HOW INHIBITORY CONTROL MODIFIES STIMULUS VALUE AND MOTIVATION

University Of California, San Diego, La Jolla CA

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Abstract

DESCRIPTION (provided by applicant): Everyday acts of self-control directed at, for example, cigarettes, food, and gambling, depend, in part, on the ability to stop action. While much is known about action stopping in humans, real world self-control, as in the above examples, has a strong valuational or motivational component. Yet there is scant research on how motor stopping interacts with value/motivation. Our core hypothesis, based on preliminary data, is that motor stopping can reduce value and motivation. We will test three possible mechanisms based on our work with three kinds of stopping systems. Our first aim is to test how rapid stopping concurrently reduces stimulus value. We hypothesize that rapid stopping recruits a global stopping system that inhibits all currently active representations, including value. Testing this requires measuring global inhibition (with Transcranial Magnetic Stimulation, TMS), imaging the stopping system and value representations (with fMRI and Electrocorticography) and, above all, showing that brain regions critical for stopping are causally important for reducing value (using a novel form of Direct Electrical Stimulation, in humans). Our second aim is to examine how motivational stimuli, which generate action tendencies, are suppressed. Our hypothesis is that this is done by the selective stopping system that is set up according to a subject's goals in working memory and which can be triggered by the motivational stimulus itself. We will test this by measuring the temporal dynamics of motor activation and suppression with TMS, and using fMRI to examine the putative underlying fronto-striatal system. Our third aim is to leverage automatic stopping to reduce stimulus value and motivation. We hypothesize that repeated stopping (via training) generates stimulus stop-tag, so that when that stimulus occurs in the future it reactivates the stopping system (automatically), which then reduces stimulus value and motivation.