Error awareness in a saccade countermanding task

Stop-signal tasks can be used to analyze mechanisms of action control and error monitoring. Previous event-related potential (ERP) studies indicated enhanced stop-signal N2 amplitudes for unsuccessful compared with successful inhibition. The aim of this study was to further investigate whether stop-signal related and response-related ERP components would reflect different aspects of error processing. ERPs were recorded during a saccade countermanding task, i.e. a stop-signal task with oculomotor response. Error awareness was obtained from subjective accuracy ratings. The response-related error positivity (Pe) was more pronounced for perceived than for unperceived errors whereas awareness of an error did not modulate the magnitude of the error negativity (Ne). This result is in accordance with previous findings. Stop-signal related ERPs revealed enhanced N2 amplitudes for incorrect (unsuccessfully stopped) trials compared with correct trials. However, this enhancement was restricted to perceived errors. The results support the idea that the stop-signal itself provides a performance feedback and the N2 reflects aspects of conscious response monitoring of unsuccessful inhibition.