as time-of-day and different daylight lengths could impact the structural brain is also elusive. The main purpose of this study, therefore, was to assess the stability of T1w-derived phenotypes, i.e., cortical thickness, surface area, and brain volumes including subcortical volumes, and to explore the time-of-day and daylight length effects. Accordingly, three subjects in their late 20s, and early 30s and 40s were scanned repeatedly on the same scanner over one year from which a deep brain imaging dataset was constructed with 38, 40, and 25 sessions for subjects 1, 2, and 3, respectively. The T1w-derived phenotypes demonstrated percentage changes within 5% and CVs (coefficients of variance) within 2% for the majority of brain regions. However, several brain regions did show larger variations with percentage changes around 10% and CVs around 5%, such as the temporal pole, the frontal pole, and the entorhinal cortex. More importantly, there were no significant effects of time-of-day and daylight length. Moreover, cortical thickness change was strongly and positively correlated with that of volume while being negatively correlated with that of surface area, illustrating their distinct roles in brain anatomy. Additionally, it was found that apparent head motion causes cortical thickness and volume to be underestimated and surface area to be overestimated. These results indicate that T1w-derived phenotypes are reasonably stable regardless of time-of-day or daylight length, but that head motion should be taken into consideration.

Decomposed Linear Dynamical Systems (dLDS) modelsreveal context-dependent dynamic connectivity in C. elegans
Despite innumerable efforts to characterize C. elegans neural activity and behavior, the roles of each individual neuron and the compositional mechanisms of all their interactions are still not completely known. In particular, there is evidence that C. elegans neurons perform changing roles over time, in different behavioral contexts, etc.; however, existing stationary anatomical and functional connectivity can average across time and obfuscate the nonstationary nature of the neural dynamics. We contribute to these efforts by leveraging recent advances in decomposed linear dynamical systems (dLDS) models. dLDS models neural dynamics in a latent space with a set of linear operators that can be recombined and reused over time, enabling the discovery of multiple parallel neural processes on different timescales. We leverage the ability to identify reused patterns of dynamical neural interactions, which we call "dynamical connectivity," to 1) identify contextually dependent roles of neurons; 2) discover the underlying variability of neural representations even under discrete behaviors; 3) quantify differences between anatomical, functional, and dynamical connectivity; and 4) learn a single aligned latent space underlying multiple individual worms' activity. These results highlight the importance of defining a neuron's functions not solely by its internal activity or place in a time-averaged network, but by its evolving interactions across context-dependent circuits.

A melancholy machine: simulated synapse loss induces depression-like behaviors in deep reinforcement learning
Deep Reinforcement Learning is a branch of artificial intelligence that uses artificial neural networks to model reward-based learning as it occurs in biological agents. Here we modify a Deep Reinforcement Learning approach by imposing a suppressive effect on the connections between neurons in the artificial network - simulating the effect of dendritic spine loss as observed in major depressive disorder (MDD). Surprisingly, this simulated spine loss is sufficient to induce a variety of MDD-like behaviors in the artificially intelligent agent, including anhedonia, increased temporal discounting, avoidance, and an altered exploration/exploitation balance. Furthermore, simulating alternative and longstanding reward-processing-centric conceptions of MDD (dysfunction of the dopamine system, altered reward discounting, context-dependent learning rates, increased exploration) does not produce the same range of MDD-like behaviors. These results support a conceptual model of MDD as a reduction of brain connectivity (and thus information-processing capacity) rather than an imbalance in monoamines - though the computational model suggests a possible explanation for the dysfunction of dopamine systems in MDD. Reversing the spine-loss effect in our computational MDD model can lead to rescue of rewarding behavior under some conditions. This supports the search for treatments that increase plasticity and synaptogenesis, and the model suggests some implications for their effective administration.

