6. Olfactory integration and odour perception
Résumé
The olfactory system has to process the limitless chemical world of odours. Everything begins in the nose in which, the volatile odorant molecules enter in rhythm with our breathing. On the forefront are the olfactory sensory neurons (OSNs) which process sensory information by integrating simultaneously, as soon as the first sniff, quantitative, qualitative and temporal features of stimuli and, send to the next level, the olfactory bulb (OB) a well-defined description of stimulus attributes. At the OB level, the incoming peripheral message is sorted and in so doing designs an incident functional map. At this level, the sensory information is furthermore amplified, filtered and transformed, this probably resulting in an olfactory code based on fine temporal tuning of spike activities within mitral-tufted neuron assemblies. Such a multiplexed code based on both temporal and frequency parameters would further use gamma oscillations as a global clock and appears as especially adapted to face multidimensional stimuli which inputs are fragmented across OB. Then the processed olfactory information diverges to the piriform cortex where the olfactory percept forms. At the next stage, the olfactory information is combined together with the information from other sensory organs and compared with previous experiences to give the final odour perception. As all the other senses, olfaction can display genetic, gender and aging variations in performances. In addition, the olfactory function can be impacted by stress, circadian rhythm and in women by the reproductive neuro-endocrine status.
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