WHAT IS THE FATE OF UNATTENDED EMOTIONAL STIMULI? CORTICAL AND BEHAVIOURAL CORRELATES OF AFFECTIVE HABITUATION

Previous studies have suggested that emotionally charged stimuli automatically grab attention and can be perceived without the usual capacity limitations. Recently, these results have been challenged in behavioral studies where it has been shown that the effect of high-priority verbal stimuli rapidly habituated. On the other hand, ERPs studies have shown that emotionally arousing (pleasant and unpleasant) pictures elicit larger late positive potentials (LPP) then neutral stimuli and that affective modulation of the LPP persists even after several repetitions of the same picture. However, less is known regarding affective modulation and habituation of the LLP when pictures are to be ignored and presented during a competing task. In this study, subjects were shown two digits surrounding a picture and asked to make a speeded judgment about whether the parity of the two digits matched. ERPs were measured using a 64-channel dense sensor array while participants viewed a 150 ms presentation of each stimulus consisting of two digits flanking an emotional or a neutral picture. Results suggest that reaction times weremarkedly longer for arousing, compared with neutral, pictures, but after several repetitions of the same stimuli this effect vanished. Although attention is occupied in a competing task, stimulus repetition does not appear to affect affective modulation of the LPP suggesting that categorization of unattended affective stimuli, reflected in the LPP, is an obligatory process that continues to occur whenever a sensory stimulus is presented.