The fruits of your labor: Neuromodulatory effects of effort and endocrine signals on food reward

• Applicant: Professor Dr. Nils Kroemer
• Subject Area: Clinical Psychiatry, Psychotherapy, Child and Adolescent Psychiatry ; Human Cognitive and Systems Neuroscience
• Term: from 2014 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258752742

In everyday life, reward and effort are entangled. Economic theories of utility posit that effort required to obtain certain rewards is reflected in discounting of the attributed value. In contrast, philosophical and psychological theories tracing back to ancient Greece have emphasized that effort may eventually increase the perceived value of a reward in retrospect (dubbed as IKEA effect recently). Yet, there has been no experimental approach to integrate these lines of research into a coherent framework. Using functional magnetic resonance imaging (fMRI), the research objective is to investigate the neural correlates of the modulatory effect of effort on reward processing. In the proposed paradigm, participants will be shown a stimulus that indicates the amount of a palatable drink to be delivered inside the scanner. The palatable drink has to be collected by investing more or less motor effort which is visualized by the distance of a symbolic agent to the target cue. After the response phase, the drink will be delivered inside the scanner. Effect size calculations indicate that 25 participants, sampled from a diverse range of body mass index (BMI), will have to be investigated in order to detect a) a main effect of perceived effort, b) invested effort, and c) a potential correlation with BMI of medium size. I hypothesize that perceived effort attenuates the value signal in the mesocorticolimbic pathway during the anticipatory phase, whereas invested effort may lead to stronger reward processing during the consummatory phase in the dopaminergic system and the insula. Moreover, I expect that homeostatic signals which are known to modulate dopaminergic function (i.e., insulin, glucose, leptin, and ghrelin) will modulate the correspondence between effort and reward processing of the palatable drinks. Ultimately, I argue that understanding motivational biases in flavor perception may help to better understand the current obesity epidemic which might be promoted by the availability of effortless fast-food options.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Dana M Small, Ph.D.