par- 27 janvier 2014
Bureau : 105
Coding of olfactory stimuli in the different stages of the system
For many years now, my main research interests have been the fundamental principles governing the olfactory code at different steps of the olfactory system. Since the twenties, the story shifted from the monomolecular odorantw to the multi-molecular odorants in mixture.
Indeed, real olfactory stimuli are mostly mixture of several tens of hundreds molecules. As a fundamental rule, the olfactory system processes the mixtures of volatile odorant molecules found in the environment from both a synthetic and an analytic point of view1. Thus, by appreciating the global quality of an odor mixture, the olfactory system works in configural coding mode, whereas by analyzing the different components of a mixture, it works in elemental coding mode2. The state of the art led us to think that these two coding modes could be evidenced at the olfactory receptor and mitral cell levels.
Peripheral approach of mixture coding :(In collaboration with Nicola Kuczewski)
Our main aim is to understand how the combinations of active ORN are built in response to single molecules and mixtures ?
The functional properties of ORNs will be investigated by using two preparations : in vitro intact explants of mucosa3 and in vivo mucosa4. By calcium imaging, we aimed to study how the combinations of active ORN are built in response to single molecules and mixtures in vitro (on mucosa explants) and in vivo (2-photon observation). To our knowledge, this should provide totally original data. Furthermore, we will go on our classic in vivo experiments which consist in unitary ORN and EOG recordings in anaesthetized freely breathing rats.
Olfactory bulb (OB) network approach of mixture coding : (in collaboration with Philippe Litaudon)
What happens to the peripheral olfactory code at the olfactory bulb level, in vigil animal ?
This questions aims on the one hand, to tackle the peripheral information transfer rules and on the other hand, to estimate the OB code in vigil animals by optical imaging. The latter point requests to develop the vigil rat model. However, in the view of available data on olfactory coding and of evidences that anesthesia drastically affects the olfactory code5, such a development appears indispensable. This question will likely lead us to re-examine, in lights of the available data in anesthetized animals, what is the real part of glomerular spatial coding in the code.
Behavioral approach of mixture coding : (in collaboration with barbara Ferry)
Since the fundamental olfactory cues can be defined through synergy, overshadowing, configural and elemental processing, how far does the peripheral processing reflect these different modes ?
This part aims at establishing behavioral and cognitive evidences of odorant interaction in mixture as they could be predict from cellular or OB network response indices. The behavioral approaches will be done in rats that will be submitted to associative tasks using reward as the unconditioned stimulus tasks, targeting the animal ability to detect and discriminate single odorants and mixtures of interest6. The data will be read in term of perceptual properties of binary mixtures of odorants of interest (suspected on the basis of cellular results) to trigger distinct sensory effects such as synergy, masking, compromise, subtraction, elemental or configural processing, or perceptual dominance.
1- Livermore, A. and Laing, D.G (1998). The influence of chemical complexity on the perception of multicomponent odour mixtures. Percept Psychophys. 98 ; 60:650-61.
2- Kay, L.M., Lowry, C.A. and Jacobs, H.A. (2003) Receptor contributions to configural and elemental odour mixture perception, Behav. Neurosci., 117, 1108-114.
3- Savigner A, Duchamp-Viret P, Grosmaitre X, Chaput M, Garcia S, Ma M, Palouzier-Paulignan B. (2009) Modulation of spontaneous and odorant-evoked activity, of rat olfactory sensory neurons, by two anorectic peptides, insulin and leptin. J. Neurophysiol., 101(6):2898-906.
4-Patricia Duchamp-Viret, - Duchamp-Viret, P., Chaput, M. and Duchamp, A. Odor response properties of rat olfactory receptor neurons, Science, 1999, 284, 2171-2174.
5-Patricia Duchamp-Viret, - Duchamp-Viret, P., Chaput, M. and Duchamp, A. Odor response properties of rat olfactory receptor neurons, Science, 1999, 284, 2171-2174.
6-Kimberly J. Grossman,Atul K. Mallik,Jessica Ross,Leslie M. Kay and Naoum P. IssaGlomerular activation patterns and the perception
of odor mixtures (2008) European Journal of Neuroscience, pp. 1–10,