bioRxiv Subject Collection: Neuroscience's Journal

Altricial brains and the evolution of infant vocal learning
Human infant vocal development is strongly influenced by interactions with caregivers who reinforce more speech-like sounds. This trajectory of vocal development in humans is radically different from those of our close phylogenetic relatives, Old World monkeys and apes. In these primates most closely related to humans on the evolutionary tree, social feedback plays no significant role in their vocal development. Oddly, infant marmoset monkeys, a more distantly related New World primate, do exhibit socially guided vocal learning. To explore what developmental mechanism could have evolved to account for these behavioral differences, we hypothesized that the evolution of human and marmoset vocal learning in early infancy in both species is because they are born neurally altricial relative to other primate and in a cooperative breeding social environment. Our analysis found that, indeed, human and marmoset brain are growing faster at birth when compared with chimpanzees and rhesus macaques, making them altricial relative to these primates. We formalized our hypothesis using a logistic growth model showing that the maturation of a system dependent on the rate of brain growth and the amount of social stimuli benefits from an altricial brain and a cooperative breeding environment. Our data suggest that in primates, the evolution of socially guided vocal learning during early infancy in humans and marmosets was afforded by infants with a relatively altricial brain and behavior, sustained and stimulated by cooperative breeding environments.

Neural dynamics in the orbitofrontal cortex reveal cognitive strategies
Behavior is sloppy: a multitude of cognitive strategies can produce similar behavioral read-outs. An underutilized approach is to combine multifaceted behavioral analyses with neural recordings to resolve cognitive strategies. Here we show that rats performing a decision-making task exhibit distinct strategies over training, and these cognitive strategies are decipherable from orbitofrontal cortex (OFC) neural dynamics. We trained rats to perform a temporal wagering task with hidden reward states. While naive rats passively adapted to reward statistics, expert rats inferred reward states. Electrophysiological recordings and novel methods for characterizing population dynamics identified latent neural factors that reflected inferred states in expert but not naive rats. In experts, these factors showed abrupt changes following single trials that were informative of state transitions. These dynamics were driven by neurons whose firing rates reflected single trial inferences, and OFC inactivations showed they were causal to behavior. These results reveal the neural signatures of inference.

BT-11 repurposing potential for Alzheimer's disease and insights into its mode of actions
Neuroinflammation is a key pathological hallmark of Alzheimer's disease (AD). Investigational and FDA approved drugs targeting inflammation already exist, thus drug repurposing for AD is a suitable approach. BT-11 is an investigational drug that reduces inflammation in the gut and improves cognitive function. BT-11 is orally active and binds to lanthionine synthetase C-like 2 (LANCL2), a glutathione-s-transferase, thus potentially reducing oxidative stress. We investigated the effects of BT-11 long-term treatment on the TgF344-AD rat model. BT-11 reduced hippocampal-dependent spatial memory deficits, A{beta} plaque load and neuronal loss in males, and mitigated microglia numbers in females. BT-11 treatment led to hippocampal transcriptomic changes in signaling receptor, including G-protein coupled receptor pathways. We detected LANCL2 in hippocampal nuclear and cytoplasmic fractions with potential different post-translational modifications, suggesting distinct functions based on its subcellular localization. LANCL2 was present in oligodendrocytes, showing a role in oligodendrocyte function. To our knowledge, these last two findings have not been reported. Overall, our data suggest that targeting LANCL2 with BT-11 improves cognition and reduces AD-like pathology by potentially modulating G-protein signaling and oligodendrocyte function. Our studies contribute to the field of novel immunomodulatory AD therapeutics, and merit further research on the role of LANCL2 in this disease.

Neurodegeneration impairs the consolidation of developmentally synchronized behavioral patterns
Animals generate predictable patterns of behavior that are robustly synchronized with the developmental clock. However, the long-term establishment of time-locked behaviors across development, and the neuronal alterations that may impair them, remain underexplored. Here, by quantifying the temporal synchronization of behavior in multiple isolated C. elegans individuals throughout their complete development time, we show that robust behavioral synchronization consolidates across stages as development progresses. Analyses of multiple mutant populations with perturbed neuronal function or structure reveal that neurodegeneration in specific circuits impairs the developmental organization of behavior. In one of the cases, protection from neurodegeneration of the circuit of touch receptor neurons restored normal modes of long-term behavior. Moreover, at the neuronal activity level, we found altered activity patterns in downstream motor neurons following neurodegeneration. These results suggest the impairment of developmental patterns of synchronized behavior by localized neurodegenerative processes within the nervous system.

How relevant is the prior? Bayesian causal inference for dynamic perception in volatile environments
Our brains predict future sensory input based on their current beliefs about the world around us, but interpreting prediction errors can be challenging in a volatile environment because they can be caused by stochastic noise or by outdated predictions. Noisy signals should be integrated with prior beliefs to improve precision, but the two should be segregated when environmental changes render prior beliefs irrelevant. Bayesian inference provides a statistically optimal solution to deal with situations in which there is uncertainty about the cause of the prediction errors. However, the method quickly becomes memory intensive and computationally intractable when applied consecutively. Here, we systematically evaluate the predictive performance of Bayesian causal inference for human perceptual decisions in a spatial prediction task based on noisy audiovisual sequences with occasional changepoints. We elucidate the simplifying assumptions of a previously proposed reduced Bayesian observer model, and we compare it to an extensive set of models based on alternative simplification strategies. Model-free analyses revealed the hallmarks of Bayesian causal inference: participants seem to have integrated sensory evidence with prior beliefs to improve accuracy when prediction errors were small, and prior influence gradually decreased as prediction errors grew larger, signalling probable irrelevance of the prior due to a changepoint. Model comparison results further supported the hypotheses that participants computed probability-weighted averages over the causal options (noise or changepoint) and that they iteratively summarized their beliefs while accounting for causal uncertainty akin to the reduced Bayesian observer model. However, we also found that participants' reliance on prior beliefs was systematically smaller than predicted by the model, and this was best explained by individually fitting lower-than-optimal parameters for the a-priori probability of prior relevance. We conclude that perceptual belief updating in volatile environments with stochastic noise is well described by a simplified model of consecutive Bayesian causal inference. Observers utilize priors flexibly to the extent that they are deemed relevant, though also conservatively with a lower tendency to bind than an ideal Bayesian observer.