Neural correlates of device-based sleep characteristics in adolescents
Understanding the brain mechanisms underlying objective sleep patterns in adolescents and their implications for psychophysiological development is a complex challenge. Here, we applied sparse canonical correlation (sCCA) analysis on 3300 adolescents from Adolescent Brain Cognitive Development (ABCD) study, integrating extensive device-based sleep characteristics and multimodal imaging data. We revealed two sleep-brain dimensions: one characterized by later being asleep and shorter duration, linked to decreased subcortical-cortical network functional connectivities; the other showed higher heart rate and shorter light sleep duration, associated with lower brain volumes and decreased functional connectivities. Hierarchical clustering based on brain dimension associated with sleep characteristics revealed three biotypes of adolescents, marked by unique sleep profiles: biotype 1 exhibited delayed and shorter sleep, coupled with higher heart rate during sleep; biotype 3 with earlier and longer sleep, accompanied by lower heart rate; and biotype 2 with intermediate pattern. This biotypic differences also extended to cognition, academic attainment, brain structure and function in a gradient order. Longitudinal analysis demonstrated consistent biotypic differences from ages 9 to14, highlighting enduring cognitive and academic advantages in biotype3. The linked sleep-brain dimensions and the associated biotypes were well replicated in a longitudinal sample of 1271 individuals. Collectively, our novel findings delineate a linkage between objective sleep characteristics and developing brain in adolescents, underscoring their significance in cognitive development and academic attainment, which could serve as references for individuals with sleep difficulties and offer insights for optimizing sleep routines to enhance better cognitive development and school achievement.

Serotonin-2B receptor (5-HT2BR) expression and binding in the brain of ageing APPswe/PS1de9 transgenic mice and in human Alzheimer's disease brain tissue
Although evidence of dysregulation in central serotonergic signalling is widespread in Alzheimer's disease (AD), relatively little is known about the specific involvement of the serotonin-2B receptor (5-HT2BR) subtype. Here, we assessed 5-HT2BR expression and binding in brain tissue from APPswe/PS1dE9 transgenic (TG) mice and AD patients. 5-HT2BR mRNA was measured by RT-qPCR in 3- to >18-month-old TG and wild-type (WT) littermate mice (n=3-8), and in middle frontal gyrus samples from female, AD and control subjects (n=7-10). The density of 5-HT2BRs was measured by autoradiography using 1 nM [3H]RS127445 and 1 M LY266097. In both mouse and human samples, 5-HT2BR mRNA was detectable after 33 amplification cycles. mRNA levels in WT mice, not TG mice, increased with age, and were higher in AD patients compared to control subjects. [3H]RS127445 binding was low in the mouse brain, detected after 3 months of age. 5-HT2BR density was overall lower in the hippocampus of TG compared to WT mice. Specific binding was too low to be reliably quantified in the human samples. These data provide evidence of a different 5-HT2BR expression and binding in the APPswe/PS1dE9 TG model of AD and AD patients. Studies investigating the functional involvement of the 5-HT2BR in AD are warranted.

Aging disrupts the coordination between mRNA and protein expression in mouse and human midbrain
Age-related dopamine (DA) neuron loss is a primary feature of Parkinsons disease. However, it remains unclear whether similar biological processes occur during healthy aging, albeit to a lesser degree. We therefore determined whether midbrain DA neurons degenerate during aging in mice and humans. In mice, we identified no changes in midbrain neuron numbers throughout aging. Despite this, we found age-related decreases in midbrain mRNA expression of tyrosine hydroxylase (Th), the rate limiting enzyme of DA synthesis. Among midbrain glutamatergic cells, we similarly identified age-related declines in vesicular glutamate transporter 2 (Vglut2) mRNA expression. In co-transmitting Th+/Vglut2+ neurons, Th and Vglut2 transcripts decreased with aging. Importantly, striatal Th and Vglut2 protein expression remained unchanged. In translating our findings to humans, we found no midbrain neurodegeneration during aging and identified age-related decreases in TH and VGLUT2 mRNA expression similar to mouse. Unlike mice, we discovered diminished density of striatal TH+ dopaminergic terminals in aged human subjects. However, TH and VGLUT2 protein expression were unchanged in the remaining striatal boutons. Finally, in contrast to Th and Vglut2 mRNA, expression of most ribosomal genes in Th+ neurons was either maintained or even upregulated during aging. This suggests a homeostatic mechanism where age-related declines in transcriptional efficiency are overcome by ongoing ribosomal translation. Overall, we demonstrate species-conserved transcriptional effects of aging in midbrain dopaminergic and glutamatergic neurons that are not accompanied by marked cell death or lower striatal protein expression. This opens the door to novel therapeutic approaches to maintain neurotransmission and bolster neuronal resilience.

