Thalamocortical control of voluntary actions – THALACOR

Surviving in dynamic environments requires to arbitrate between the exploration of new options to gain more information or to exploit already known ones to secure a gain. The control of these voluntary actions relies on a highly distributed cortical-subcortical circuits among which secondary motor regions (M2) now emerge as critical integrative nodes. In THALACOR, we propose to examine the role of thalamocortical circuits constituted by connections between M2 and two key thalamic nuclei - the mediodorsal (MD) and the ventral anterior/ventral lateral thalamic (VAVL) nuclei - in the ability to decide between exploration or exploitation actions. We hypothesize that thalamocortical projections to M2 can differentially support exploration (MD-M2) and exploitation (VAVL-M2) actions based on our preliminary evidence that (i) projections from MD and VAVL converge onto specific M2 sites and that (ii) interfering with M2 or MD functions selectively disrupts exploration in bandit tasks aimed at capturing the exploration-exploitation trade-off. To capitalize on this initial dataset, we have built a 3-partners Bordeaux Neurocampus consortium with complementary expertise. We will first examine the fine architecture of the M2-MD/VAVL circuits with advanced neuroanatomy techniques (Mathieu Wolff, Coordinator-Partner 1, INCIA; Frédéric Gambino, Partner 2, IINS). We will then examine the functional connectivity between M2 and thalamic regions through multi-site electrophysiology as rats switch from exploitation to exploration both in a freely-moving (Partner 1; Lisa Roux, Partner 3, IINS) and a head-fixed variant of the bandit task to access axonal resolution via 2 photon microscopy (Partner 2). Finally, we will test the causal role of thalamocortical projections at the behavioral level by selectively suppressing MD-M2 or VAVL-M2 projections. We hope to reveal the neural underpinnings of voluntary actions, which may highlight the functional principles at play within these neural circuits as they are affected in multiple psychiatric conditions.