Odours result from the perception of odorant mixtures. Several studies reported that perceptual characteristics of these mixtures are often different from those of their individual components. It has been shown that odour intensity for mixtures can be higher (synergy/hyper-addition) or lower (hypo-addition) than the simple arithmetic sum of each component’s intensity. Besides, mixtures can also give rise to novel odour qualities (configural perception) or conversely are perceived as the juxtaposition of individual components’ odour quality (elemental perception). However, the biological mechanisms that govern odour mixture perception remain unclear, even if there is increasing evidence that peripheral phenomena could play an important role in mixture processing. Indeed, competitive and non-competitive interactions have been observed at the olfactory receptor (OR) and olfactory sensory neuron (OSN) levels. In this PhD work, we investigated in parallel the responses of OR, ON and human behavioural responses for three binary mixtures of odorants: Octanal (Oct) + Citronellal (Cit), Oct + Methional (Meth) and isoamyl acetate (ISO) + whiskey lactone (WL). Three types of experiments were performed: (i) in vitro OR calcium imaging of HEK293 cells; (ii) ex vivo electro-olfactogram measurement on rat OSN; (iii) psychophysical measurements in human. Our results showed clear similarities between the responses of OR/OSN and perceptual responses in human for the two mixtures Oct + Meth and ISO + WL, whereas for the Oct + Cit mixture, OR responses are hardly reconcilable with more integrated responses. Taken together, these findings support the hypothesis that interactions occurring at the peripheral level of the olfactory system contribute significantly to the olfactory coding of odour mixture
