Proactive selective response suppression is implemented via the basal ganglia

Top-down response suppression mitigates action tendencies triggered by a motivating stimulus

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.

Preparing for selective inhibition within frontostriatal loops

Action inhibition can globally prevent all motor output or selectively cancel specific actions during concurrent motor output. Here we examine the behavioral and neural basis of selective inhibition focusing on the role of preparation. In 18 healthy human participants we manipulated the extent to which they could prepare for selective inhibition by providing or withholding information on what actions might need to be stopped. We show that, on average, information improves both speed and selectivity of inhibition. Functional magnetic resonance imaging data show that preparation for selective inhibition engages the inferior frontal gyrus, supplementary motor area, and striatum. Examining interindividual differences, we find the benefit of proactive control to speed and selectivity of inhibition trade off against each other, such that an improvement in stopping speed leads to a deterioration of selectivity of inhibition, and vice versa. This trade-off is implemented through engagement of the dorsolateral prefrontal cortex and putamen. Our results suggest proactive selective inhibition is implemented within frontostriatal structures, and we provide evidence that a speed-selectivity trade-off might underlie a range of findings reported previously.

Training-induced changes in inhibitory control network activity

Despite extensive research on inhibitory control (IC) and its neural systems, the questions of whether IC can be improved with training and how the associated neural systems change are understudied. Behavioral evidence suggests that performance on IC tasks improves with training but that these gains do not transfer to other tasks, and almost nothing is known about how activation in IC-related brain regions changes with training. Human participants were randomly assigned to receive IC training (N = 30) on an adaptive version of the stop-signal task (SST) or an active sham-training (N = 30) during 10 sessions across 3 weeks. Neural activation during the SST before and after training was assessed in both groups using functional magnetic resonance imaging. Performance on the SST improved significantly more in the training group than in the control group. The pattern of neuroimaging results was consistent with a proactive control model such that activity in key parts of the IC network shifted earlier in time within the trial, becoming associated with cues that anticipated the upcoming need for IC. Specifically, activity in the inferior frontal gyrus decreased during the implementation of control (i.e., stopping) and increased during cues that preceded the implementation of IC from pretraining to post-training. Also, steeper behavioral improvement in the training group correlated with activation increases during the cue phase and decreases during implementation in the dorsolateral prefrontal cortex. These results are the first to uncover the neural pathways for training-related improvements in IC and can explain previous null findings of IC training transfer.