tVNS Effects on Motivation in Depression

Attaining goals or rewards commonly entails response costs. In light of cost and benefits, how do participants decide what effort should be put in to give it a shot? Figuratively, you may "go with your gut", but the literal contribution of the gut-brain axis in allocating effort is poorly understood to date. Here, the investigators propose to investigate non-invasive transcutaneous vagal nerve stimulation (tVNS) as a potential modulator of energy metabolism and response vigor. Since the neural mechanisms causing the diverse cognitive and behavioral effects of the stimulation remain largely elusive, the investigators will use computational modeling of instrumental behavior and determine the primary metabolic effects of the stimulation. The investigators hypothesize that tVNS will lead to activation of afferent targets in the brain. In turn, the elicited brain activation is expected to mediate the cognitive effects of the stimulation. This may affect both sides of the utility equation because anti-depressive effects may correspond to boosting the benefit of effort whereas anti-nociceptive effects may reduce perceived costs of effort. Collectively, dissecting the cognitive effects of non-invasive tVNS in healthy individuals may facilitate the more widespread use as a treatment in mental disorders that are characterized by metabolic alterations such as depression.