Intra-arterial Deoxyribonuclease therapy improves stroke outcomes in aged mice
Background: Futile recanalization affects more than half of acute ischemic stroke (AIS) patients. Neutrophil extracellular traps (NETs) are a major factor of microvascular hypoperfusion after stroke. Deoxyribonuclease I (DNase) targeting NETs exhibited a neuroprotective effect in young mice with AIS. This study explored a novel direct intra-arterial administration of DNase therapy and its effect in aged mice with AIS. Method: AIS was induced in aged C57BL/6 mice followed by reperfusion and immediate, intra-arterial DNase administration via the internal carotid artery. Cerebral blood flow, neurological function, cerebral infarct volume, and NET markers were examined. Results: Direct intra-arterial DNase therapy significantly increased cerebral blood flow, reduced neurological deficit scores, increased the latency to fall in wire hang test, reduced cerebral infarct volume, and decreased neutrophil and NET count in both the parenchyma and micro vessels in aged mice with AIS compared with age-matched, vehicle controls. Conclusion: Our data is the first to demonstrate that successful, direct intra-arterial DNase therapy provides more efficient cerebral reperfusion and better outcomes after recanalization during the treatment of large vessel occlusion in aged mice. This study provides evidence for the potential clinical application of catheter delivered intra-arterial DNase therapy post-recanalization.

Ephrin-mediated dendrite-dendrite repulsion regulates compartment- specific targeting of dendrites in the central nervous system
Neurons often forms synaptic contacts at specific subcellular domains to differentially regulate the activity of target neurons. However, how dendrites are targeted to specific subcellular domains of axons is rarely studied. Here we use Drosophila mushroom body out neurons (MBONs) and local dopaminergic neurons (DANs) as a model system to study how dendrites and axons are targeted to specific subcellular domains (compartments) of mushroom body axonal lobes to form synaptic contacts. We found that Ephrin-mediated dendrite- dendrite repulsion between neighboring compartments restricts the projection of MBON dendrites to their specific compartments and prevents the formation of ectopic synaptic connections with DAN axons in neighboring compartments. Meanwhile, DAN neurons in a subset of compartments may also depend on their partner MBONs for projecting their axons to a specific compartment and cover the same territory as their partner MBON dendrites. Our work reveals that compartment-specific targeting of MBON dendrites and DAN axons is regulated in part by a combination of dendrite-dendrite repulsion between neighboring compartments and dendrite-axon interactions within the same compartment.

Soft biocompatible polymer optical fiber tapers for implantable neural devices
Optical fibers are between the most common implantable devices for delivering light in the nervous system for optogenetics and infrared neural stimulation applications. Tapered optical fibers, in particular, can offer homogeneous light delivery to a large volume and spatially resolved illumination compared to standard flat-cleaved fibers while being minimally invasive. However, the use of tapers for neural applications has up to now been limited to silica optical fibers, whose large Young's modulus can cause detrimental foreign body response in chronic settings. Here, we present the fabrication and optimization of tapered fiber implants based on polymer optical fibers (POFs). After numerically determining the optimal materials and taper geometry, we fabricated two types of POFs by thermal fiber drawing. The fabrication of the taper was achieved by chemical etching of the fibers, for which several solvents previously reported in literature have been tested. The influence of different parameters on the etching process and on the quality of the obtained tapers was also investigated. The large illumination volume of the produced high-quality taper-based implants was finally tested in vitro in a brain phantom.

Distinct roles of brain network flexibility in motor learning across age
Motor learning is a lifelong process, from infancy through old age. Acquiring new motor skills through repetitive practice requires adjusting motor output in response to sensory input and integrating them to facilitate learning. For this to occur, the central nervous system must flexibly predict and adapt to the dynamic interplay between sensory inputs and motor outputs. Although overall brain function changes with age, it remains unclear how neural flexibility evolves and influences motor learning ability with aging. To address this, we designed a motor learning paradigm involving both younger and older adults and quantitatively assessed neural flexibility from the perspective of functional brain networks, leveraging multichannel electroencephalography (EEG) in humans. Here we found age-related differences in motor learning properties, brain network flexibility, and their neural relationships. In younger adults, motor learning retention was associated with brain network flexibility during the preparatory period of the task. However, this association was not observed in older adults. Together, our findings establish that brain network flexibility plays a crucial role in acquiring and maintaining new motor skills in younger adults, but this relationship becomes less effective with age.

