How odor transcends taste differently between individual with normal weight and individual living with obesity: time frequency analysis of EEG

International audienceWorldwide prevalence for obesity has tripled between 1975 and 2016 with a staggering number of 2.8 million individuals succumbing to this disease as of 2021. To address this issue, one of recommendations by WHO was to reduce salt/sugar consumption. It has been shown that aroma can increase taste’s intensity perception, a phenomenon known as odor-induced taste enhancement (OITE). However, the underlying neural mechanisms of this phenomenon remain unknown. Hence, we aimed to better understand the neural mechanisms of odor-induced taste enhancement between normal weight (NW) individuals and individuals with obesity (OB). Here, we proposed to probe the brains’ responses of OITE with electroencephalography (EEG) by employing time-frequency analysis approach to measure the event-related (de)synchronization (ERDS). In this EEG experiment, 33 NW and 28 OB evaluated the intensity of three solutions, i.e., odour (vanillin), taste (sucrose) and flavor (vanillin + sucrose). We anticipated that if OITE occurs, there would be a higher synchronized activity in the flavor condition when compared to the taste condition. Across both groups, EEG results revealed synchronization activity in the delta band (1Hz-4Hz), and these synchronized activity differs between condition and time points. Importantly, we found a significant increase of synchronized activity (600ms-800ms) at the temporal region for flavor; (230m-1000ms) for taste but not for odor. Within groups, only OB group showed a significant increase between the early and late period, suggesting an OITE effect. These results suggest that OITE induced by the integration between taste and odour is a late brain processing phenomenon. Taken together, we propose that OITE may involve a ‘feedback loop’ mechanisms that reactivates the taste cortex following integration, and that OITE demostrated promising potential in addressing the issue of reducing sugar intake for OB