The Interplay of Prior Information and Motion Cues in Resolving Visual Ambiguity in Agent Perception
Agent perception is essential for social interaction, allowing individuals to interpret and respond to the actions of others within dynamic environments. In this study, we examined how prior knowledge and motion cues are integrated to influence the temporal dynamics of perceiving agents. In order to make realistic but ambiguous stimuli in motion and form characteristics, we used human, robot, and android agents. Using temporal representational similarity analysis (RSA) on EEG recordings, we analyzed the representation of agent identities under varying conditions: Still versus Moving stimuli and Prior versus Naive contexts. Our findings revealed that prior knowledge and motion cues interact to produce distinct temporal patterns of representation. In the naive condition, information about the agent persisted longer during still presentations than during moving ones, suggesting that the processing of agents depends on the availability of motion information and prior information. Moreover, motion information affects the temporal processing of agents when no prior information about agents is available. These results highlight the critical roles of both bottom-up sensory inputs and top-down expectations and their interactions in resolving the ambiguities inherent in agent perception.

Using N2pc variability to probe functionality: Linear mixed modelling of trial EEG and behaviour
This paper has two concurrent goals. On one hand, we hope it will serve as a simple primer in the use of linear mixed modelling (LMM) for inferential statistical analysis of multimodal data. We describe how LMM can be easily adopted for the identification of trial-wise relationships between disparate measures and provide a brief cookbook for assessing the suitability of LMM in your analyses. On the other hand, this paper is an empirical report, probing how trial-wise variance in the N2pc, and specifically its sub-component the NT, can be predicted by manual reaction time (RT) and stimuli parameters. Extant work has identified a link between N2pc and RT that has been interpreted as evidence of a direct and causative relationship. However, results have left open the less-interesting possibility that the measures covary as a function of motivation or arousal. Using LMM, we demonstrate that the relationship only emerges when the NT is elicited by targets, not distractors, suggesting a discrete and functional relationship. In other analyses, we find that the target-elicited NT is sensitive to variance in distractor identity even when the distractor cannot itself elicit consistently lateralized brain activity. The NT thus appears closely linked to attentional target processing, supporting the propagation of target-related information to response preparation and execution. At the same time, we find that this component is sensitive to distractor interference, which leaves open the possibility that NT reflects brain activity responsible for the suppression of irrelevant distractor information.

The Impact of Scene Context on Visual Object Recognition: Comparing Humans, Monkeys, and Computational Models
During natural vision, we rarely see objects in isolation but rather embedded in rich and complex contexts. Understanding how the brain recognizes objects in natural scenes by integrating contextual information remains a key challenge. To elucidate neural mechanisms compatible with human visual processing, we need an animal model that behaves similarly to humans, so that inferred neural mechanisms can provide hypotheses relevant to the human brain. Here we assessed whether rhesus macaques could model human context-driven object recognition by quantifying visual object identification abilities across variations in the amount, quality, and congruency of contextual cues. Behavioral metrics revealed strikingly similar context-dependent patterns between humans and monkeys. However, neural responses in the inferior temporal (IT) cortex of monkeys that were never explicitly trained to discriminate objects in context, as well as current artificial neural network models, could only partially explain this cross-species correspondence. The shared behavioral variance unexplained by context-naive neural data or computational models highlights fundamental knowledge gaps. Our findings demonstrate an intriguing alignment of human and monkey visual object processing that defies full explanation by either brain activity in a key visual region or state-of-the-art models.

