bioRxiv Subject Collection: Neuroscience's Journal

TARP γ-8 is a target of ethanol that regulates self-administration and relapse in mice
Background: Behavioral pathologies that characterize alcohol use disorder (AUD) are driven by the powerful reinforcing, or rewarding, properties of the drug. We have shown that glutamate AMPA receptor (AMPAR) activity is both necessary and sufficient for alcohol (ethanol) reinforcement. Transmembrane AMPAR regulatory protein (TARP) {gamma}-8 is an essential auxiliary protein that regulates AMPAR expression and activity; however, the role of TARP {gamma}-8 in AUD or other forms of addiction remains largely unexplored. Objectives: This study investigated the mechanistic role of TARP {gamma}-8 in operant ethanol self-administration (model of primary reinforcement) and cue-induced reinstatement of ethanol-seeking behavior (model of conditioned reinforcement) using TARP {gamma}-8 heterozygous null (+/-) mice. To determine if TARP {gamma}-8 signaling is targeted by ethanol use, we evaluated protein expression of TARP {gamma}-8, GluA1, CaMKII, and PSD-95 following ethanol self-administration. Results: A battery of tests evaluating food and water intake, taste reactivity, anxiety-like behavior, and object recognition memory showed no fundamental behavioral deficits in TARP {gamma}-8(+/-) mice, and no differences in response to acute ethanol or home-cage drinking as compared to wild-types. However, TARP {gamma}-8(+/-) mice exhibited significantly reduced acquisition and escalation of operant ethanol self-administration and reduced cue-induced reinstatement of ethanol-seeking behavior, with no differences in parallel sucrose-only controls. In wild-type mice, ethanol self-administration increased TARP {gamma}-8 expression in the amygdala, nucleus accumbens, and hippocampus, and increased GluA1 expression in the amygdala and prefrontal cortex, compared to sucrose controls. Conclusion: These findings highlight the specificity of TARP {gamma}-8 regulation of ethanol reinforcement mechanisms and identify this crucial AMPAR auxiliary protein as a target of ethanol in reward-related brain regions, highlighting its potential for development of novel pharmacotherapies for AUD.

Sex-specific proteomic analysis of epileptic brain tissues from Pten knockout mice and human refractory epilepsy
Rationale: Epilepsy presents significant sex-based disparities in prevalence and manifestation. Epidemiological studies reveal that epilepsy is more prevalent in males, with lesional types being more common, whereas idiopathic generalized epilepsies are more frequently observed in females. These differences stress the importance of considering sex-specific factors in epilepsy diagnosis, treatment, and mechanistic research using preclinical models. To elucidate potential molecular differences that could explain these disparities and inform personalized treatment strategies, we conducted a proteomic analysis of epileptic brain tissues from both an experimental mouse model of genetic epilepsy and humans with drug-resistant epilepsy (DRE). Methods: We employed mass spectrometry-based proteomic analysis on brain tissues from DRE patients and the Pten knockout (KO) mouse model of genetic epilepsy with focal cortical dysplasia. Mouse samples included hippocampi from adult wild-type (WT) and Pten KO mice (4-5 per group and sex). Human samples included temporal cortex from 12 DRE adult patients (7 males, 5 females) and 5 non-epileptic (NE) controls (2 males, 3 females). Brain biopsies were collected with patients' informed consent under approved IRB protocols (Indiana University Health Biorepository). Proteomic profiles were analyzed using principal component analysis (PCA) along with volcano plots to identify significant changes in protein expression. The enrichment analysis of differentially expressed proteins was conducted by Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway. Results: PCA revealed distinct clustering of brain proteomes between epilepsy and control cases in both human and mice, with 390 proteins showing significant differences in human and 437 proteins in mouse samples. These proteins are primarily associated with ion channels, synaptic processes, and neuronal energy regulation. In the mouse model, males have more pronounced proteomic changes than females, with enrichment in metabolic pathways and VEGF signaling pathway, indicating a more severe vascular permeability impairment in males. In human DRE cases, 118 proteins were significantly changed by comparing epileptic females to males. Pathway analysis revealed changes in metabolic pathways and the HIF-1 signaling pathway, indicating that altered neuronal activity and inflammation may lead to increased oxygen consumption. Conclusion: These findings highlight significant differences between epilepsy and control brain samples in both humans and mice. Sex-specific analysis revealed distinct pathway enrichments between females and males, with males exhibiting a broader range of alterations, suggesting more extensive proteomic alterations. This study offers valuable insights into potential underlying mechanisms of epilepsy and underscores the importance of considering sex as a key factor in epilepsy research and therapeutic development.

