6533b7d5fe1ef96bd1264318

RESEARCH PRODUCT

Brain mechanisms of the odor-induced taste enhancement in people living with normalweight and obesity: sensory and electroencephalography studies

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Some odors have the property of enhancing the taste perception, whether it is sweet, salty, acidic or umami. It is therefore possible to enhance the perception of a taste by using odorant ingredients in food. The integration of taste and odor results in the perception of a unique quality for the food, called the flavor. The mechanism that results from this integration, called odor-induced taste enhancement (OITE), has been little studied in the literature in normal weight (NW) and obese (OB) individuals. It has been observed that the odor-induced taste enhancement is higher in OB compared to NP, for a single product tested. The brain structures involved in OITE have already been identified, but no study has compared this flavor network between populations of different weight status. Moreover, the organization of the flavor network and the identification of the integrating areas remain poorly studied. In the obese individual, some of these brain structures show a reduction in grey matter density which could lead to a reduction in the functionality of these brain areas. The aim of this thesis was twofold, i) to identify variations in OITE between OB and NW populations and ii) to identify brain mechanisms that allow the OITE in both normalweight and obese individuals. In particular, we were interested in the temporal course of information processing leading to OITE. This thesis work is divided into 2 main research axes and 4 studies. The first axis concerns the study of weight gain (obesity) on the perception of OITE by sensory evaluation methods. The first study allowed the development of a sensory evaluation method based on a classification task in order to highlight OITE. The second study aimed to test 17 sweet and salty drinks to investigate the perceptual variability of OITE between the two populations. Our results show that OITE is more prominent and present in OB than in NW. Moreover, some enhancements were population-specific, which points towards a different exposure to the tested flavors, related to diets. The second axis of research focused on highlighting the organization of the cerebral network of the flavor and the comparison of the OITE networks between the two populations. The third study optimized an experimental design of stimulation favoring a maximal and rapid release of odorants through the retronasal pathway, in EEG conditions. Finally, in a fourth study, the brain organization of OITE was compared in both populations for 4 sweet and salty solutions. The first EEG results seem to confirm the integration of odor and taste in high-level brain structures in both groups. These high-level brain areas would project feedback loops to the primary sensory areas to produce OITE. Moreover, in people with obesity, we identified that late information processing was lower. Despite the lower amplitude, we can imagine that neurons would gain in efficiency, by increasing the number of synapses to process information leading to a more important OITE, observed in people living with obesity.