Lateralized effect of affective picture processing: a visual evoked potential study

Particular qualities of pictures may elicit an emotional response that varies according to valence and arousing properties of the stimuli. Moreover emotional arousal produced by certain situations can promote memory storage. Our purpose was to investigate modifications of visual evoked potentials (VEPs) and assess their relationship to hemispheric asymmetry during the presentation of standardized emotional pictures; to evaluate affective memory, free recall test was performed. Sixty slides, selected from the International Affective Picture System (IAPS), were presented for 2 sec to 26 subjects. VEPs were recorded from Oz, Pz, Fz, P3, P4, Cz locations. Analyses were performed on both amplitudes and latencies of P300 peak. The self-report measures showed a high level of accordance among the subjects in the evaluation of the emotional valence. The self-assessed emotional reactions of men and women to the slides did not differ. The analysis of peak amplitude and latency of P300 revealed a highly significant valence effect. Larger amplitudes were revealed when unpleasant slides were presented, as compared to pleasant and neutral ones; the higher peak latency in P3 electrode site, compared to P4, shows a stronger activation of the right hemisphere, compared to the left one. The free recall of the projected slides showed that the emotional content influences memory. Memory for emotional stimuli was higher compared to neutral ones. These results indicate a lateralized effect of affective picture processing. Moreover, VEPs and memory data showed a similar pattern: both unpleasant and pleasant slides induced higher amplitudes of P300 and were better remembered than neutral slides.