N1 and N2 ERPs reflect the regulation of automatic approach tendencies to positive stimuli

The Approach-Avoidance Task (AAT) measures automatic approach-avoidance tendencies and their regulation: compatible reactions (approach positive, avoid negative) are faster than incompatible ones (approach negative, avoid positive). The present study assessed event-related potentials (ERPs) in 15 healthy persons for depicting neuropsychological sub-processes of such stimulus-response compatibility (SRC) effects. Early attention allocation preparing efficient stimulus classification (N1 ERP) and response inhibition on the level of response representations (N2 ERP) were found to underlie the solution of the AAT-conflict. For positive stimuli, these processes were enhanced during the incompatible condition avoid positive compared to the compatible condition approach positive. Source localization analysis revealed activity in right occipital areas (N1 ERP), and in left DLPFC and insula (N2 ERP) to be neuronal generators of these electrophysiological SRC effects. This neuronal regulation resulted in no influence of incompatibility at the behavioural level. For negative pictures, we found the reversed pattern: there were no electrophysiological SRC effects, but clear behavioural SRC effects in both RTs and error frequency, i.e. participants were faster and made fewer errors during avoiding than approaching negative pictures. These valence-specific differences are in line with previous studies indicating negative stimuli - probably due to higher importance for survival - to more strongly influence behaviour.