Somatomotor disconnection links sleep duration with socioeconomic context, screen time, cognition, and psychopathology
Background: Sleep is critical for healthy brain development and emotional wellbeing, especially during adolescence when sleep, behavior, and neurobiology are rapidly evolving. Theoretical reviews and empirical research have historically focused on how sleep influences mental health through its impact on higher-order brain systems. No studies have leveraged data-driven network neuroscience methods to uncover interpretable, brain-wide signatures of sleep duration in adolescence, their socio-environmental origins, or their consequences for cognition and mental health. Methods: Here, we implement graph theory and component-based predictive modeling to examine how a multimodal index of sleep duration is associated with intrinsic brain architecture in 3,173 youth (11-12 years) from the Adolescent Brain Cognitive DevelopmentSM Study. Results: We demonstrate that network integration/segregation exhibit a strong, generalizable multivariate association with sleep duration. We next identify a single component of brain architecture centered on a single network as the dominant contributor of this relationship. This component is characterized by increasing disconnection of a lower-order system - the somatomotor network - from other systems, with shorter sleep duration. Finally, greater somatomotor disconnection is associated with lower socioeconomic resources, longer screen times, reduced cognitive/academic performance, and elevated externalizing problems. Conclusions: These findings reveal a novel neural signature of shorter sleep in adolescence that is intertwined with environmental risk, cognition, and psychopathology. By robustly elucidating the key involvement of an understudied brain system in sleep, cognition, and psychopathology, this study can inform theoretical and translational research directions on sleep to promote neurobehavioral development and mental health during the adolescent transition.

Trading Place for Space: Increasing Location Resolution Reduces Contextual Capacity in Hippocampal Codes
Many animals learn cognitive maps of their environment - a simultaneous representation of context, experience, and position. Place cells in the hippocampus, named for their explicit encoding of position, are believed to be a neural substrate of these maps, with place cell "remapping" explaining how this system can represent different contexts. Briefly, place cells alter their firing properties, or "remap", in response to changes in experiential or sensory cues. Substantial sensory changes, produced, e.g., by moving between environments, cause large subpopulations of place cells to change their tuning entirely. While many studies have looked at the physiological basis of remapping, we lack explicit calculations of how the contextual capacity of the place cell system changes as a function of place field firing properties. Here, we propose a geometric approach to understanding population level activity of place cells. Using known firing field statistics, we investigate how changes to place cell firing properties affect the distances between representations of different environments within firing rate space. Using this approach, we find that the number of contexts storable by the hippocampus grows exponentially with the number of place cells, and calculate this exponent for environments of different sizes. We identify a fundamental trade-off between high resolution encoding of position and the number of storable contexts. This trade-off is tuned by place cell width, which might explain the change in firing field scale along the dorsal-ventral axis of the hippocampus. We demonstrate that clustering of place cells near likely points of confusion, such as boundaries, increases the contextual capacity of the place system within our framework and conclude by discussing how our geometric approach could be extended to include other cell types and abstract spaces.

A Nostalgia Brain-Music Interface for Enhancing Nostalgia, Well-Being, and Memory Vividness in Young and Elderly Individuals
Music-evoked nostalgia has the potential to assist in recalling autobiographical memories and enhancing well-being. However, nostalgic music preferences vary from person to person, presenting challenges for applying nostalgia-based music interventions in clinical settings, such as a non-pharmacological approach. To address these individual differences, we developed the Nostalgia Brain-Music Interface (N-BMI), a neurofeedback system that recommends nostalgic songs tailored to each individual. This system is based on prediction models of nostalgic feelings, developed by integrating subjective nostalgia ratings, acoustic features and in-ear electroencephalographic (EEG) data during song listening. To test the effects of N-BMI on nostalgic feelings, well-being, and memory recall, seventeen elderly and seventeen young participants took part in the study. The N-BMI was personalized for each individual, and songs were recommended under two conditions: the "nostalgia condition", where songs were selected to enhance nostalgic feelings, and the "control condition", to reduce nostalgic feelings. We found nostalgic feelings, well-being, and memory vividness were significantly higher after listening to the recommended songs in the nostalgia condition compared to the control condition in both groups. This indicates that the N-BMI enhanced nostalgic feelings, well-being, and memory recall across both groups. The N-BMI paves the way for innovative therapeutic interventions, including non-pharmacological approaches.

Ictal-Related Chirp as a Biomarker for Monitoring Seizure Progression
Despite being prevalent, the causes, mechanisms, and progression of epilepsy, a chronic neurological disorder with unprovoked seizures, are not well understood, complicating drug development for treatment. This study used a comprehensive mouse epilepsy kindling model dataset to investigate frequency modulation (chirp) as a potential indicator of distinct states of epilepsy (early evoked discharge, late evoked discharge, spontaneous recurrent seizure, and drug state). Employing time-frequency ridge extraction, chirp identification, and statistical testing, our analyses revealed that chirp patterns occur in the majority of ictal discharges (>81.6%), persisting across evoked and spontaneous seizures. While the focus was on hippocampal recordings, chirps were also detected in the piriform peripheral cortex. Significant frequency and duration changes in chirp patterns during the transition from early to late evoked ictal events suggest their potential as the screening tool for seizure progression. Additionally, detailed analyses illuminate the impact of Lorazepam, a GABA A enhancer, on chirp characteristics, providing insights into how increased inhibitory tone quantifiably influences excitatory-inhibitory balances during seizures.