Neuronal toxicity and recovery from early bortezomib-induced neuropathy: targeting the blood nerve barrier but not the dorsal root ganglion
The use of the first in class proteasome inhibitor Bortezomib (BTZ) is highly effective in the treatment of multiple myeloma. However, its long-term use is limited by the fact, that most treated patients develop dose limiting painful polyneuropathy. In some of the treated patients, pain resolves after variable timeframes, in others it persists, despite the discontinuation of treatment, with the underlying mechanisms poorly understood. One condition of neural toxicity is the ability to penetrate the blood nerve barrier. Here we present pathways involved in early bortezomib-induced polyneuropathy (BIPN) development and its resolution, in rats and in myeloma patients. One cycle of BTZ elicited transient mechanical hyperalgesia and cold allodynia in rats. Transcriptomic signature and network analysis revealed regulation of circadian, extracellular matrix, and immune genes within the nerve and modest changes in the dorsal root ganglia. Recovery processes resealed the small molecule leakiness of the perineurial barrier, reversed axonal swelling, and normalized small fiber density in the skin. Expression of the microtubule-associated cytoskeletal protein cortactin matched this process in the perineurium. Netrin-1 (Ntn1) as a known barrier sealer was also upregulated in pain resolution in nerve and skin. In patients with painful BIPN skin NTN1 was independent of axonal damage. In summary, our data demonstrate that early BTZ toxicity targets mainly the nerve and indicates that pain resolution could be supported by protective growth factors like Ntn1 for remodeling of the extracellular matrix and neuronal barriers.

Integrating Data Across Oscillatory Power Bands Predicts the Epileptogenic Zone: the Frequency Range Explorer Epileptogenic Zone (FREEZ) Identification Algorithm
Epilepsy affects over 70 million people globally. One-third of people with focal epilepsy have drug-resistant epilepsy. Identification and removal of the site of onset of seizures, termed the epileptogenic zone (EZ), is the most successful treatment to stop seizures in these people. Implanting electrodes into the brain with intracranial electroencephalography (iEEG) is the gold standard diagnostic test for identifying the EZ. But identification of the EZ with iEEG remains challenging in many cases. We developed a novel computational methodology that integrates mean power across delta, theta, alpha, beta, gamma, and high gamma frequencies over time to identify the EZ. A machine learning model was trained to predict electrodes within the EZ using publicly available data from 21 patients. In patients that were seizure free after surgery, electrodes within the EZ had significantly higher area under the curve (AUC) for mean power over time in the first 20 seconds after a seizure compared to electrodes outside the EZ in the alpha (p = 0.001), beta (p = 0.001), gamma (p <0.0001), and high gamma (p = 0.0003) ranges. Additionally, electrodes within the EZ in patients that became seizure-free after surgery had significantly higher AUC compared to electrodes marked within the EZ in patients who did not become seizure-free after surgery in the gamma (p = 0.0006) and high gamma (p <0.0001) power ranges. Leave-one-out patient cross validation of the machine learning model yielded a 95.7% positive predictive value and 80.6% specificity for identifying electrodes within the epileptogenic zone, and 90.5% accuracy for predicting seizure outcome based on a planned resection. We implemented this algorithm into the open-source software tool "Reproducible Analysis and Visualization of iEEG" (RAVE) to enable users to reproduce our results and implement this methodology with new datasets, creating a software module we title FREEZ. The software facilitates quantification of the spectral power changes during seizures, including displaying time-frequency spectrograms and projecting results across patient-specific 3D brain maps. Users can also adjust parameters for visualizing multiple frequency ranges from various time regions around seizure onsets in a web-browser-based interface.

