On-line action monitoring of response execution: An electrophysiological study

In between-hand choice-RT-tasks, small incorrect EMG activations occurring before the correct response ("partial errors") are assumed to reflect the detection, inhibition and correction of erroneous hand selection, revealing the existence of an action monitoring system, acting "on-line". Now, EMG activations of the correctly selected hand muscles, too small to reach the response threshold, may also occur before these hand muscles produce an overt correct response ("partial corrects"). We hypothesized that partial corrects reflect incorrect execution of correctly selected responses. We found 1) that response force was smaller on trials preceding a partial correct trial and 2) that the Error Negativity, a performance sensitive ERP, assumed to reveal "on-line" action monitoring, was larger for partial corrects than for correct trials. This also suggests that the competence of the action monitoring system is not restricted to selection errors but also extends to execution errors.