Task-irrelevant features in working memory alter current visual processing
Higher-level cognition depends on visual working memory (VWM), the ability of our brain to maintain and manipulate internal representations of images that are no longer presented to us. An important question in this field is whether VWM is represented in a sensory or nonsensory manner. Progress has been made in understanding the features to be remembered, but the representational nature of the memory-irrelevant features is unclear. Here, we used a dual-task paradigm to investigate how and when the memory-irrelevant features interact with the concurrent visual information. In a series of experiments, participants were asked to perform a visual search task (Experiment 1) or a perceptual discrimination task (Experiments 2 and 3) involving a memory irrelevant feature while simultaneously holding the other feature for later retrieval. Experiment 1 showed that VWM biases the allocation of attention to color matching to the memory-irrelevant color. More importantly, the degree of VWM-biased attention decreased monotonically with decreasing feature similarity, and this behavioral monotonic gradient profile resembled the tuning curve of feature-selective neurons in the early visual cortex. Experiment 2 revealed that irrelevant features biased ongoing perception, as indicated by the shifted discrimination threshold. Experiment 3 further demonstrated that VWM-biased perception occurs only at short delays but not at prolonged delays. Our results suggest that the memory-irrelevant feature is represented as a sensory analog for a limited period of time in the visual areas where it was initially processed. Our results extend sensory recruitment theory to memory-irrelevant features in VWM.

Dynamic imbalances in cell-type specific striatal ensemble activity during visually guided locomotion.
Locomotion is continuously regulated by an animals position within an environment relative to goals. Direct and indirect pathway striatal output neurons (dSPNs and iSPNs) influence locomotion, but how their activity is naturally coordinated by changing environments is unknown. We found, in head-fixed mice, that the relative balance of dSPN and iSPN activity was dynamically modulated with respect to position within a visually-guided locomotor trajectory to retrieve reward. Imbalances were present within ensembles of position-tuned SPNs which were sensitive to the visual environment. Our results suggest a model in which competitive imbalances in striatal output are created by learned associations with sensory input to shape context dependent locomotion.

Aging increases the distinctiveness of emotional brain states across rumination, worry, and positive thinking
Emotional well-being improves with age, but how neural activity related to emotional brain states changes with aging remains unclear. This study examined individualized brain activation patterns for rumination, worry, and positive thinking to explore age-related variations in emotional state representation. Thirty-five participants (aged 18-64) recalled autobiographical events tied to these emotional states during fMRI scanning. Brain activity was analyzed using an individualized machine learning classifier. Results showed increased discriminability of rumination and worry with age, with older adults exhibiting heightened activation in cognitive control regions during rumination and reduced activation in the cingulate and temporoparietal junction during worry. No significant age-related changes were found for positive thinking, although increased discriminability between positive and negative states correlated with well-being (FDR < 0.05). These findings suggest that aging enhances cognitive control during rumination and reduces anxiety responses during worry, potentially contributing to improved emotional well-being in older adults.

Pup defence in lactating rats: The underlying neuropeptide signalling and their interactions in the nucleus accumbens shell
Maternal aggression is a core feature of rodent maternal behaviour to defend their offspring from potential threats and is modulated by corticotropin-releasing factor (CRF) and oxytocin (OXT) systems signalling. Here, we investigated the involvement of those neuropeptide systems in maternal aggression within the nucleus accumbens shell (NAcSh), a central region of the reward and maternal circuits. Infusion of CRF or Urocortin3 (CRF- receptor 2 agonist), as well as an OXT receptor antagonist, reduced maternal aggression, suggesting a role in pup defence. Furthermore, the effects of CRF infusion in the NAcSh continued beyond the maternal defence test (MDT), reducing nursing and increasing self- grooming. Corroborating the involvement of the stress system in maternal aggression, colocalization of CRF and cFos immunoreactive cells were increased in response to the MDT, regardless of pup presence. In addition, MDT exposure increased intra-NAc OXT release in lactating rats, which could be also triggered by local retrodialysis of CRF, but not Urocortin3. However, both ligands of the CRF system elicited dopamine (DA) release in different dynamics. Crh-r1 were predominantly expressed in the medial NAc on medium-sized spiny neurons (MSN), but also in the rostral part on GABAergic interneurons. Crh-r2 were mainly expressed in the rostral NAc and its expression on GABAergic interneurons increased towards the caudal pole. Lastly, we identified CRF-enriched projections to the NAcSh descending from the prefrontal cortex, the amygdala, and the paraventricular thalamus, among others. In conclusion, intra-NAcSh dampened CRF system activity and enhanced OXT system transmission are indispensable for successful pup defence. Any perturbations like increased CRF system signalling might activate compensatory mechanisms to ensure adequate maternal behaviour.

Resistance of E2F4DN to p38MAPK phosphorylation attenuates DNA damage-induced neuronal death via Cited2
E2F4, a transcription factor with a prominent role in cell homeostasis, can be phosphorylated by the stress kinase p38MAPK at the Thr248/Thr250 motif, while the Thr248Ala/Thr250Ala E2F4 mutant (E2F4DN) triggers multifactorial therapeutic effects in a murine model of Alzheimer's disease. We hypothesized that the mechanism of action of this therapy relays on the phosphorylation of the Thr248/Thr250 motif under stress conditions, which prevents the homeostatic function of E2F4, while exogenous E2F4DN expression can restore this function. To provide support to this hypothesis, we have focused on genotoxicity induced by camptothecin (CPT) in N2a neuroblastoma-derived neurons, as a paradigm of cell stress followed by cell death. Here we show that, in these cells, p38MAPK becomes activated 6 h after CPT treatment, followed by E2F4 phosphorylation in the Thr248/Thr250 motif. The effect of this phosphorylation in apoptosis was tested by overexpressing wild-type E2F4 (E2F4WT), its Thr248Glu/Thr250Glu phosphomimetic (E2F4CA) or E2F4DN in CPT-treated N2a neurons, followed by quantification of procaspase-3 cleavage. E2F1, which was used as a positive control, induced a statistically-significant increase of procaspase-3 cleavage 32 h after CPT treatment. This was mimicked by either E2F4WT or E2F4CA, while E2F4DN expression inhibited this effect through a Cited2-dependent mechanism. Pharmacological p38MAPK inhibition prevented cell death by E2F4WT but not by E2F4CA, confirming the requirement of E2F4 phosphorylation for cell death in these cells. We conclude that the phosphorylation of E2F4 facilitates the death of N2a neurons carrying DNA damage, while E2F4DN maintains the homeostatic function of E2F4 under stress conditions.