Ethological profiling of pain and analgesia in a mouse model of complex regional pain syndrome.
Complex regional pain syndrome (CRPS) is a form of chronic post-injury pain affecting the extremities. The mouse tibial fracture-cast model was developed to enable preclinical study of CRPS mechanisms and guide condition-specific drug development. Given the inherent limitations of reflex pain measures in mice, we sought to characterize pain-like behaviors in this model more holistically. We evaluated spontaneous and evoked pain and naturalistic behaviors after tibial fracture-cast injury in male mice in neutral and aversive environments using LabGym. Here, we report a unique ethological signature of pain in injured mice characterized by reflexive allodynia, thermal hyperalgesia, frequent grooming and reduced rearing in neutral and aversive environments, and decreased paw withdrawal and increased paw licking in an aversive environment. As proof-of-concept, we also leveraged this holistic behavioral evaluation for drug screening by characterizing the peripheral versus central effects of targeting alpha-2 receptors (2-AR) in the tibial fracture-cast model. We evaluated the impact of systemic delivery of dexmedetomidine (DEX), a selective 2-AR agonist, with or without antagonists, on holistic behavioral metrics in injured male mice. We found that DEX reduced mechanical allodynia primarily via central 2-ARs. DEX also decreased motion metrics, grooming and rearing in an open field, and distinctly affected the quality and quantity of grooming in an aversive environment, and this effect was not suppressed by systemic 2-AR antagonists. Ultimately, this study holistically captures pain-related behaviors and provides a detailed characterization of the relative contributions of peripheral and central 2-ARs to alpha2-mediated analgesia in male mice after tibial fracture-cast injury.

Evidence for cPLA2 activation in Alzheimer's Disease Synaptic Pathology
Background Synapses are essential for learning and memory, and their loss predicts cognitive decline in Alzheimer's disease (AD). Synaptic loss is associated with excitotoxicity, neuroinflammation, amyloid-{beta}, and tau pathology, but the molecular mechanisms remain unclear. There is an urgent need to identify new targets to modify the disease and slow synaptic loss and cognitive decline. This study examines if calcium-dependent phospholipase A2 (cPLA2) is implicated in AD synaptic loss. cPLA2 catalyzes membrane phospholipids to release arachidonic acid, which can be metabolized into inflammatory eicosanoids. Methods cPLA2 levels were examined in synaptosomes isolated from the postmortem frontal cortex of individuals with no cognitive impairment (NCI), mild cognitive impairment (MCI), and AD dementia from the Religious Orders Study (ROS). Eicosanoids in synaptosomes were analyzed using lipidomics. Immunofluorescent staining investigated cPLA2 interactions with synaptic markers. Human iPSCs-derived neurons were used to study cPLA2 overactivation after exposure to amyloid-{beta} 42 oligomers (A{beta}42O), its relationships with synaptic markers, and the effects of cPLA2 inhibitors. Results We observed elevated cPLA2 (cPLA2 and cPLA2{beta}) in AD synaptosomes and positive correlations with postsynaptic density protein 95 (PSD-95) and cognitive dysfunction. Eicosanoids were increased in AD synaptosomes and correlated with cPLA2, indicating cPLA2 activity at synapses/synaptosomes. Phosphorylated cPLA2(p-cPLA2) colocalized with PSD-95 in synaptosomes, and with postsynaptic Ca2+/calmodulin-dependent protein kinase II (CaMKII) and dendritic microtubule-associated protein 2 (MAP2) in NCI and AD brains, where their levels were reduced in AD. P-cPLA2 colocalizes with MAP2 at the neuronal soma associated with neuritic plaques and neurodegeneration in AD. A{beta}42O activates cPLA2 in human iPSCs-derived neurons, leading to p-cPLA2 relocation from the cytosol to synaptic and dendritic sites to colocalize with CaMKII and MAP2, resulting in their reduction. P-cPLA2 also colocalized with PSD-95 in A{beta}42O-exposed neurons, accompanied with increased PSD-95 intensity at soma membrane. These processes were reversed by the cPLA2 inhibitor ASB14780. Conclusions cPLA2 overactivation at synapses, dendrites, and excitatory neuronal somas is associated with synaptic loss, neuritic plaques and neurodegeneration, potentially contributing to cognitive decline in AD. Future research needs to explore the role of cPLA2 as a disease-modifying target for AD.

