Human cortical activities during Go/NoGo tasks with opposite motor control paradigms

The purpose of this study was to investigate the cortical activities during two types of Go/NoGo task with different movement instructions (Push-Go and Release-Go) using transcranial magnetic stimulation (TMS) and event-related potential (ERP) recordings. In the Push-Go condition, ten subjects were instructed either to push a button with their right index finger as fast as possible after a Go signal or not to push it after a NoGo signal. In the Release-Go condition, they were asked beforehand to continually depress a button by pushing, and instructed either to release it as fast as possible after a Go signal or not to release it after a NoGo signal. TMS was applied to the left primary motor cortex at 20--300 ms after each signal. In the Push-Go condition trials, the amplitude of the motor evoked potentials (MEPs) recorded from the right first dorsal interosseous muscle significantly increased at 120--300 ms after the Go signals and decreased at 160--200 ms after the NoGo signals. In contrast, the MEP amplitudes recorded during the Release-Go condition trials significantly decreased at 160--300 ms after the Go signals and significantly increased at 160--180 and 220--300 ms after the NoGo signals. On the other hand, the ERPs recorded in the frontocentral cortex after each signal for five of the subjects were identical in both the Push-Go and Release-Go condition trials. These results indicated that, while the cortical activities related to the Go/NoGo decision were similar in the two task conditions, the corticospinal excitability was modulated so as to suppress or facilitate the required Go responses depending on the given movement instructions. This suggests that the Go/NoGo decision may be separate from the subsequent motor program.