IL1A enhances TNF-induced retinal ganglion cell death
Glaucoma is a neurodegenerative disease that leads to the death of retinal ganglion cells (RGCs). A growing body of literature suggests a role for neuroinflammation in RGC death after glaucoma-relevant insults. For instance, it was shown that deficiency of three proinflammatory cytokines, complement component 1, subcomponent q (C1q), interleukin 1 alpha (Il1a), and tumor necrosis factor (Tnf), resulted in near complete protection of RGCs after two glaucoma-relevant insults, optic nerve injury and ocular hypertension. While TNF and C1Q have been extensively investigated in glaucoma-relevant model systems, the role of IL1A in RGC is not as well defined. Thus, we investigated the direct neurotoxicity of IL1A on RGCs in vivo. Intravitreal injection of IL1A did not result in RGC death at either 14 days or 12 weeks after insult. Consistent with previous studies, TNF injection did not result in significant RGC loss at 14 days but did after 12 weeks. Interestingly, IL1A+TNF resulted in a relatively rapid RGC death, driving significant RGC loss two weeks after injection. JUN activation and SARM1 have been implicated in RGC death in glaucoma and after cytokine insult. Using mice deficient in JUN or SARM1, we show RGC loss after IL1A+TNF insult is JUN-independent and SARM1-dependent. Furthermore, RNA-seq analysis showed that RGC death by SARM1 deficiency does not stop the neuroinflammatory response to IL1A+TNF. These findings indicate that IL1A can potentiate TNF-induced RGC death after combined insult is likely driven by a SARM1-dependent RGC intrinsic signaling pathway.

Snake venom-inspired novel peptides protect Caenorhabditis elegans against paraquat induced Parkinson's pathology
The in vivo protective mechanisms of two low molecular mass novel custom peptides (CPs) against paraquat (PT) induced neurodegenerative dysfunction in the Caenorhabditis elegans model were deciphered. CPs prevent the PT binding to the nerve ring adjacent to the pharynx in C elegans (N2 strain) by stable and high-affinity binding to the tyrosine protein kinase receptor CAM 1, resulting in significant inhibition of PT induced toxicity by reducing enhanced reactive oxygen species production, mitochondrial membrane depolarization, and chemosensory dysfunction. The CPs inhibited PT induced dopaminergic (DAergic) neuron degeneration and alpha synuclein aggregation, the hallmarks of Parkinsons Disease, in transgenic BZ555 and NL5901 strains of C elegans. The transcriptomic, functional proteomics, and quantitative reverse transcription polymerase chain reaction (qRT PCR) analyses show that CPs prevented the increased expression of the genes involved in the skn 1 downstream pathway, thereby restoring PT mediated oxidative stress, apoptosis, and neuronal damage in C elegans. The CPs ability to repair PT induced damage was demonstrated by a network of gene expression profiles illustrating the molecular relationships between the regulatory proteins. Further, CPs did not show toxicity or induce inflammatory mediators in the mouse model.

Psilocybin reduces heroin seeking behavior and modulates inflammatory gene expression in the nucleus accumbens and prefrontal cortex of male rats
Preclinical and human studies indicate psilocybin may reduce perseverant maladaptive behaviors, including nicotine and alcohol seeking. Such studies in the opioid field are lacking, though opioids are involved in more >50% of overdose deaths. Psilocybin is an agonist at the serotonin 2A receptor (5-HT2AR), a well-documented target for modulation of drug seeking, and evidence suggests 5-HT2AR agonists may dampen motivation for opioids. We sought to investigate the therapeutic efficacy of psilocybin in mediating cessation of opioid use and maintenance of long-lasting abstinence from opioid seeking behavior in a rat model of heroin self-administration (SA). Psilocybin or 5-HT2AR antagonists ketanserin and volinanserin were administered systemically to rats prior to SA of 0.075 mg/kg/infusion of heroin, or relapse following forced abstinence. Psilocybin did not alter heroin taking, but a single exposure to 3.0 mg/kg psilocybin 4-24 hours prior to a relapse test blunted cue-induced heroin seeking. Conversely, 5-HT2AR antagonists exacerbated heroin relapse. To begin to elucidate mechanisms of psilocybin, drug-naive rats received psilocybin and/or ketanserin, and tissue was collected from the prefrontal cortex (PFC), a region critical for drug seeking and responsive to psilocybin, 24 hours later for RNA-sequencing. 3.0 mg/kg psilocybin regulated ~2-fold more genes in the PFC than 1.0 mg/kg, including genes involved in the cytoskeleton and cytokine signaling. Ketanserin blocked >90% of psilocybin-regulated genes, including the IL-17a cytokine receptor, Il17ra. Psychedelic compounds have reported anti-inflammatory properties, and therefore we performed a gene expression array to measure chemokine/cytokine molecules in the PFC of animals that displayed psilocybin-mediated inhibition of heroin seeking. Psilocybin regulated 4 genes, including Il17a, and a subset of genes correlated with relapse behavior. Selective inhibition of PFC IL-17a was sufficient to reduce heroin relapse. We conclude that psilocybin reduces heroin relapse and highlight IL-17a signaling as a potential downstream pathway of psilocybin that also reduces heroin seeking.