Ketamine inhibition of SARS-CoV-2 replication in astrocytes is associated with COVID-19 disease severity in a variant-dependent manner
Severe coronavirus infections, including SARS-CoV-2, can cause neurological symptoms, but the underlying neurotropic mechanisms are unclear. Experiments with SARS-CoV-2 variants B.1.258.17, B.1.1.7, and BA.5.3.2 (termed wild-type, alpha and omicron, respectively) revealed that human astrocytes, not neurons, support viral proliferation. During the COVID-19 pandemic, new virus variants exhibited milder disease progression. A retrospective study of patients with COVID-19 infected by wild-type or alpha variants was conducted to test whether ketamine, an anaesthetic that inhibits endocytosis, affects COVID-19. At admission, patients infected with the wild-type showed greater disease severity than alpha variant patients, but the disease course was similar. This may be due to distinct ketamine-mediated SARS-CoV-2 variant-dependent effects, revealing stronger ketamine inhibition of the wild-type variant than the alpha variant mediating astrocyte responses involving the expression of ACE2, a viral cell entry site, viral proteins RNA-dependent RNA polymerase and envelope protein-E in infected cells. Overexpression of SARS-CoV-2 protein 3a attenuated astroglial lysosomal traffic, and 3a and nsp6 differentially modulated lipid droplet accumulation and initiation of autophagy, where ketamine predominantly affected vesicle dynamics. In summary, human astrocytes, but not neurons, contribute to SARS-CoV-2 neurotropism, highlighting the potential benefits of ketamine treatment in coronavirus infections.

MiR-126 Improves the Therapeutic Effect of EPC in Hypertensive Ischemic Stroke
Background and Purpose: Hypertension promotes circulatory endothelial inflammation, reduces endothelial progenitor cell (EPC) function, and impairs their therapeutic potential following ischemic stroke. MiR-126 is known to regulate vascular development and angiogenesis. This study investigates the therapeutic potential of miR-126 by overexpressing it in EPCs to enhance their efficacy in hypertensive stroke conditions. Methods: Adult spontaneously hypertensive rats (SHRs, n=118) underwent permanent suture middle cerebral artery occlusion (MCAO) to induce ischemic stroke. One week post-stroke, animals were injected with EPCs overexpressing miR-126 or control EPCs. Treatment effects were evaluated over 35 days, using neurological scoring, infarct volume measurements, behavioral testing, and assessments of neuroinflammation, blood pressure, and angiogenesis. Exosomes from miR-126 overexpressing EPCs were isolated and analyzed for mechanistic studies. Results: In vitro, miR-126 enhanced EPC angiogenic function under stress. In vivo, miR-126 modified EPC treatment improved functional recovery, reduced infarct volume, and promoted angiogenesis compared to controls in SHRs. Furthermore, miR-126 treatment preserved the blood-brain barrier, reduced peripheral immune cell infiltration, and modulated neuroinflammation. Exosomes derived from miR-126 overexpression EPCs also promoted angiogenesis and reduced endothelial activation under stress conditions. Conclusions: EPC overexpressing miR-126 provides neuroprotection by enhancing angiogenesis, reducing ischemic injury, and preserving blood-brain barrier integrity in hypertensive stroke models. This approach modulates neuroinflammation and improves neurological outcomes, suggesting gene-modified EPCs as a promising strategy for ischemic stroke therapy, particularly under hypertensive conditions.