Quantification of the effect of hemodynamic occlusion in two-photon imaging
The last few years have seen an explosion in the number of tools available to measure neuronal activity using fluorescence imaging (Chen et al., 2013; Feng et al., 2019; Jing et al., 2019; Sun et al., 2018; Wan et al., 2021). When performed in vivo, these measurements are invariably contaminated by hemodynamic occlusion artifacts. In widefield calcium imaging, this problem is well recognized. For two-photon imaging, however, the effects of hemodynamic occlusion have only been sparsely characterized. Here we perform a quantification of hemodynamic occlusion effects using measurements of fluorescence changes observed with GFP expression using both widefield and two-photon imaging. We find that in many instances the magnitude of signal changes attributable to hemodynamic occlusion is comparable to that observed with activity sensors. Moreover, we find that hemodynamic occlusion effects were spatially heterogeneous, both over cortical regions and across cortical depth, and exhibited a complex relationship with behavior. Thus, hemodynamic occlusion is an important caveat to consider when analyzing and interpreting not just widefield but also two-photon imaging data.

An fMRI-based Approach for Measuring Contrast Sensitivity Across the Visual Field in Visual Cortex
Peripheral vision is crucial for daily activities and quality of life, yet traditional measures of visual function like visual acuity primarily assess central vision. Visual field tests can evaluate peripheral vision but require extended focus combined with precise fixation, often very challenging for patients with severe sight loss. Functional MRI (fMRI) with population receptive field (pRF) mapping offers a non-invasive way to map scotomas but is limited by its reliance on single contrast levels and the necessity of accurate fixation. We developed an fMRI-based approach to measure contrast sensitivity across the visual field without the need for precise fixation. By combining large-field stimulation with varying spatial frequencies and contrast levels with either pRF mapping or a retinotopic atlas based on anatomical landmarks, we modeled contrast sensitivity in the primary visual cortex (V1) over a large (40 deg) expanse of the visual field. In seven normal-sighted participants, we characterized differences in V1 cortical sensitivity across eccentricities and visual quadrants, finding reliable and reproducible patterns of sensitivity differences at individual and session levels. Additionally, our method effectively visualized cases of simulated and disease-linked sensitivity loss at the cortical level. Crucially, we demonstrated that these results could be largely recovered using a structure-based retinotopic atlas, eliminating the need for pRF mapping and precise fixation - although such an approach reduced sensitivity. This approach, integrating large-field stimulation with a retinotopic atlas, offers a promising tool for monitoring vision loss and recovery in patients with various visual impairments, addressing a significant challenge in current clinical assessments.

Transcranial Brain-Wide Functional Ultrasound and Ultrasound Localization Microscopy in Mice using Multilinear Probes
Functional ultrasound imaging (fUS) and ultrasound localization microscopy (ULM) are advanced ultrasound imaging modalities for assessing both functional and anatomical characteristics of the brain. However, the application of these techniques at a whole-brain scale has been limited by technological challenges. While conventional linear acoustic probes provide a narrow 2D field of view and matrix probes lack sufficient sensitivity for 3D transcranial fUS, multilinear probes have been developed to combine high sensitivity to blood flow with fast 3D acquisitions. In this study, we present a novel approach the combined implementation of transcranial whole-brain fUS and ULM in mice using a motorized multilinear probe. This technique provides high-resolution, non-invasive imaging of neurovascular dynamics across the entire brain. Our findings reveal a significant correlation between absolute cerebral blood volume ({Delta}CBV) increases and microbubble velocity, indicating vessel-level dependency of the evoked response. However, the lack of correlation with relative CBV (rCBV) suggests that fUS cannot distinguish functional responses alterations across different arterial vascular compartments. This methodology holds promise for advancing our understanding of neurovascular coupling and could be applied in brain disease diagnostics and therapeutic monitoring.

Slit regulates compartment-specific targeting of dendrites and axons in the Drosophila brain
Proper functioning of the nervous system requires precise neuronal connections at subcellular domains, which can be achieved by projection of axons or dendrites to subcellular domains of target neurons. Here we studied subcellular-specific targeting of dendrites and axons in the Drosophila mushroom body (MB), where mushroom body output neurons (MBONs) and local dopaminergic neurons (DAN) project their dendrites and axons, respectively, to specific compartments of MB axons. Through genetic ablation, we demonstrate that compartment-specific targeting of MBON dendrites and DAN axons involves mutual repulsion of MBON dendrites and/or DAN axons between neighboring compartments. We further show that Slit expressed in subset of DANs mediates such repulsion by acting through different Robo receptors in different neurons. Loss of Slit-mediated repulsion leads to projection of MBON dendrites and DAN axons into neighboring compartments, resulting formation of ectopic synaptic contacts between MBONs and DANs and changes in olfactory-associative learning. Together, our findings suggest that Slit-mediated repulsion controls compartment-specific targeting of MBON dendrites and DAN axons, which ensures precise connections between MBON dendrites and DAN axons and proper learning and memory formation.

