Electrophysiological signatures of the race model in human primary motor cortex

For 30 years, the independent race model has been used to account for the attempt to reactively inhibit on-going responses in the stop-signal task (reactive behavioral inhibition). The success of the race model derives in part by assuming that motor response activation speed is not different on inhibition trials compared to trials where inhibition is not required. To date, neurophysiological evidence supporting this assumption (context independence) has been limited, especially in human participants. In this study, we used EEG to investigate stop-signal task performance in human participants, focusing on lateralized readiness potentials (LRPs) to examine context independence in human primary motor cortex (M1). The current results provided support for the context independence assumption, and further showed that successful inhibition was largely contingent upon the timing of response activation in M1 relative to stop-signal onset. These data afford a valuable insight into how stop-signal response inhibition is effected in the human brain.