Relevance of Nonlinear Dimensionality Reduction for Efficient and Robust Spike Sorting
Spike sorting is one of the cornerstones of extracellular electrophysiology. By leveraging advanced signal processing and data analysis techniques, spike sorting makes it possible to detect, isolate, and map single neuron spiking activity from both in vivo and in vitro extracellular electrophysiological recordings. A crucial step of any spike sorting pipeline is to reduce the dimensionality of the recorded spike waveform data. Reducing the dimensionality of the processed data is mandatory to apply the clustering algorithms responsible for detecting, isolating, and sorting the recorded putative neurons. In this paper we propose and illustrate on both synthetic and experimental data that employing the nonlinear dimensionality reduction technique Uniform Manifold Approximation and Projection can drastically improve the performance, efficiency, robustness, and scalability of spike sorting pipelines without increasing their computational cost. We show how replacing the linear or expert-defined dimensionality reduction methods commonly used in spike sorting pipelines by unsupervised, mathematically grounded, nonlinear methods increases the number of correctly sorted neurons, makes the identification of quieter, seldom spiking neurons more reliable, enables deeper and more precise explorations and analysis of the neural code, and paves new ways toward more efficient and end-to-end automatable spike sorting pipelines of large-scale extracellular neural recording as those produced by high-density multielectrode arrays.

Testosterone differentially modulates the display of agonistic behavior and dominance over opponents before and after adolescence in male Syrian hamsters
The current study investigated the influence of testosterone on agonistic behavior and dominance over an opponent before and after adolescence in male Syrian hamsters (Mesocricetus auratus). We hypothesized that testosterone-dependent modulation of agonistic behavior would be greater following adolescent development. To test this hypothesis, prepubertal (14 days of age) and adult subjects (52-62 days of age) were gonadectomized and immediately implanted with testosterone or vehicle pellets. Fourteen days later, agonistic behavior was assessed in a neutral arena with age-matched testosterone-treated opponents. Flank marking was also assessed separately in response to male odors alone. Our hypothesis predicted that testosterone would modulate agonistic behavior and dominance over an opponent in adult but not in prepubertal subjects, however, only flank marking behavior followed the predicted data pattern. During both social interaction and scent tests, testosterone increased flank marking behavior in adults, but failed to increase flank marking in prepubertal subjects. Contrary to our predictions, testosterone treatment increased prepubertal subject attacks, decreased submissive tail-up displays, and facilitated prepubertal subject dominance over opponents. In adults, testosterone increased paws-on investigation and flank marking during social interactions. Taken together, these data indicate that some, but not all aspects of agonistic behavior are sensitive to the activational effects of testosterone prior to adolescence, and that activational effects of testosterone differ substantially between prepubertal and adult males. Our results may have implications for early pubertal timing and increased risk for externalizing symptoms and aggressive behavior in humans.

