Abstract
Motivating stimuli provoke action tendencies that sometimes lead to unwanted behavior (e.g., eating chocolate when trying to diet). Implementing control over these provocations is essential to healthy functioning; however, few laboratory-based models of such control exist. Here we developed a novel task in which thirsty human subjects made instrumental responses to obtain a juice reward (Go trials) or were required to withhold responding (NoGo trials) in the presence of a rewarded (CS+) or unrewarded (CS-) conditioned stimulus. For Go trials, single-pulse transcranial magnetic stimulation revealed a rapid increase in motor activity for CS+ versus CS-, preceding more vigorous instrumental responding. Critically, successful NoGo trials resulted in suppression of motor activity for CS+, but not CS-. Moreover, while there was broad excitation in the hand muscles in Go trials, suppression in NoGo trials was selective to the effector that could obtain reward. These results show that response suppression can be triggered by a motivational stimulus, thus providing a richer model of self-control than classic cognitive psychology paradigms.