Venue: BBS
Mélie Talaron
Team: Decision and Adptation – INCIA
Supervisors: Etienne Coutureau et Nathan Holmes (The University of New South Wales)
Title
How does the brain integrate sensory and emotional memories? A study of the role of the hippocampus in sensory preconditioning in rats
Abstract
Animals and humans adapt to their environments by learning to predict motivationally significant events such as the presence of food or danger. These predictions are often based on direct experience of the contingencies between different stimuli and events (e.g., a sound followed by the attack of a predator) but can also be generated in the absence of such experience. For example, by linking the sensory and emotional elements of distinct memories, we can generate novel inferences about stimuli that have only ever been experienced as innocuous. This type of inference has implications for how memories are encoded and stored in the brain; and raises the question of how they are integrated to generate adaptive behavior. The encoding and integration of associative memories are known to be hippocampus-dependent. Yet, the differential contributions of dorsal versus ventral hippocampus and their connectivity in these processes remains unclear. This thesis combines behavioral paradigms, pharmacological inactivations, fiber photometry recordings, and chemogenetic manipulations to investigate the role of dorsal and ventral hippocampus in the encoding and integration of sensory and emotional memories in rats. In the first set of experiments, we establish auditory-visual sensory preconditioning and show that integration operates via mediated learning: rats retrieve past information at the time of conditioning to form new associations between stimuli. In a second line of work, we use pharmacological inactivation to investigate the causal role of dorsal and ventral hippocampus in the different stages of sensory preconditioning. We show that ventral, but not dorsal, hippocampus is required to form innocuous stimulus-stimulus associations, and that both subregions are necessary for mediated learning. Critically, we identify the signature of successful mediated learning by evidencing higher dorso-ventral hippocampus connectivity during stimulus presentations. We show that this connection is part of a broader network supporting mediated learning, which includes the perirhinal cortex. Finally, using chemogenetic manipulation in a gustatory sensory preconditioning protocol, we demonstrate that the hippocampus is also critical to encode and integrate memories even when stimuli are unimodal. This work highlights the differential contributions of dorsal and ventral hippocampus in animals’ ability to infer outcomes in the absence of direct experience when facing novel situations.
Keywords: sensory preconditioning, hippocampus, rat, fear conditioning, conditioned taste aversion
Jury
M. JOHANSEN Joshua, Professor, Irvine University of California, Rapporteur
Mme DOYERE Valérie, Directrice de recherche, Institut des Neurosciences Paris-Saclay, Rapporteure
Mme BONARDI Charlotte, Senior Lecturer, University of Nottingham, Examinatrice
Mme ROUX Lisa, Directrice de recherche, Université de Bordeaux, Examinatrice
M. COUTUREAU Etienne, Directeur de recherche, Université de Bordeaux, Directeur de these
M. HOLMES Nathan, Associate Professor, The University of New South Wales, Co-directeur de these