par, , - 28 novembre 2012
Coding and memory in olfaction
Coding of an odorant mixture
Odors are mostly mixture of several tens of hundreds molecules. As a fundamental rule, the olfactory system processes odors from both a synthetic and an analytic point of view. Thus, by appreciating the global quality of an odor mixture, the olfactory system works in configural coding mode, whereas by identifying its different components, it works in elemental coding mode. The state of the art led us to think that these two coding modes could be evidenced at the two first levels of the system, the olfactory receptor neurons (ORN) and olfactory bulb (OB). Indeed, faced with natural complex odors, single ORNs simultaneously integrate several molecular signals and give rise to responses which are never the simple addition of their responses to single molecules. So, molecular interactions at binding/transduction levels could be mutually suppressive or synergistic. By generalizing these results, the simultaneous action of the numerous molecules forming a natural odor should result in refining the active neuronal assembly which encodes a specific odor by reducing the overlap, via the interplay of suppression and synergy. This game may result in a peripheral code which cannot be predicted from the codes of individual components and which may contain determining keys for the configural and elemental coding modes. Indeed, the peripheral interactions between components reliably reflect the final perception of odor mixtures. We propose to disentangle the issue of configural vs elemental coding mode by deciphering the relation between peripheral cellular coding, bulbar spatial patterns and behavioral response to an odorant mixture.
Project 1 : Cellular approach of mixture coding : How the combinations of active ORN are built in response to single molecules and mixtures ? (Patricia Viret, Barbara Ferry, Nicola Kuczewski).
Project 2 : Relation between OB spatial map and discrimination of odorant mixtures in the behaving animal (Philippe Litaudon, Patricia Viret, Barbara Ferry).