Biology

Dr. Alan Carleton
University of Geneva

Sensory information is translated into ensemble representations by various populations of projection neurons in brain circuits. How neural codes are implemented in cell assemblies and how plasticity might affect population codes are still not fully understood. We have studied these questions in the mouse olfactory system. In mammals, odorant molecules are recognized by odorant receptors expressed at the surface of olfactory sensory neurons (OSNs) in the nasal epithelium. OSNs express only one type of receptor gene and their axons converge in a receptor-specific manner onto glomeruli in the main olfactory bulb (OB). In glomeruli, OB output neurons receive olfactory inputs from sensory neurons in common glomeruli, and in turn send output projections to distinct cortical regions of the brain. These output neurons are also strongly modulated by different populations of inhibitory interneurons. We shall see how odors activate complex spatio-temporal patterns of glomeruli and consequently activate dynamic ensembles of projection neurons. We will present some computation performed in the olfactory circuit and we shall see how experience may modify odor coding.