Evolutionary grass roots for odor recognition

Adding odor: Less distress and enhanced attention for 6-month-olds

The effect of odor on cognitive and emotional processes has been studied in adults and children, but less so in infants. In this study twenty-seven six-month-olds were presented with a video while in either an odor (pine or baby-powder) or a no odor control condition. The video was a 92-s audiovisual presentation of a woman expressing happiness and sadness, with the order of emotion counterbalanced. Infant attention (looking time) and emotional expression (smiling, crying, mouthing) were coded. Infants looked longer in the presence of odor and expressed less crying and mouthing but more smiling behavior. Presence of odor markedly reduced infant emotional distress and increased attention, suggesting that the olfactory sensory system provides cues to infants that support mood regulation and maintain attention. These results have implications for optimizing infant environments for emotional health and cognitive development.

Interactions of odorants with olfactory receptors and other preprocessing mechanisms: how complex and difficult to predict?

In this issue of Chemical Senses, Münch et al. present a thorough analysis of how mixtures of odorants interact with olfactory receptors (ORs) borne by olfactory receptor neurons (ORNs). Using fruit fly ORNs expressing the receptor OR22a, they provide a clear example of mixture interaction and confirm that the response of an ORN to a binary mixture can be sometimes predicted quantitatively knowing the ORN responses to its components as shown previously in rat ORNs. The prediction is based on a nonlinear model that assumes a classical 2-step activation of the OR and competition of the 2 odorants in the mixture for the same binding site. Can this success be generalized to all odorant-receptor pairs? This would be an encouraging perspective, especially for the fragrance and flavor industries, as it would permit the prediction of all mixtures. To address this question, I outline its conceptual framework and discuss the variety of mixture interactions found so far. In accordance with the effects described in the study of other receptors, several kinds of mixture interactions have been found that are not easily predictable. The relative importance of the predictable and less predictable effects thus appears as a major issue for future developments.