Role and connectivity of adult-born neurons in the olfactory bulb ; Rôle et connectivité des néo-neurones formés à l’âge adulte dans le bulbe olfactif

Olfaction is an important sensory modality in rodents. During odor-dependent learning, a positive value is commonly assigned to an odorant, and multiple forms of plasticity are involved when such odor–reward associations are formed. In the olfactory bulb, one of the mechanisms underlying plasticity consists in recruiting new neurons daily throughout life. The aim of this thesis was to determine the specific properties of these adult-born neurons, structurally and functionally. In a first study, we demonstrated that exposure to reward-associated odors specifically increases activity of adult-born neurons. Moreover, adult-born neuron activation during rewarded odor presentation heightens discrimination learning and enhances the ability to update the odor value during reversal association. Together, these results show the specific involvement of adult-born neurons in odor-reward association. In a second study, we investigated whether this functional role could result from a particular connectivity. We used a retrograde tracing technique to label the presynaptic partners of adult-born granule cells. Thus, we showed that centrifugal fibers contacting the adult-born granule cells are more numerous than those contacting their counterparts born during development. Collectively, these results demonstrate that adult neurogenesis endows the olfactory system with the capacity to facilitate associative learning, probably due to a unique connectivity. ; L’olfaction est un sens essentiel chez les rongeurs. Lors d’un apprentissage olfactif, des valeurs peuvent être attribuées aux odeurs ; de multiples formes de plasticité sont impliquées pour permettre cet apprentissage. Dans le bulbe olfactif, des nouveaux neurones, majoritairement des cellules en grain, sont produits chaque jour à l’âge adulte. Le but de cette thèse a été de déterminer les propriétés spécifiques de ces néo-neurones adultes, tant d’un point de vue structural que fonctionnel. Dans une première étude, nous avons montré que l’exposition aux odeurs associées à une ...