Translating brain anatomy and neurodegenerative disease from mouse to human through latent gene expression space
The mouse model is by far the most widely used animal model in preclinical neuroscience, but translating findings to humans suffers from the lack of a formal framework establishing the correspondence between the mouse and the human brain. In this study, we build on the concept of common brain space, and on previous work embedding gene expression profiles, to bring the two species into alignment for comparative analysis. Using a variational autoencoder (VAE) combined with a latent classifier, we create a latent space that strikes a balance between abstract features related to reconstruction and features pertaining to regional segregation. This approach demonstrates improved cross-species homology and within-species locality compared to existing comparative models. In addition, we show that brain alterations in mouse disease models can be translated to humans, predicting patterns of brain changes in Alzheimer's and Parkinson's diseases. The flexibility and scalability of this approach offer a promising framework to bridge between more animal models, comparing quantitative imaging modalities, and disease phenotypes. This in turn will help advance our understanding of species similarities and differences, enhancing both fundamental translational neuroscience and disease modelling.

Decoding the Human Brain during Intelligence Testing
Understanding the mechanisms of the human brain enabling complex cognition is a major objective of neuroscientific research. Studies employing functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) identified increased activation in specific brain regions during different cognitive states. However, the neural processes during the performance of an intelligence test remains largely unknown. This study considers intelligence as a whole-brain network phenomenon and investigates how the connectedness of specific brain regions contributes to performance on the Raven Progressive Matrices (RAPM), a well-established intelligence test. Connectedness was characterized with graph-theoretical measures based on functional connectivity derived from fMRI BOLD (N=67) and EEG theta-band (N=128) activity. The results reveal that the extent to which specific frontal and parietal regions are connected to other brain systems during intelligence testing relates to individual test performance. These regions may act as controllers, enabling flexible and efficient switches between cognitive states required to excel in intelligence tests.

Concurrent multimodal measurement of excitation and inhibition shows that EEG-based estimates are linked to the ratio of glutamate to GABA
Neural excitation/inhibition (E/I) balance is dynamically regulated on multiple timescales. Adaptive changes in E/I balance changes can support healthy development, learning, and cognition, while disordered E/I balance is implicated in neurodevelopmental disorders, neurodegenerative disorders, and states of impaired vigilance. There has been growing interest in inferring E/I balance from efficient and noninvasive measurements such as electroencephalography (EEG), and several algorithms have been proposed to estimate E/I balance from EEG recordings. Despite promising results, there has been a lack of validation studies testing the underlying neurochemical changes leading to increased or decreased EEG-based E/I. Here we assess E/I balance with concurrent EEG and magnetic resonance spectroscopy (MRS) in humans. We estimate a standard measure of E/I balance, glutamate concentration divided by GABA concentration, and assess the correspondence between each candidate EEG-based E/I algorithm to this MRS-based estimate. Due to the methodological interest in both between-subjects research (e.g., comparing disordered to healthy E/I) as well as within-subjects research (e.g., comparing pre-intervention to post-intervention E/I), we quantify the associations between EEG-based E/I and MRS-based E/I separately for between-subjects and within-subjects comparisons. We find that each EEG-based E/I algorithm shows reliable and positive associations with MRS-based E/I. While these associations are evident for between-subjects comparisons, they are quite weak for within-subjects comparisons. Candidate EEG-based E/I algorithms are thus likely to be reflecting, at least in part, relative concentrations of cortical glutamate and GABA, although poor signal quality appears to limit these methods when attempting to increase temporal precision and identify within-subjects variations.

Released mitochondrial DNA and neurofilament light chain as Parkinson's disease phenotypes in patient-specific midbrain assembloids
Parkinson's Disease is the second most common neurodegenerative disorder worldwide, with growing numbers and considerable societal and economic concerns. Human cell culture systems are efficient models for neurodegenerative disorders and allow for personalized, non-invasive analysis of cellular and molecular disease mechanisms. Midbrain organoids and assembloids are advanced 3D culture systems that recapitulate the human midbrain, which is highly affected by Parkinson's disease. Here, we used healthy control and patient-specific midbrain assembloids to assess mitochondrial DNA phenotypes and NfL levels alongside neurodegeneration and alpha-synuclein phosphorylation. Importantly, alterations in mitochondrial DNA homeostasis and NfL levels can be assayed in the supernatant and therefore are particularly suitable as biomarkers and for high throughput screening approaches.

