Semantic Knowledge Influences Prewired Hedonic Responses to Odors

Background Odor hedonic perception relies on decoding the physicochemical properties of odorant molecules and can be influenced in humans by semantic knowledge. The effect of semantic knowledge on such prewired hedonic processing over the life span has remained unclear. Methodology/Principal Findings The present study measured hedonic response to odors in different age groups (children, teenagers, young adults, and seniors) and found that children and seniors, two age groups characterized by either low level of (children) or weak access to (seniors) odor semantic knowledge, processed odor hedonics more on the basis of their physicochemical properties. In contrast, in teenagers and young adults, who show better levels of semantic odor representation, the role of physicochemical properties was less marked. Conclusions/Significance These findings demonstrate for the first time that the biological determinants that make an odor pleasant or unpleasant are more powerful at either end of the life span

Pleasantness perception of odors during normal and pathological ageing

Cette thèse porte sur l'étude de la perception hédonique des odeurs au cours du vieillissement normal et de la maladie d'Alzheimer. Les deux premières études montrent une diminution du plaisir olfactif avec l'âge pour les odorants plaisants, alors que la perception hédonique reste constante pour les odorants déplaisants. L'effet est objectivé par une étude d'EEG (étude 1) montrant une diminution de la puissance béta avec l'âge spécifiquement pour les odorants plaisants, et par une étude d'IRMf (étude 2) montrant des différences d'activation entre sujets jeunes et sujets âgés beaucoup plus importantes et plus étendues pour les odeurs plaisantes que pour les odeurs déplaisantes. Les deux études suivantes montrent que ces troubles de la perception hédonique apparaissant au cours du vieillissement sont associés à une modification de certains paramètres de qualité de vie comme la prise alimentaire ou l'état nutritionnel. Ainsi, seule la perception hédonique des odeurs alimentaires est perturbée au cours de la chimiothérapie chez des séniors atteints d'un cancer du poumon (étude 3) ; et les réponses physiologiques aux odeurs varient en fonction de l'état nutritionnel chez les séniors (étude 4). Les deux dernières études (étude 5 et 6) montrent que le caractère hédonique est dévalué par les patients Alzheimer pour les odeurs plaisantes par rapport aux contrôles, mais reste constant pour les odorants déplaisants. Prises dans leur ensemble, ces données suggèrent que le vieillissement, qu'il soit normal ou pathologique, diminue le plaisir associé aux odeurs agréables et préserve en revanche le fonctionnement du système olfactif « aversif », la survie l'emportant sur le plaisirThis manuscript is about olfactory pleasantness perception during ageing and during Alzheimer disease. The two first studies of this manuscript show a decrease of olfactory pleasure for pleasant odors, whereas pleasantness perception for unpleasant odors is preserved. This effect was objectified using electroencephalography, with which we show a decrease of beta power during aging specifically for pleasant odors (study 1). Using functional MRI (study 2), we observed that the differences of activation between old young and subject subjects were much larger and more extensively spread for pleasant odors than for unpleasant odors. The two following studies show that the hedonic perception changes occurring during ageing are associated with some life quality parameters like food intake and nutritional state. The study 3 has shown that chemotherapy alters the hedonic perception for food odors (but not for non-food odors) in seniors with lung cancer. And we observed in the study 4 that physiological responses to odors were dependent on the nutritional status in older people (but not in young adults).The two last studies show that Alzheimer patients devalue pleasant odors compared to controls, whereas pleasantness perception for unpleasant odors is preserved. Taken as a whole, these data suggest that aging, whether normal or pathological, reduces the pleasure associated with pleasant smells and preserves the operation of the "aversive" olfactory system, survival outweighing pleasur

A pleasant familiar odor influences perceived stress and peripheral nervous system activity during normal aging

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Relationship Between Psychophysiological Responses to Aversive Odors and Nutritional Status During Normal Aging

International audiencePsychophysiological responses to disgusting and pleasant smells are one of the most important aspects of olfaction. These emotional signals can constitute an alert against toxic substances, and they may play a major role in food selection and nutritional intake. The aim of this study was to test this hypothesis by examining whether individual physiological responses to odors could predict the subject’s nutritional status. Because aging is associated with changes in emotional response to smells, we also examined how aging affects the relationship between olfaction and nutrition. Twenty young and 20 old participants perceived a series of odorants while their psychophysiological responses were simultaneously measured, and completed the Mini-Nutritional Assessment (MNA) questionnaire. Regression between individual correlation coefficients (r-values between odor perceptual ratings and physiological parameters) and individual MNA scores revealed that appropriateness of the physiological responses to aversive odors predicted nutritional status (R2 = 0.22, P 0.44). Taken together, preserved functioning of somatic markers in response to odors during normal aging is associated with better nutritional status, and may facilitate healthier food selectio

Effect of aging on hedonic appreciation of pleasant and unpleasant odors.

Does hedonic appreciation evolve differently for pleasant odors and unpleasant odors during normal aging? To answer this question we combined psychophysics and electro-encephalographic recordings in young and old adults. A first study showed that pleasant odorants (but not unpleasant ones) were rated as less pleasant by old adults. A second study validated this decrease in hedonic appreciation for agreeable odors and further showed that smelling these odorants decreased beta event-related synchronization in aged participants. In conclusion, the study offers new insights into the evolution of odor hedonic perception during normal aging, highlighting for the first time a change in processing pleasant odors

Evidence of peripheral olfactory adaptation: Electrophysiological recordings of the human olfactory epithelium

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Individual Differences in Verbal and Non-Verbal Affective Responses to Smells: Influence of Odor Label Across Cultures

International audienceOlfactory perception is highly variable from one person to another, as a function of individual and contextual factors. Here, we investigated the influence of 2 important factors of variation: culture and semantic information. More specifically, we tested whether cultural-specific knowledge and presence versus absence of odor names modulate odor perception, by measuring these effects in 2 populations differing in cultural background but not in language. Participants from France and Quebec, Canada, smelled 4 culture-specific and 2 non-specific odorants in 2 conditions: first without label, then with label. Their ratings of pleasantness, familiarity, edibility, and intensity were collected as well as their psychophysiological and olfactomotor responses. The results revealed significant effects of culture and semantic information, both at the verbal and non-verbal level. They also provided evidence that availability of semantic information reduced cultural differences. Semantic information had a unifying action on olfactory perception that overrode the influence of cultural background

Olfactory ratings.

<p>Means and standard errors of the mean (sem) of pleasantness and intensity in young and older adults in Experiments 1 and 2 for the 25 odorants.</p