Effects of emotional arousal in the cerebral hemispheres: a study of oscillatory brain activity and event-related potentials

Objective: The present study aimed at examining the time course and topogra phy of oscillatory brain activity and event-related potentials (ERPs) in re sponse to laterally presented affective pictures. Methods: Electroencephalography was recorded from 129 electrodes in 10 heal thy university students during presentation of pictures from the internatio nal affective picture system. Frequency measures and ERPs were obtained for pleasant, neutral. and unpleasant pictures. Results: In accordance with previous reports, a modulation of the late posi tive ERP wave at parietal recording sites was found as a function of emotio nal arousal. Early mid gamma band activity (GBA; 30-45 Hz) at 80 ms post-st imulus was enhanced in response to aversive stimuli only, whereas the highe r GBA (46-65 Hz) at 500 ms showed an enhancement of arousing, compared to n eutral pictures. ERP and late gamma effects showed a pronounced right-hemis phere preponderance, but differed in terms of topographical distribution. Conclusions: Late gamma activity may represent a correlate of widespread co rtical networks processing different aspects of emotionally arousing visual objects. In contrast, differences between affective categories in early ga mma activity might reflect fast detection of aversive stimulus features. (C ) 2001 Elsevier Science Ireland Ltd. All rights reserved.