Timing of response differentiation in human motor cortex during a speeded Go/No-Go task

•The temporal dynamics of response inhibition was investigated.•Subjects performed a Go/No-Go task under time pressure.•TMS probes were used to assess motor cortical excitability during the task.•Distinction in motor cortical excitability was evident by 90ms based on cue type.•Results suggest a rapid ability of the brain to stop unwanted but pre-potent action. We explored the brain's ability to quickly prevent a pre-potent but unwanted motor response. To address this, transcranial magnetic stimulation was delivered over the motor cortex (hand representation) to probe excitability changes immediately after somatosensory cues prompted subjects to either move as fast as possible or withhold movement. Our results showed a difference in motor cortical excitability 90ms post-stimulus contingent on cues to either promote or prevent movement. We suggest that our study design emphasizing response speed coupled with well-defined early probes allowed us to extend upon similar past investigations into the timing of response inhibition.