Maladaptation of Memory Systems Impairs Dorsal CA1-Dependent Temporal Binding and Declarative Memory in The Cntnap2 Knockout Mouse Model of Autism
The CA1 region of the hippocampus plays a multifaceted role in cognitive functions related to temporal binding, spatial navigation, and social interactions. Growing evidence reports a role of the hippocampus in the pathophysiology of autism spectrum disorder, particularly in social interactions and cognitive domains. Yet, the mechanisms driving hippocampal-driven cognitive impairments remain poorly defined. Here, we characterized how dorsal CA1 dysfunction impacts the long term retention of temporally discontiguous events. We found that Cntnap2 knockout mice exhibit reduced temporal binding capabilities compared to controls, stemming from decreased dorsal CA1 activity during temporal gaps. We further demonstrate a deficit of the flexibility component of relational/declarative memory in Cntnap2 KO mice. This impairment was secondary to the use of a procedural learning strategy associated with the imbalance of memory systems, in favor of the activity of the frontal-striatal areas, instead of the hippocampus. This study offers deeper insights into how memory systems are mistuned in autism, opening new avenues for understanding and addressing atypical cognition in this condition.

Retrograde transport of neurotrophin receptor TrkB-FL induced by excitotoxicity regulates Golgi stability and is a target for stroke neuroprotection
Excitotoxicity, aberrant function of survival pathways dependent on brain-derived neurotrophic factor (BDNF) and disruption of the Golgi complex are shared pathological hallmarks of relevant chronic and acute neurological diseases, including stroke. However, precise interdependence among these mechanisms is not completely defined, a knowledge essential to develop neuroprotective strategies. For ischemic stroke, a leading cause of death, disability and dementia, promising results have been obtained by interfering excitotoxicity, major mechanism of neuronal death in the penumbra area surrounding the infarct. We are exploring neuroprotection by promotion of survival cascades dependent on BDNF binding to full-length tropomyosin-related kinase B (TrkB-FL) receptor, which become aberrant after excitotoxicity induction. We have previously developed a blood-brain barrier (BBB) permeable neuroprotective peptide (MTFL457) containing a TrkB-FL sequence which efficiently prevents receptor processing induced by excitotoxicity and preserves BDNF-dependent pathways in a model of ischemia, where it efficiently decreases infarct size and improves neurological outcome after stroke. In this work, using cellular and animal models, we demonstrate that excitotoxicity-induced TrkB-FL downregulation is secondary to receptor endocytosis, receptor interaction with endosomal protein hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), retrograde transport to the Golgi and disruption of this organelle. Interestingly, peptide MTFL457 efficiently interferes TrkB-FL/Hrs interaction and receptor trafficking, processes required for excitotoxic Golgi fragmentation and TrkB-FL cleavage, demonstrating a central role for TrkB-FL in the control of Golgi stability. These results also suggest the potential of peptide MTFL457 to preserve function of this organelle and of critical neuronal survival pathways in stroke and, probably, other neurodegenerative diseases associated to excitotoxicity.

SCAD Delivery Platform: A Novel Approach for Efficient CNS and Extrahepatic Oligonucleotide Therapeutics
Oligonucleotide therapeutics, including antisense oligonucleotides (ASOs) and duplex RNAs like siRNA, saRNA, and miRNA, hold immense potential for treating genetic and acquired diseases by modulating gene expression in a target-specific manner. However, effective delivery to extrahepatic tissues, particularly the central nervous system (CNS), remains a significant challenge. While GalNAc conjugation has enabled liver-specific delivery, leading to several approved siRNA drugs for hepatic targets, CNS delivery lags. ASOs, on the other hand, can self-deliver to the CNS when administered locally, as seen with nusinersen and tofersen. To address this disparity, we've developed the Smart Chemistry Aided Delivery (SCAD) platform which enables duplex RNA delivery by conjugating it to an accessory oligonucleotide (ACO), which acts as an aptamer to mediate protein binding and facilitate cellular uptake. Through extensive screening, we identified an optimal SCAD architecture that demonstrates enhanced cell-free protein binding and in vitro activity. In rodent models, local administration of SCAD-siRNA conjugates resulted in broad biodistribution throughout the CNS and sustained mRNA knockdown for over five months, with a favorable safety profile. The SCAD platform also exhibited efficient delivery to other tissues, including the eye, the lung and the joint. These features support its potential for broader clinical applications, as evidenced by an ongoing trial targeting amyotrophic lateral sclerosis (ALS) associated with mutations in the SOD1 gene. The modular design of SCAD allows it to easily adapt to any duplex RNA, making it a powerful tool for advancing oligonucleotide therapeutics.

