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Dr. Micah Murray

PI of the laboratory: PD Dr. Micah Murray
Tél: 021 314 13 21
Email: micah.murray@chuv.ch

Direct supervisor (assistant): Dr. Ulrike Toepel
Tél: 021 314 13 17
Email: ulrike.toepel@chuv.ch

Department: EEG Brain Mapping Core of the Center for Biomedical Imaging (EEG-CIBM)
Address: 5, rue Pierre Decker 1011 Lausanne


Effects of Bariatric Surgery on Brain Responses to Food Viewing

Description of Project:
The student will be implicated into a interdisciplinary project between the Service of Endocrinology, Diabetes and Metabolism (SEDM) and the EEG Brain Mapping Core of the Center for Biomedical Imaging (EEG-CIBM) that aims at determining the parallels between Roux-en-Y gastric bypass (RYGB) - and its associated effects on gastric hormone levels and eating behaviour - and brain activity during the discrimination of food images. In particular, hormone blood measures will be correlated with neural responses as measured by electroencephalography (EEG) in healthy normal-weighted and obese controls without surgery, as well as in RYGB patients before and after food intake.

In obese patients with type 2 diabetes, Roux-en-Y gastric bypass (RYGB) has proven to be highly effective in improving glucose homeostasis and results in the total reversal of diabetes in 60-90% of patients. Spontaneous food intake also decreases dramatically after RYGB, without increased hunger sensations in the patients. RYGB increases glucose homeostasis by an enhanced secretion/sensitivity of the body to several hormones (e.g. insulin, glucagon-like peptide 1 GLP-1 and the peptide PYY) and decreased secretion/insensitivity to ghrelin (Rodieux et al., 2008).
The temporo-spatial dynamics of food perception have begun to be investigated by means of electroencephalography (EEG) to allow for assertions on the temporal unfolding of food-related brain activity. Toepel et al. (2009) presented normal-weighted participants with colour photographs of foods and non-foods (i.e. kitchen utensils). The food images consisted of high-energetic and low-energetic foods. Differential responses to the high- as opposed to the low-energetic foods were observed within ~200ms after image onset and involved posterior brain areas typically associated with food and object processing. Moreover, prefrontal sites typically associated with decision-making and reward processing showed varying responses as a function of the foods` energetic values. These findings suggest a rapid treatment of nutritional properties with parallel effects in brain areas thought to mediate food and object categorization, reward assessment and food-related decisions.
Whether the speed and localization of these processes are influenced by excessive obesity, its reduction by RYGB surgery, and how they can be linked with hormonal modulations before and after food intake are currently unknown.

Rodieux F, Giusti V, D'Alessio DA, Suter M, Tappy L., 2008. Effects of gastric bypass and gastric banding on glucose kinetics and gut hormone release. Obesity 16, 298-305.
Toepel U, Knebel JF, Hudry J, le Coutre J, Murray MM., 2009. The brain tracks the energetic value in food images. Neuroimage 44, 967-74.

Link to the group web site

Rue du Bugnon 9 - CH-1005 Lausanne  - Switzerland  -  Tel. +41 21 692 51 00  -  Fax +41 21 692 51 05
Swiss University