To do or not to do? Action enlarges the FRN and P300 effects in outcome evaluation.

Behavioral studies demonstrate that the outcome following an individual's action evokes stronger emotional responses than the same outcome following inaction. Here we use the event-related potential (ERP) technique to investigate how action affects the brain activity in outcome evaluation. In a gambling task, participants were asked to select a box from three boxes containing monetary reward and then to decide whether they would change their initial choice (i.e., action) or not (i.e., inaction). The feedback-related negativity (FRN), an evoked potential that peaks approximately 250 ms after receipt of feedback information, showed a larger differential effect between loss and win following action than following inaction. Similarly, the P300 showed a larger differential effect following action than following inaction, but now with the responses more positive to the win feedback than to the loss feedback. These results suggest that action may increase the expectancy towards the outcome and/or the motivational/emotional significance of the outcome, and that this action effect can be found in both the FRN and the P300 electrophysiological responses.