We have recently shown that the efficiency in stopping a response, measured using the stop signal task, is related to GABA A -mediated short-interval intracortical inhibition (SICI) in the primary motor cortex. In this study, we conducted two experiments on humans to determine whether training participants in the stop signal task within one session (Experiment 1) and across multiple sessions (Experiment 2) would increase SICI strength. For each experiment, we obtained premeasures and postmeasures of stopping efficiency and resting-state SICI, that is, during relaxed muscle activity (Experiment 1, n = 45, 15 male participants) and SICI during the stop signal task (Experiment 2, n = 44, 21 male participants). In the middle blocks of Experiment 1 and the middle sessions of Experiment 2, participants in the experimental group completed stop signal task training, whereas control participants completed a similar task without the requirement to stop a response. After training, the experimental group showed increased resting-state SICI strength (Experiment 1) and increased SICI strength during the stop signal task (Experiment 2). Although there were no overall behavioral improvements in stopping efficiency, improvements at an individual level were correlated with increases in SICI strength at rest (Experiment 1) and during successful stopping (Experiment 2). These results provide evidence of neuroplasticity in resting-state and task-related GABA A -mediated SICI in the primary motor cortex after response inhibition training. These results also suggest that SICI and stopping efficiency are temporally linked, such that a change in SICI between time points is correlated with a change in stopping efficiency between time points.

Action tendencies can be elicited by motivationally salient stimuli (e.g., appetitive rewards) or objects that support utilization behaviors. These action tendencies can benefit behavioral performance through speeded RTs in response tasks and improve detection accuracy in attentional capture tasks. However, action tendencies can be counterproductive when goals change (e.g., refraining from junk foods or abstaining from alcohol). Maintaining control over cue-elicited action tendencies is therefore critical for successful behavior modification. To better understand this relationship, we used transcranial magnetic stimulation to investigate the neural signatures of action tendencies in the presence of previously trained response cues. Participants were presented with a continuous letter stream and instructed to respond quickly to two target letters using two different response keys. Following this training phase, the target letters were embedded in a new task (test phase), and we applied transcranial magnetic stimulation to the motor cortex and measured motor evoked potentials as an index of corticospinal excitability (CSE). We found that CSE could be potentiated by a former response cue trained within a single experimental session, even when participants were instructed to withhold responses during the test phase. Critically, attention to the previously trained response cue was required to elicit the primed modulation in CSE, and successful control of this activity was accompanied by CSE suppression. These findings suggest that well-trained response cues can come to prime a conditioned action tendency and provide a model for understanding how the implementation of cognitive control can override action automaticity.