A canonical cortical electronic circuit for neuromorphic intelligence
Cortical microcircuits play a fundamental role in natural intelligence. While they inspired a wide range neural computation models and artificial intelligence algorithms, few attempts have been made to directly emulate them with an electronic computational substrate that uses the same physics of computation. Here we present a heterogeneous canonical microcircuit architecture compatible with analog neuromorphic electronic circuits that faithfully reproduce the properties of real synapses and neurons. The architecture comprises populations of interacting excitatory and inhibitory neurons, disinhibition pathways, and spike-driven multi=compartment dendritic learning mechanisms. By co-designing the computational model with its neuromorphic hardware implementation, we developed a neural processing system that can perform complex signal processing functions, learning, and classification tasks robustly and reliably, despite the inherent variability of the analog circuits, using ultra-low power energy consumption features comparable to those of their biological counterparts. We demonstrate how both the model architecture and its hardware implementation seamlessly capture the hallmarks of neural computation: attractor dynamics, adaptation, winner-take-all behavior, and resilience to variability, within a compact, low-power computing substrate. We validate the model's learning performance both from the algorithmic perspective and with detailed electronic circuit simulation experiments and characterize its robustness to noise. Our results illustrate how local, biologically plausible rules for plasticity and gating can overcome challenges like catastrophic forgetting and parameter variability, enabling effective always-on adaptation. Beyond offering insights into the nature of computation in neural systems, our approach introduces a foundation for ultra-low power, fault-tolerant architectures capable of complex signal processing at the edge. By embracing -rather than mitigating- variability, these neuromorphic circuits exhibit a powerful synergy with emerging memory technologies, suggesting a new paradigm for sophisticated "in-memory" computing. Through such tight integration of neuroscience principles and analog circuit design, we pave the way toward a class of brain-inspired processors that can learn continuously and respond dynamically to real-world inputs.

The speed of information processing at memory competitions: limited by reading in short tasks and declining as a power law for longer times
We analyze information rates associated with top performances in memory competitions and reveal three phenomena. First, in tasks with short memorization time, information processing reaches up to 42 bit/s with most of the time spent on reading, suggesting that mental associations are formed even more rapidly. Second, record performances show a remarkable concordance across time scales: the processing speed depends on memorization time as a power law. Third, despite dramatic improvements in scores and mnemonic strategies over the last decades, the differences in information rates across memorization tasks remain remarkably consistent.

Olfactory dysfunction in a novel model of prodromal Parkinson's disease in adult zebrafish
Olfactory dysfunction is a clinical marker of prodromal Parkinson's disease (PD), a neurodegenerative disorder characterized by severe motor impairments. Although common, the mechanisms linking PD and olfactory dysfunction remain unclear. To explore this relationship, we developed a model of olfactory dysfunction that recapitulates the prodromal stage of PD without affecting motor function. For this, we used zebrafish, an animal model widely used in PD research that shares olfactory system similarities with mammals and that exhibits unique regenerative capabilities. By injecting 6-hydroxydopamine (6-OHDA) into the dorsal telencephalic ventricle, we observed a significant loss of dopaminergic periglomerular neurons in the olfactory bulb (OB) and retrograde degeneration of olfactory sensory neuron (OSN) in the peripheral olfactory epithelium (OE). These alterations led to impaired olfactory responses to the aversive odorant, cadaverine, although olfactory responses to alanine, an attractive odorant, were not impaired. 6-OHDA triggered a neuroinflammatory response, which was reduced by treatment with the anti-inflammatory drug pranlukast. By 7 dpi, we observed remodeling of dopaminergic synapses in the OB and restoration of the OE, along with a resolution of the neuroinflammatory response. By this time, olfactory responses to cadaverine were fully restored, highlighting the remarkable neuroplasticity of the zebrafish olfactory system. This novel model of prodromal PD could offer valuable insights into the early stages and progression of this neurodegenerative disease and increase our understanding of the relationship between dopaminergic loss and olfactory dysfunction.

