A randomized controlled experimental medicine study of ghrelin in value-based decision making

Area of Science:

• Neuroscience
• Endocrinology
• Decision Science

Background:

• Ghrelin, a stomach hormone, stimulates appetite and its receptor is found in brain reward circuits.
• Previous research focused on ghrelin's role in food and drug reward.
• This study investigates ghrelin's impact on non-food/drug monetary reward decision-making.

Purpose of the Study:

• To investigate the effects of ghrelin on human decision-making processes concerning monetary rewards.
• To determine if ghrelin influences reward anticipation and value assessment beyond its known appetite-stimulating functions.

Main Methods:

• Thirty participants (50% male, 50% female) underwent two functional magnetic resonance imaging (fMRI) scans.
• Participants received intravenous ghrelin or a saline placebo in a randomized, counterbalanced order.
• Decision-making tasks involving monetary rewards and losses were administered during fMRI scans.

Main Results:

• Ghrelin did not affect reward anticipation in the striatum but attenuated activity during anticipation of losses.
• Temporal discounting rates for monetary rewards were lower under ghrelin, an effect more pronounced in women.
• Neural activity in the left parietal lobule, including the angular gyrus, correlated with discounting rates and was suppressed by ghrelin.

Conclusions:

• This is the first human study to explore ghrelin's role in monetary decision-making outside the feeding or addiction domains.
• Ghrelin attenuated loss aversion and reduced temporal discounting of monetary rewards, contrary to initial hypotheses.
• Ghrelin may induce a motivational shift towards caloric rewards rather than globally enhancing reward value.