Influence de l'inhibition synaptique sur le codage de l'information par les cellules mitrales du bulbe olfactif

Abstract : The olfactory bulb is mainly composed of excitatory cells, called mitral cells, interconnected via local inhibitory neurons, called granule cells. The analysis of electrophysiological data, recorded in vitro from rat olfactory bulb slices, shows that mitral cell firing is phase-locked to the fast local field potential oscillation. This phase-locking is largely reduced when the inhibitory synaptic conductance is pharmacologically blocked, hence highlighting the important role of synaptic inhibition. We find that the inhibitory conductance fluctuations are correlated to the local field potential oscillations. A relationship between the received inhibition and the phase of mitral action potentials is also revealed. The probability to fire a phase-locked action potential increases if the neuron receives a large number of inhibitory synaptic events, and if these events are themselves phase-locked. Results from the previous analysis are used to design a computational model of the olfactory bulb in order to explore the encoding capacity of the mitral-granule interplay. It appears likely that mitral cells encode information in precise spike timings rather than in firing rates. We therefore study analytically the influence of the number and the temporal dispersion of the received inhibitory synaptic events on the spike timing precision of mitral cells. Our study concludes that spike timing precision requires a strong synaptic coupling between mitral and granule cells. Lastly, our olfactory bulb model is applied to the recognition of odours by using an array of artificial gas sensors.
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Maxime Ambard. Influence de l'inhibition synaptique sur le codage de l'information par les cellules mitrales du bulbe olfactif. Autre [cs.OH]. Université Henri Poincaré - Nancy 1, 2009. Français. ⟨NNT : 2009NAN10036⟩. ⟨tel-01748469⟩

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