Amygdala hyperactivation relates to eating behavior: a potential indicator of food addiction in Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a rare genetic neurodevelopmental disorder involving nutritional, endocrine /metabolic, emotional and behavior dimensions. There is evidence for impaired hypothalamic development and function in PWS, involving oxytocin and ghrelin, which can account for the typical PWS phenotype. Hyperphagia with addiction-like behavior is one of the common features of PWS and is a consequence of the hypothalamic dysfunction. In this study, we hypothesized that brain regions associated with compulsive eating behavior would be abnormally activated by food-related odors in PWS, as these can stimulate the appetite and induce hunger-related behavior. Methods We used a classic olfactory discrimination test to verify that olfaction was normal in patients with PWS. In an fMRI scanner, we presented two odors, a tulip and a caramel odor, which have a different hedonic valence and a different capacity to arouse hunger-related behavior. Results There was a five-fold higher activation in the right amygdala for the caramel odor compared with the tulip odor in patients with PWS (n=14). No such hyperactivation was found in age-matched controls (n=11). Cluster analysis of clinical hyperphagia scores in patients with PWS revealed a link with the right amygdala hyperactivation. Conclusions Our study provides evidence for functional alteration of the right amygdala in PWS, which is part of the brain reward network involved in food addiction. This finding may relate to dysfunction of the ghrelin and oxytocin systems in PWS, as these are involved in addictive behavior, appetite, and olfactory bulb regulation. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by grants from the Foundation for Prader Willi Research (ComuFace FPWR OTP 53675) to JD, BP, and MT) and recurrent funding from the Centre National de la Recherche Scientifique (CNRS) (to PB, JD, and KS). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the ethics committee Comite de Protection des Personnes Sud-Ouest et Outremer 1, Toulouse Hospital CHU 13687203; National EudraCT 201300437-33. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors