Biology subjects

Dard, R.

Publications and source records attributed to Dard, R..

3 recordsLinked to original sources

bioRxiv2026

Rapid cortical reorganization tracks goal-directed sensorimotor learning in real time

Sensorimotor associations are typically thought to require days of training to consolidate in sensory cortex, yet adaptive behavior can emerge within minutes. Here, we developed a barrel cortex-dependent whisker-based detection task in which mice learned to associate a novel tactile whisker stimulus with reward within a single behavioral session. Longitudinal two-photon calcium imaging of layer 2/3 barrel cortex neurons revealed that reward-driven learning rapidly reorganized the neuronal representation of the whisker deflection within a single session. Population decoding tracked this transition trial-by-trial during learning with neuronal trajectories mirroring behavior. Critically, neurons that gained stimulus responsiveness across training preferentially took part in spontaneous reactivation events during learning, suggesting that online reactivations could act as a potential upstream selection mechanism. Our results suggest that reward-based learning evokes rapid sensory cortical reorganization on the timescale of minutes, which could be mediated by a concurrent reactivation-based mechanism driving plasticity.

neuroscience↗

bioRxiv2025

Retrosplenial cortex enables context-dependent goal-directed sensorimotor transformation

The ability to dynamically adjust a behavioral response to a stimulus depending on context is of critical importance for animals. To investigate the neural basis supporting context-dependent sensory processing we developed a behavioral task in which mice changed their response to a single whisker deflection according to a continuously present contextual cue. Through unbiased optogenetic inactivation mapping, we found that neuronal activity in sensory and motor cortices contributed to task execution and, interestingly, we uncovered an unexpected role of retrosplenial cortex for contextual integration. Widefield calcium imaging revealed that retrosplenial cortex was the first dorsal cortical area to show context discrimination in response to whisker stimulation, followed by whisker motor cortex. Finally, we combined optogenetic inactivation with calcium imaging to define causal context-dependent changes in sensorimotor processing. Our cortex-wide mapping experiments thus begin to define key cortical nodes for context-dependent sensorimotor transformation and highlight an important contribution of retrosplenial cortex.

neuroscience↗

bioRxiv2023

Functional networks of inhibitory neurons orchestrate synchrony in the hippocampus

Inhibitory interneurons are pivotal components of cortical circuits. Beyond providing inhibition, they have been proposed to coordinate the firing of excitatory neurons within cell assemblies. While the roles of specific interneuron subtypes have been extensively studied, their influence on pyramidal cell synchrony in vivo remains elusive. Employing an all-optical approach, we simultaneously recorded hippocampal interneurons and pyramidal cells and probed the network influence of individual interneurons using optogenetics. We demonstrate that CA1 interneurons form a functionally interconnected network that promotes synchrony through disinhibition during awake immobility, while preserving endogenous cell assemblies. Our network model underscores the importance of both cell assemblies and dense, unspecific interneuron connectivity in explaining our experimental findings, suggesting that interneurons may operate not only via division of labor but also through concerted activity.

neuroscience↗