Effect of Choice on Food Pleasure Using fMRI

The study will include one inclusion session (S1), one out-of-the-magnet tasting session (S2), and one fMRI session (S3). For all sessions, study drinks used are fruit-flavored drinks and fruit juices available on the French market. All subjects will undergo the same protocol, except for the choice of the three study drinks that will be done individually.

S1. After the inclusion/exclusion criteria have been verified, the subjects will perform tests to verify their gustatory/olfactory functions (four basic tastes testing and ETOC test). They will then taste study drinks, blindly, and rate perceived pleasantness.

S2. The out-of-the-magnet tasting session will include three parts:

S2.1 - familiarization with the study procedures. Subjects will be placed in conditions mimicking the fMRI session: they will be asked to lie in supine position, head placed in a false head coil, with the gustometer fixed above their mouth and a video screen visible to them to deliver instructions (visual paradigm created using E-Prime). They also will be given a rolling wheel to collect feedback. The rest of the session will be spent in this position. Subjects will then taste the whole range of study drinks (each drink twice, in a randomized order) and rate their pleasantness on visual analog scales (VAS).

S2.2. - learning picture-drink associations. Three drinks will be chosen based on the ratings given during the first part of the session (three equally appreciated, well-liked (VAS score >50) drinks). Subjects will then taste these three drinks repeatedly while observing abstract pictures. The objective of this sequence is to learn 3 picture-drink pairs.

S2.3 - associative learning verification. Subjects will taste each of the three drinks and choose the picture to which each drink has been associated. If they fail once, the S2.2 and S2.3 sequences will be repeated. If they fail to learn associations at the second verification, they will be excluded form the study.

S3. The fMRI session's objective is to study cognitive correlates of choice. Subjects will be placed in a 3Tesla fMRI scanner, with the gustometer, visual screen and rolling wheel available as in the S2. The functional fMRI scan will be done using high-resolution protocol (1,5*1,5*1,8mm) covering prefrontal, subcortical and occipital brain areas. Subjects will undergo 80 tastings. In 50% of tastings, they will view the three previously learned pictures and freely choose one of them, then receive 1ml of the drink associated with that picture. In the other 50% of tastings, the picture-drink pair will be received without the possibility to choose. The "no choice" tastings will be computed according to the results of "choice" tastings so that each drink will be consumed the same amount of times in "choice" and "no choice" context.