Automatic processing of valence differences in emotionally negative stimuli: evidence from an ERP study.

The present study investigated the influence of attention on the human sensitivity to valence differences in emotionally negative stimuli. Event-related potentials were recorded for unattended highly negative (EN), moderately negative (MN) and neutral pictures in Experiment 1 which engaged subjects in an auditory discrimination task; and for EN, MN and neutral pictures in Experiment 2 that required visual classification of pictures. Results of both experiments displayed increased negative deflections during EN than during MN and neutral conditions at 150-250, 250-350, and 350-450 ms intervals post-stimulus. Moreover, MN stimuli elicited larger negativity than did neutral stimuli during 250-350 ms interval in either experiment. This developed our understanding of the human sensitivity to valence differences in negative stimuli, by revealing that the brain sensitivity to the valence strength of negative stimuli exists stably, unaffected by attention access to some extent.