This study aims to disentangle the relative contribution of the anticipatory (food images) versus consummatory (food administration) component of dopamine release to food reward, by performing simultaneous Positron Emission Tomography (PET) and Magnetic Resonance (MR) scanning. Additionally, this study aims to assess the relationship of the dopamine release with (changes in) metabolic hormone levels.

The brain's reward system has a potent contribution to the regulation of food intake. Although animal work has demonstrated a key role of the mesolimbic dopamine system in food reward responses, evidence in humans is still sparse and inconsistent. Our research group recently used state-of-the-art Positron Emission Tomography (PET) imaging methods to study in vivo dopamine release in response to a combination of anticipatory (viewing high-calorie food images) and consummatory (drinking sips of chocolate milkshake) food stimuli in healthy women. The investigators demonstrated dopamine release in reward-related regions in the prefrontal cortex of the brain in response to these stimuli, correlating with levels of gastrointestinal hunger/satiety hormones, and predicting subsequent food intake.

The current study aims to disentangle the relative contribution of the anticipatory (food images) versus consummatory (food administration) component of dopamine release to food reward, by performing simultaneous Positron Emission Tomography (PET) and Magnetic Resonance (MR) scanning. Healthy females will participate in two PET-MR scan sessions in a fasted state: one session with the combination of anticipatory (viewing high-calorie food images) and consummatory reward (drinking sips of chocolate milkshake) and one session with purely consummatory reward. The order of these sessions will be randomized and counterbalanced.

Both scan sessions will consist of four blocks with a duration of 45 minutes each and 15 minute breaks in between. The first three blocks represent the 'control condition' and the fourth block the 'food reward condition'. At the end of each scan session, participants will take part in an ad libitum drink test in which they will be instructed to drink as much chocolate milkshake as preferred, until comfortably full. During both sessions, blood samples will be collected at several time points to assess levels of metabolic hormones and their relation to food-induced dopamine release. The proposed studies aims to increase our understanding of the psycho-biology of appetite and food intake regulation as well as identify potential new treatment targets for disorders of food intake, both at the level of the gastrointestinal tract and the brain.

Inclusion Criteria:

• Healthy females (on hormonal contraception)
• Dutch-speaking
• Right-handed
• Stable body weight with Body Mass Index (BMI) of 18.5 - 25 kg/m^2

Exclusion Criteria:

• Medical, neurological or psychiatric disorders
• Use of psychotropic medication in past 6 months
• Use of cannabis or other drugs of abuse in past 12 months
• Lactose-intolerance or food allergies
• Vegetarian diet
• Smoking
• Consumption of more than 7 alcoholic units per week
• Exposure to a significant amount of ionizing radiation in past 12 months
• Claustrophobia
• Contra-indications for Magnetic Resonance Imaging
• Pregnancy