Venue: BBS
Defense in french
Hadrien Plat
Team: DECAD
INCIA
Supervisor: Etienne Coutureau
Title
Apprendre à décider: une perspective neurocognitive chez le Rat. Le rôle de la noradrénaline préfrontale chez le rat dans le comportement adaptatif
Learning to decide: a neurocognitive perspective in rats. The role of rat prefrontal noradrenaline in adaptive behavior
Summary
Every day, organisms adapt their choices to a changing environment, relying on the ability to learn which actions lead to valuable outcomes and to revise these predictions when circumstances shift. Such adaptive decision-making is central to survival and is thought to depend on prefrontal circuits and their modulation by neuromodulators such as dopamine, noradrenaline or serotonin. Yet, the precise role of noradrenergic transmission in prefrontal subregions remains unclear. This thesis combines behavioural paradigms, circuit manipulations, fiber photometry recordings, and computational modelling to investigate how noradrenergic inputs to the medial prefrontal cortex (mPFC) and the orbitofrontal cortex (OFC) shape flexible learning. In the first set of experiments, we used a Pavlovian contingency degradation paradigm to probe stimulus–outcome updating. We show that noradrenergic transmission in the mPFC is necessary for adapting to changes in predictive contingencies, complementing its well-established involvement in instrumental contingency degradation that underpins goal-directed behaviour. In a second line of work, we used a reversal learning paradigm, where outdated associations must be abandoned and replaced with new ones. Here, we demonstrate that stronger noradrenaline responses in the OFC predict better individual performance, and we confirmed the causal role of this signal by showing that chemogenetic and optogenetic silencing of LC→OFC projections slowed reversal learning. Finally, using a probabilistic reversal learning task, we combined computational modeling, photometry recordings, and chemogenetic manipulations. We show that rat behavior is best explained by a metareinforcement learning model with volatility-dependent learning rates, that orbitofrontal noradrenaline seems to track these volatility estimates, and that silencing LC→OFC projections selectively slows adaptive adjustments, mimicking model lesions of volatility signaling. Taken together, these findings provide converging evidence that noradrenaline contributes in anatomically specific ways to flexible behavior. While NA in the mPFC is required for detecting and adapting to changes in the causal relationship between stimuli and their outcomes, NA in the OFC enables reversal and volatility-dependent adjustments of learning. This work highlights the complementary functions of prefrontal noradrenaline in ensuring that behavior remains both stable and adaptable in uncertain environments.
Jury
Mme DOYERE Valérie DR, CNRS, Université Paris-Saclay Rapporteure
M. GIRARD Benoit DR, CNRS, Université de la Sorbonne Rapporteur
Mme KOEHL Muriel DR, CNRS, Université de Bordeaux Examinatrice
M. PROCYK Emmanuel DR, CNRS, Université de Lyon Examinateur
M. COUTUREAU Etienne DR, CNRS, Université de Bordeaux Directeur de thèse