Adaptive Gaze and Hand Coordination while Manipulating and Monitoring the Environment in Parallel
Research on eye-hand coordination has focused on action tasks performed in isolation. However, real world action tasks are often performed concurrently with perception tasks that compete for gaze. Here we examine how participants adapt their eye and hand movements when performing an object manipulation task, in which they repeatedly grasped a ball and inserted it into a slot, while simultaneously monitoring a text display to detect probabilistically occurring letter changes. We varied the visuomotor demands of the action task by having participants use either their fingertips or tweezers. We found that fixations allocated to the action task were exclusively directed to the ball and slot, and were more prevalent when using tweezers. The timing of ball and slot fixations were coupled in time with ball grasp and slot entry. On average, gaze shifted away from the landmarks ~400 ms before contact when using fingertips,allowing the use of peripheral vision to direct the hand, and around the contact time when using tweezers, further allowing central vision to guide the hand as it approached the ball or slot. We found that participants controlled the timing of their hand movements, as well as the timing and patterns (sequence of fixations) of their eye movements, to exploit the temporal regularities of the perception task, thereby lowering the probability that a letter change would occur during action task fixations. Our results illustrate that eye-hand coordination can be flexibly and intelligently adapted when simultaneously acting on and perceiving the environment.

A Surface-based deep learning approach for cortical shape analysis
Advances in deep learning hold promise for predicting clinical factors from human brain images. In this study, we applied a spherical harmonics-based convolutional neural network approach (SPHARM-Net) to MRI-derived brain shape metrics to predict age, sex, and Alzheimer's disease (AD) diagnosis. MRI-derived brain features included vertex-wise cortical curvature, convexity, thickness, and surface area. SPHARM-Net performs convolutions using the spherical harmonic transforms, eliminating the need to explicitly define neighborhood size, and achieving rotational equivariance. Sex classification and age regression were carried out in a large sample of healthy adults (UK Biobank; N=32,979), and AD classification performance was tested in a large, publicly available sample (ADNI; N=1,213). SPHARM-Net showed strong performance for sex classification (accuracy=0.91; balanced accuracy= 0.91; AUC=0.97), and age regression (average absolute error=2.97 years; R-squared=0.77; Pearson's coefficient=0.9). AD classification also performed well (accuracy=0.86; balanced accuracy=0.83; AUC=0.9). Our experiments demonstrate promising preliminary performance using the SPHARM-Net for two widely studied benchmarking tasks and for AD classification. Future work will include comparisons of shape-based methods and extending these analysis to more challenging tasks such as mood disorder classification.

Transcriptional profiling of the cortico-accumbal pathway reveals sex-specific alterations underlying stress susceptibility
Anxiety and depressive disorders, including major depressive disorder (MDD), affect millions of people every year, imposing significant socio-economic burdens. In this scenario, current treatments for MDD show limited efficacy, highlighting the need to better understand its molecular mechanisms. The medial prefrontal cortex (mPFC) has been identified as a critical brain region in MDD pathology, displaying altered activity and morphology. This study targets the mPFC-to-nucleus accumbens (NAc) pathway, which is implicated in the regulation of emotional behavior. We used a pathway-specific approach to uncover transcriptional profiles in mPFC neurons projecting to the NAc in stressed male and female mice. Using the RiboTag technique and RNA sequencing, we identified sex-specific gene expression changes, revealing potential roles in stress susceptibility. Differential expression and weighted gene co-expression network analyses revealed distinct transcriptional responses to chronic stress in males and females. Key findings include the identification of the X-linked lymphocyte-regulated 4B (Xlr4b) gene, within a highly relevant gene module, as a stress susceptibility driver in males. By experimentally overexpressing the Xlr4b gene, we characterized its crucial role in regulating neuronal firing and influencing arborization patterns to promote anxiety-like behavior in a sex-specific fashion. These findings suggest that chronic stress induces unique and shared transcriptional alterations in mPFC neurons projecting to the NAc. Some of these alterations change the morphological and functional properties of neuronal pathways ultimately contributing to the differential manifestation of anxiety-like and depressive-like behaviors in male and female mice.

Dual-site transcranial alternating current stimulation over the primary motor cortices increases interhemispheric inhibition and improves bimanual dexterity: A triple-blind, randomised, sham-controlled study
Concurrent application of transcranial alternating current stimulation (tACS) over distant cortical regions has been shown to modulate functional connectivity between stimulated regions; however, the precise mechanisms remain unclear. Here, we investigated how dual-site tACS (ds-tACS) applied over the bilateral primary motor cortices (M1s) modulates connectivity between M1s. Using a cross-over sham-controlled triple-blind within-subject design, 37 (27 female, age 18-37yrs) healthy participants received tACS (1.0mA, 20Hz) over the bilateral M1s for 20 min. Before and after tACS, functional connectivity between M1s was assessed using imaginary coherence (ImCoh) measured via resting-state electroencephalography (EEG) and interhemispheric inhibition (IHI) via dual-site transcranial magnetic stimulation (TMS) protocol. Additionally, manual dexterity was assessed using the Purdue pegboard task. While ImCoh remained unchanged after simulation, spectral power analysis showed a significant decrease in beta (20 Hz) power during the tACS session. ds-tACS but not sham strengthened IHI between the M1s and improved bimanual assembly performance. These results suggest that improvement in bimanual performance may be explained by modulation in M1-M1 IHI, rather than by coupling in the oscillatory activity. As functional connectivity underlies many clinical symptoms in neurological and psychiatric disorders, these findings are invaluable in developing non-invasive therapeutic interventions that target neural networks to alleviate symptoms.