Modular Arrangement of Synaptic and Intrinsic Homeostatic Plasticity within Visual Cortical Circuits
Neocortical circuits use synaptic and intrinsic forms of homeostatic plasticity to stabilize key features of network activity, but whether these different homeostatic mechanisms act redundantly, or can be independently recruited to stabilize different network features, is unknown. Here we used pharmacological and genetic perturbations both in vitro and in vivo to determine whether synaptic scaling and intrinsic homeostatic plasticity (IHP) are arranged and recruited in a hierarchical or modular manner within L2/3 pyramidal neurons in rodent V1. Surprisingly, although the expression of synaptic scaling and IHP was dependent on overlapping trafficking pathways, they could be independently recruited by manipulating spiking activity or NMDAR signaling, respectively. Further, we found that changes in visual experience that affect NMDAR activation but not mean firing selectively trigger IHP, without recruiting synaptic scaling. These findings support a modular model in which synaptic and intrinsic homeostatic plasticity respond to and stabilize distinct aspects of network activity.

Lysophosphatidic acid receptor 1 influences disease severity in a mouse model of multiple sclerosis
Multiple sclerosis (MS), a chronic inflammatory disease affecting the central nervous system (CNS), is characterized by demyelination and axonal degeneration. Current treatments, which focus mainly on reducing lymphocyte infiltration into the CNS, are insufficient due to serious side effects and limited effectiveness; thus, identifying drugs with new mechanisms of action is crucial. Lysophosphatidic acid (LPA), a bioactive lipid produced by the enzyme autotaxin, may play a role in MS pathogenesis. Specifically, the LPA1 subtype of LPA receptors is linked to release of inflammatory cytokines in the CNS, and to demyelination in the peripheral nervous system. Our study investigated the role of LPA1 in a mouse model of MS. Knocking out the LPA1 gene in mice with experimental autoimmune encephalomyelitis improved clinical outcomes and reduced demyelination. Additionally, the absence of LPA1 reduced activation of Iba1-positive cells. Treatment with AM095, an LPA1 antagonist, tended to improve clinical outcomes and reduce levels of inflammatory mediators. These findings indicate that activation of LPA1 contributes to MS pathogenesis by promoting microglial activation and infiltration of peripheral immune cells.

L-Arginine and asymmetric dimethylarginine (ADMA) transport across the mouse blood-brain and blood-CSF barriers: evidence of saturable transport at both interfaces and CNS to blood efflux.
L-Arginine is the physiological substrate for the nitric oxide synthase (NOS) family, which synthesises nitric oxide (NO) in endothelial and neuronal cells. NO synthesis can be inhibited by endogenous asymmetric dimethylarginine (ADMA). NO has explicit roles in cellular signalling and vasodilation. Impaired NO bioavailability represents the central feature of endothelial dysfunction associated with vascular diseases. Interestingly, dietary supplementation with L-arginine has been shown to alleviate endothelial dysfunctions caused by impaired NO synthesis. In this study the transport kinetics of [3H]-arginine and [3H]-ADMA into the central nervous system (CNS) were investigated using physicochemical assessment and the in situ brain/choroid plexus perfusion technique in anesthetized mice. Results indicated that L-arginine and ADMA are tripolar cationic amino acids and have a gross charge at pH 7.4 of 0.981. L-Arginine (0.00149 +/- 0.00016) has a lower lipophilicity than ADMA (0.00226 +/- 0.00006) as measured using octanol-saline partition coefficients. The in situ perfusion studies revealed that [3H]-arginine and [3H]-ADMA can cross the blood-brain barrier (BBB) and the blood-CSF barrier. [3H]-Arginine (11.6nM) and [3H]-ADMA (62.5nM) having unidirectional transfer constants (Kin) into the frontal cortex of 5.84 +/- 0.86 and 2.49 +/- 0.35 ml.min-1.g-1, respectively, and into the CSF of 1.08 +/- 0.24 and 2.70 +/- 0.90 ml.min-1.g-1, respectively. In addition, multiple-time uptake studies revealed the presence of CNS-to-blood efflux of ADMA. Self- and cross-inhibition studies indicated the presence of transporters at the BBB and the blood-CSF barriers for both amino acids, which were shared to some degree. Importantly, these results are the first to demonstrate: (i) saturable transport of [3H]-ADMA at the blood-CSF barrier (choroid plexus) and (ii) a significant CNS to blood efflux of [3H]-ADMA. Our results suggest that the arginine paradox, in other words the clinical observation that NO-deficient patients respond well to oral supplementation with L-arginine even though the plasma concentration is easily sufficient to saturate endothelial NOS, could be related to ADMA transport.