Alternative splicing generates a Ribosomal Protein S24 isoform induced by neuroinflammation and neurodegeneration
Neuroinflammation, particularly that involving reactive microglia, the brain's resident immune cells, is implicated in the pathogenesis of major neurodegenerative diseases. However, early markers of this process are in high demand. Multiple studies have reported changes in ribosomal protein (RP) expression during neurodegeneration, but the significance of these changes remains unclear. Ribosomes are evolutionarily conserved protein synthesizing machines, and although commonly viewed as invariant, accumulating evidence suggest functional ribosome specialization through variation in their protein composition. By analyzing cell type-specific translating mRNAs from mouse brains, we identify distinct RP expression patterns between neurons, astrocytes, and microglia, including neuron-specific RPs, Rpl13a and Rps10. We also observed complex expression relationships between RP paralogs and their canonical counterparts, suggesting regulated mechanisms for generating heterogeneous ribosomes. Analysis across brain regions revealed that Rplp0 and Rpl13a, commonly used normalization references, show heterogeneous expression, raising important methodological considerations for gene expression studies. Importantly, we show that Rps24, an essential ribosome component that undergoes alternative splicing to produce protein variants with different C-termini, exhibits striking cell type-specific isoform expression in brain. The Rps24c isoform is predominantly expressed in microglia and is increased by neuroinflammation caused by aging, neurodegeneration, or inflammatory chemicals. We verify increased expression of S24-PKE, the protein variant encoded by Rps24c, in brains with Alzheimer's disease, Parkinson's disease, and Huntington's disease, and relevant mouse models, using isoform-specific antibodies. These findings establish heterogeneous RP expression as a feature of brain cell types and identify Rps24c/S24-PKE as a novel marker for neuroinflammation and neurodegeneration.

Substrate stiffness and shear stress collectively regulate the inflammatory phenotype in cultured human brain microvascular endothelial cells
Brain endothelial cells experience mechanical forces in the form of blood flow-mediated shear stress and underlying matrix stiffness, but intersectional contributions of these factors towards blood-brain barrier (BBB) impairment and neurovascular dysfunction have not been extensively studied. Here, we developed in vitro models to examine the sensitivity of primary human brain microvascular endothelial cells (BMECs) to substrate stiffness, with or without exposure to fluid shear stress. Using a combination of molecular profiling techniques, we show that BMECs exhibit an inflammatory signature at both the mRNA and protein level when cultured on gelatin substrates of intermediate stiffness (~30 kPa) versus soft substrates (~6 kPa). Exposure to modest fluid shear stress (1.7 dyne/cm2) partially attenuated this signature, including reductions in levels of soluble chemoattractants and surface ICAM-1. Overall, our results indicate that increased substrate stiffness promotes an inflammatory phenotype in BMECs that is dampened in the presence of fluid shear stress.