Sensitivity of Cerebellar Reaching Ataxia to Kinematic and Dynamic Demands
Individuals with cerebellar ataxia often face significant challenges in controlling reaching, especially when multijoint movements are involved. This study investigated the effects of kinematic and dynamic demands on reaching movements by individuals with cerebellar ataxia and healthy controls using a virtual reality task. Participants reached to target locations designed to elicit a range of coordination strategies between shoulder and elbow joint movements. Results showed that the cerebellar group exhibited greater trajectory curvature and variability in hand paths compared to controls, with pronounced deficits in the initial hand movement direction. Kinematic simulations indicated that early hand movement errors were sensitive to the required onset times and rates of joint movements and were most impaired when opposite direction joint movements were required (e.g., elbow extension with shoulder flexion). This highlights significant disruptions in motion planning and feedforward control in the cerebellar group. Dynamic analysis showed that cerebellar participants' movements were more impaired in reaching directions where interaction torques normally assist the desired elbow and shoulder movements, which required them to rely more on muscle torques to move. These reach directions were also those that required opposite direction joint movements. Overall, our data suggest that reaching deficits in cerebellar ataxia result from 1) the early-phase motion planning deficits that worsen with tight timing requirements and 2) the inability to compensate for interaction torques, particularly when they assist the intended movement.

Dual transcranial electromagnetic stimulation of the precuneus-hippocampus network boosts human long-term memory
Non-invasive brain stimulation techniques have the potential to improve memory functions. However, the results so far have been relatively modest and time-consuming. Here, we implemented a novel 3-minute combination of personalized repetitive transcranial magnetic stimulation (intermittent theta burst-iTBS) coupled with simultaneous application of gamma transcranial alternating current stimulation ({gamma}tACS) over the precuneus, a brain area connected with the hippocampus, to modulate long term memory in healthy subjects. Only dual electromagnetic stimulation of the precuneus produced a consistent increase in long-term associative memory as compared to iTBS alone and sham conditions in a sample of healthy volunteers. The effects were replicated in another independent sample, in which the increased associative memory was retained for up to one week. Moreover, dual stimulation increased gamma oscillations and precuneus-hippocampus functional connectivity through the white matter tracts linking the precuneus with the temporal lobe. These findings show that dual stimulation may lead neuronal assemblies in a state favorable to enhance long-term plasticity and identify the precuneus as a key brain area involved in memory formation. Personalized dual electromagnetic stimulation of the precuneus-hippocampus network may represent a new powerful approach for enhancing memory functions in several healthy and clinical conditions.

A Novel Early Onset Spinocerebellar Ataxia 13 BAC Mouse Model with Cerebellar Hypoplasia, Tremor, and Ataxic Gait
Spinocerebellar ataxia 13 (SCA13) is an autosomal dominant neurological disorder caused by mutations in KCNC3. Our previous studies revealed that KCNC3 mutation R423H results in an early-onset form of SCA13. Previous biological models of SCA13 include zebrafish and Drosophila but no mammalian systems. More recently, mouse models with KCNC3 mutations presented behavioral abnormalities but without obvious pathological changes in the cerebellum, a hallmark of patients with SCA13. Here, we present a novel transgenic mouse model by bacterial artificial chromosome (BAC) recombineering to express the full-length mouse Kcnc3 expressing the R424H mutation. This BAC-R424H mice exhibited behavioral and pathological changes mimicking the clinical phenotype of the disease. The BAC-R424H mice (homologous to R423H in human) developed early onset clinical symptoms with aberrant gait, tremor, and cerebellar hypoplasia/atrophy. Histopathological analysis of the cerebellum in BAC-R424H mice showed progressive Purkinje cell loss and thinning of the molecular cell layer. Additionally, Purkinje cells of BAC-R424H mice showed significantly lower spontaneous firing frequency with a corresponding increase in inter-spike interval compared to that of wild-type mice. Our SCA13 transgenic mice recapitulate both neuropathological and behavioral changes manifested in human SCA13 R423H patients and provide an advantageous approach to understanding the role of voltage-gated potassium channel in cerebellar morphogenesis and function. This mammalian in vivo model will lead to further understanding of the R423H allelic form of SCA13 from the molecular to the behavioral level and serve as a platform for testing potential therapeutic compounds.

Linking Pre- and Perinatal Risk Factors to a Multivariate Fusion of Child Cortical Structure
Pre- and perinatal factors such as maternal pregnancy and child birth complications affect child brain development, emphasizing the importance of early life exposures. While most previous studies have focused on a few variables in isolation, here, we investigated associations between a broad range of pregnancy- and birth-related variables and multivariate cortical brain MRI features. Our sample consisted of 8,396 children aged 8.9 to 11.1 years from the ABCD Study. Through multiple correspondence analysis and factor analysis of mixed data, we distilled numerous pre- and perinatal variables into four overarching dimensions; maternal pregnancy complications, maternal substance use, compromised fetal growth, and newborn birth complications. Vertex-wise measures of cortical thickness, surface area, and curvature were fused using linked independent component analysis. Linear mixed effects models showed that maternal pregnancy complications and compromised fetal growth, including low birth weight, being born preterm, or as a twin, were associated with smaller global surface area. Additionally, compromised fetal growth was associated with two regional patterns reflecting a complex combination of 1) smaller occipital, inferior frontal and insular cortex, larger fronto-temporal cortex, thinner pre- and post-central cortex, and thicker inferior frontal and insular cortex, and 2) smaller and thicker occipital and temporal lobe cortex, and larger and thinner insular cortex. In contrast, maternal substance use and newborn birth complications showed no associations with child cortical structure. By employing a multifactorial and multivariate morphometric fusion approach, we connected complications during pregnancy and fetal growth to global surface area and specific regional signatures across child cortical MRI features.