A temporally restricted function of the Dopamine receptor Dop1R2 during memory formation
Dopamine is a crucial neuromodulator, which is involved in many brain processes, including learning and the formation of memories. Dopamine acts through multiple receptors and controls an intricate signaling network to regulate different tasks. While the diverse functions of dopamine are intensely studied, the interplay and role of the distinct dopamine receptors to regulate different processes is less well understood. An interesting candidate is the dopamine receptor Dop1R2 (also known as Damb), as it could connect to different downstream pathways. Dop1R2 is reported to be involved in forgetting and memory maintenance, however, the circuits requiring the receptors are unknown. To study Dop1R2 and its role in specific spatial and temporal contexts, we generated a conditional knock-out line using the CRISPR-Cas9 technique. Two FRT sites were inserted, allowing flippase-mediated excision of the dopamine receptor in neurons of interest. To study the function of Dop1R2, we knocked it out conditionally in the Mushroom body of Drosophila melanogaster, a well-studied brain region for memory formation. We show that Dop1R2 is required for later memory forms but not for short-term memories for both aversive and appetitive memories. Moreover, Dop1R2 is specifically required in the the alpha/beta-lobe and the alpha/beta-lobe but not in the gamma-lobe of the Mushroom body. Our findings show a spatially and temporally restricted role of Dop1R2 in the process of memory formation highlighting the differential requirement of receptors during distinct phases of learning.

Endocytic adaptor AP-2 maintains Purkinje cell function by balancing cerebellar parallel and climbing fiber synapses
The selective loss of cerebellar Purkinje cells is a hallmark of various neurodegenerative movement disorders, yet the precise mechanism driving their degeneration remains enigmatic. Here we show that the endocytic adaptor protein complex 2 (AP-2) is essential for the survival of Purkinje cells. Employing a multidisciplinary approach encompassing mouse genetics, viral tracing, ex vivo calcium imaging, and kinematic analysis, we demonstrate that mice lacking the -subunit of AP-2 in cerebellar Purkinje cells exhibit early-onset ataxia associated with progressive Purkinje cell degeneration. Importantly, we uncover that synaptic input dysfunctions, characterized by a predominance of parallel fiber (PF) over climbing fiber (CF) synapses precede Purkinje cell loss. Mechanistically, we find that AP-2 localizes to Purkinje cells dendrites, where it interacts with the PF synapse-enriched protein GRID2IP. The loss of AP-2 results in proteasome-dependent degradation of GRID2IP and accumulation of the glutamate {delta}2 receptor (GLUR{delta}2) in distal Purkinje cell dendrites, leading to an excess of PF synapses, while CF synapses are drastically reduced. The overrepresentation of PF synaptic input induces Purkinje cell hyperexcitation, which can be alleviated by enhancing synaptic glutamate clearance using the antibiotic ceftriaxone. Our findings demonstrate the critical role of AP-2 in preventing motor gait dysfunctions by regulating GRID2IP levels in Purkinje cells, thereby preserving the equilibrium of PF and CF synaptic inputs in a cell-autonomous manner.