Dissertation Defense - Thibaut Pardo

“The Role of Food Memories on Feeding Behavior”

Dr. Monica Dus, Chair

ABSTRACT: The circuit and cellular mechanisms that allow us to effectively interact and navigate our food environment are still elusive. These interactions depend on our ability to form associations between sensory information, such as olfactory, visual or taste, and the rewarding properties of food. Therefore, how our brain processes this rewarding information will impact food intake. Our food environment is mostly composed of foods high in sugars, which have been shown to change the rewarding and motivational properties of sugar as well as lead to obesity and overeating. Additionally, these changes are correlated with dysregulated dopaminergic system in mammals and humans. Therefore, our objective is to establish a causal relationship between the mechanisms controlling reward-motivated learning and overeating that are disrupted on a sugar diet (SD). Thus, we hypothesized that a SD decreases dopamine signaling to impair reward-motivated learning, promoting overeating and obesity. Using behavioral assays, in vivo 2-photon imaging and metabolic measurements, our results suggest that a subset of glutamatergic Mushroom Body Output Neurons regulate feeding behavior through learning and memory activity, and that a SD disrupts this mechanism through changes in dopamine neuromodulation. Together, my experiments have uncovered a novel circuit and cellular mechanisms through which the food environment promotes overconsumption and weight gain by affecting reward-motivated learning.