Striatal neural ensemble codes for voluntary locomotor and involuntary dyskinetic movements
Classical models of movement control posit that striatal spiny projection neurons of the basal ganglia's direct and indirect pathways (dSPNs and iSPNs) respectively promote and suppress movement. Supporting this view, physiological recordings have revealed imbalanced dSPN and iSPN activity levels during hypokinetic and hyperkinetic movement conditions. However, in normal brain states, dSPN and iSPN ensembles have approximately equal activation amplitudes and time courses, jointly encoding specific actions. How pathological movement conditions alter such action coding remains poorly understood. Here we imaged the concurrent dynamics of dSPNs and iSPNs in behaving mice across normal, hypokinetic, and hyperkinetic conditions, before and after administration of drug treatments used clinically. Analyses focused on resting periods and neural activity that immediately preceded movement, examining how SPNs encoded upcoming actions. In hypokinetic states, the dSPN population was hypoactive relative to the iSPN population, consistent with prior reports. Moreover, individual dSPNs and iSPNs that encoded upcoming locomotion exhibited a reduced measure of activity compared to the normal state; the extent of this reduction predicted the degree of decline in the occurrence of locomotion. Levodopa (L-DOPA) and amantadine treatments both improved locomotion frequency but acted via distinct mechanisms. L-DOPA rebalanced the activity of the dSPN and iSPN populations, whereas amantadine boosted the activity of individual locomotion-related dSPNs and iSPNs. In hyperkinetic states modeling L-DOPA-induced dyskinesia, dSPN populations were hyperactive relative to iSPN populations. Involuntary dyskinetic movements engaged individual dSPNs and iSPNs distinct from those encoding voluntary locomotion. Amantadine treatment reduced the resting activity of dyskinesia- but not locomotion-related SPNs without improving the overall dSPN and iSPN imbalance. These findings highlight the importance of SPN action coding, not merely the extent of activity balance, for normal and pathological movements. The results delineate two distinct therapeutic mechanisms, one that rebalances the activity of the direct and indirect pathways and another that selectively potentiates or depresses the activity of SPN populations encoding voluntary or involuntary actions. Overall, this study refines the understanding of striatal dysfunction in movement disorders, demonstrates that distinct neural populations underlie normal voluntary locomotion and involuntary dyskinetic movements, and defines two complementary routes for the development of symptomatic treatments.

Neural activation down to the spinal cord during action language? A transcranial magnetic stimulation and peripheral nerve stimulation study.
Language comprehension is increasingly recognized as extending beyond the traditional linguistic system to engage motor and perceptual processes. This perspective is supported by numerous studies demonstrating that understanding action-related words often induces behavioral and neurophysiological changes in the motor system. However, it remains unclear whether the influence of action language on the motor system is restricted to cortical regions, or whether it also extends to spinal structures, as observed during motor imagery. To address this, we used transcranial magnetic stimulation and peripheral nerve stimulation to assess corticospinal excitability and cortico-motoneuronal transmission, respectively. Fifteen healthy and right-handed volunteers participated in four conditions: (i) rest, (ii) kinesthetic motor imagery of finger and wrist flexion, (iii) reading action sentences, and (iv) reading non-action sentences. As anticipated, corticospinal excitability increased during both kinesthetic motor imagery and action reading compared to rest. Interestingly, while kinesthetic motor imagery also led to the expected increase in cortico-motoneuronal transmission, no such modulation occurred during action reading. These findings suggest that action reading do not modulate the excitability of high-threshold motoneurons at the spinal level, contrary to motor imagery. Further investigation is needed to test whether action reading activate lower-threshold spinal structures, such as interneurons involved in spinal pre-synaptic inhibition.

Casein kinase 1δ-regulated formation of GVBs induces resilience to tau pathology-mediated protein synthesis impairment
In Alzheimers disease, many surviving neurons with tau pathology contain granulovacuolar degeneration bodies (GVBs), neuron-specific lysosomal structures induced by pathological tau assemblies. This could indicate a neuroprotective role for GVBs, however, the mechanism of GVB formation and its functional implications are elusive. Here, we demonstrate that GVB formation depends on CK1delta activity and basal autophagy. We show that neurons with GVBs (GVB+) are resilient to tau-induced impairment of global protein synthesis and are protected against tau-mediated neurodegeneration. GVB+ neurons have multiple adaptations to counteract the tau pathology-induced decline in protein synthesis, including increased ribosomal content. Importantly, unlike neurons without GVBs, GVB+ neurons fully retain the capacity to induce long-term potentiation-induced protein synthesis in the presence of tau pathology. Our results have identified CK1delta as a key regulator of GVB formation that confers a protective neuron-specific proteostatic stress response to tau pathology. Our findings provide novel opportunities for targeting neuronal resilience in tauopathies.