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Chapter 7
Abstract
Motivational, cognitive and action goals have been proposed to be processed by distinct
corticostriatal circuits that are organized hierarchically. Reward motivation has been
proposed to influence cognitive and motor processing via guiding information flow through
an anterior/ventromedial to posterior/dorsolateral cascade of topographically specific regions
of the striatum and frontal cortex. Here we tested this hypothesis in human volunteers by
investigating effects of offline transcranial magnetic stimulation of distinct frontal regions
associated with reward, cognition and action processing, on task-related signaling in distinct
regions of the striatum. Immediately after stimulation of the anterior prefrontal cortex
(aPFC), the dorsolateral prefrontal cortex, or the premotor cortex, participants performed an
established paradigm assessing reward anticipation (motivation), task switching (cognition),
response switching (action) and their integration, while neural responses were measured
with functional magnetic resonance imaging (fMRI). Stimulation of the aPFC, and not of
the other cortical regions, decreased reward-related processing in the caudate nucleus, while
it decreased processing in the putamen during the interaction of reward, task switching and
response switching. Thus stimulation of the aPFC altered processing in distinct regions of
the striatum as a function of task demands, providing evidence for a functional cascade of
processing across corticostriatal circuits via the striatum.