Altered response evaluation - Monitoring of late responses after administration of D-amphetamine

Recently, D-amphetamine was shown to increase the error negativity, the so-called "response Ne/ERN," after incorrect choices of hand. We investigated whether this stimulation of action monitoring would also be present in the monitoring of late responses, reflected in the "late Ne/ERN." Twelve healthy volunteers performed a speeded choice-reaction task on two separate occasions on which either D-amphetamine or a placebo was administered. The results showed a clear late Ne/ERN following too late (TL) responses, but the amplitude of this late Ne/ERN was not affected by treatment condition. An error positivity (Pe) was present after the late Ne/ERN in the placebo condition, but not in the amphetamine condition. Also, P2a amplitudes following TL feedback were larger after administration of amphetamine compared to placebo. Questionnaires filled in by participants showed that they overrated their own speed and accuracy after administration of amphetamine. Overall, this suggests that the stimulating aspects of amphetamine lead to changes in affective and motivational evaluation of errors and performance in general. Therefore, along with the established cognitive contributions, the current results provide evidence for an important role of affective processes in action monitoring and the effects they have on accompanying ERP components.