Implication du cervelet dans les circuits sensorimoteurs corticaux de contrôle du mouvement

L'acquisition d'information sensorielle et le contrôle moteur par l'organisme s'appuient l'un comme l'autre sur l'intégration sensori-motrice. En effet, l'interprétation des stimulis sensoriels nécessite généralement la connaissance des mouvements en cours, ce qui est particulièrement critique lors de l'exploration active de l'environnement, et réciproquement, l'information sensorielle est indispensable à la programmation, à la réalisation et à l'optimisation des mouvements. Malgré ce rôle clef dans les deux grandes fonctions neurophysiologiques que sont le contrôle moteur et l'analyse de l'information sensorielle, le substrat anatomo-fonctionnel de cette intégration reste encore mal décrit. Au cours de ma thèse, j'ai étudié tant l'organisation fine des voies sensorielles qui semble indiquer une forte ségrégation des flux d'information que les bases anatomiques et fonctionnelles qui pourraient sous-tendre l'intégration sensori-motrice notamment dans le cervelet.Sensory data acquisition and motor control both use sensori-motor integration. Indeed, interpretation of sensory stimuly needs to take into account ongoing movements. This is critical wduring active exploration of the environment. Reciprocally, sensory information is essential to plan, execute, and optimize movements. Sensori-motor integration has a crucial role in two major neurophysiological functions, motor control and sensory perception, but its anatomo-functional basis are still not well described. During my PhD thesis, I studied the fine organization of a sensory pathway, indicating a strong segregation of information streams as well as the anatomical and functional basis that could underlie sensori-motor integration, especially in the cerebellum.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Self-propulsion of inverse Leidenfrost drops on a cryogenic bath

International audienceWhen deposited on a hot bath, volatile drops are observed to stay in levitation: the so-called Leidenfrost effect. Here, we discuss drop dynamics in an inverse Leidenfrost situation where room-temperature drops are deposited on a liquid-nitrogen pool and levitate on a vapor film generated by evaporation of the bath. In the seconds following deposition, we observe that the droplets start to glide on the bath along a straight path, only disrupted by elastic bouncing close to the edges of the container. Initially at rest, these self-propelled drops accelerate within a few seconds and reach velocities on the order of a few centimeters per second before slowing down on a longer time scale. They remain self-propelled as long as they are sitting on the bath, even after freezing and cooling down to liquid-nitrogen temperature. We experimentally investigate the parameters that affect liquid motion and propose a model, based on the experimentally and numerically observed (stable) symmetry breaking within the vapor film that supports the drop. When the film thickness and the cooling dynamics of the drops are also modeled, the variations of the drop velocities can be accurately reproduced

Early selection of task-relevant features through population gating.

Brains can gracefully weed out irrelevant stimuli to guide behavior. This feat is believed to rely on a progressive selection of task-relevant stimuli across the cortical hierarchy, but the specific across-area interactions enabling stimulus selection are still unclear. Here, we propose that population gating, occurring within primary auditory cortex (A1) but controlled by top-down inputs from prelimbic region of medial prefrontal cortex (mPFC), can support across-area stimulus selection. Examining single-unit activity recorded while rats performed an auditory context-dependent task, we found that A1 encoded relevant and irrelevant stimuli along a common dimension of its neural space. Yet, the relevant stimulus encoding was enhanced along an extra dimension. In turn, mPFC encoded only the stimulus relevant to the ongoing context. To identify candidate mechanisms for stimulus selection within A1, we reverse-engineered low-rank RNNs trained on a similar task. Our analyses predicted that two context-modulated neural populations gated their preferred stimulus in opposite contexts, which we confirmed in further analyses of A1. Finally, we show in a two-region RNN how population gating within A1 could be controlled by top-down inputs from PFC, enabling flexible across-area communication despite fixed inter-areal connectivity

Whole-Brain Calcium Imaging during Physiological Vestibular Stimulation in Larval Zebrafish

International audienceThe vestibular apparatus provides animals with postural and movement-related information that is essential to adequately execute numerous sensorimotor tasks. In order to activate this sensory system in a physiological manner, one needs to macroscopically rotate or translate the animal’s head, which in turn renders simultaneous neural recordings highly challenging. Here we report on a novel miniaturized, light-sheet microscope that can be dynamically co-rotated with a head-restrained zebrafish larva, enabling controlled vestibular stimulation. The mechanical rigidity of the microscope allows one to perform whole-brain functional imaging with state-of-the-art resolution and signal-to-noise ratio while imposing up to 25° in angular position and 6,000°/s2 in rotational acceleration. We illustrate the potential of this novel setup by producing the first whole-brain response maps to sinusoidal and stepwise vestibular stimulation. The responsive population spans multiple brain areas and displays bilateral symmetry, and its organization is highly stereotypic across individuals. Using Fourier and regression analysis, we identified three major functional clusters that exhibit well-defined phasic and tonic response patterns to vestibular stimulation. Our rotatable light-sheet microscope provides a unique tool for systematically studying vestibular processing in the vertebrate brain and extends the potential of virtual-reality systems to explore complex multisensory and motor integration during simulated 3D navigation