Affective engagement and subsequent visual processing: effects of contrast and spatial frequency.

The present study examined if viewing affective stimuli alters subsequent visual processing, as indexed by steady-state visual potentials (ssVEPs) and behavioral performance in an orientation discrimination task. Participants viewed task-irrelevant but emotionally arousing pictures from the International Affective Picture System (1 s) followed by a target stimulus stream consisting of low (2 cpd) or high-spatial frequency (6 cpd) Gabor patches, flickering at a temporal rate of 14 Hz. Luminance contrast of the patches gradually increased for the first half and decreased for the second half of the total duration, resulting in a waxing-waning pattern of stimulus contrast. The authors found that the waveform envelope of 14 Hz-ssVEPs corresponded to time-varying stimulus contrast. Analyses compared medium- and high-contrast time segments, as a function of emotional content and spatial frequency. Results showed greater ssVEP amplitudes for patches with high compared to medium contrast. Viewing emotionally arousing pictures selectively enhanced the ssVEP amplitudes for low-spatial frequency target patches and attenuated the ssVEP evoked by high-spatial frequency patches, across contrast levels. Response times were slower for patches following unpleasant pictures rather than pleasant and neutral, and error rates mirrored the interaction of emotional content and spatial frequency observed in the ssVEP data. Together, the present results suggest that additive gain mechanisms and early visual pathways may mediate costs and benefits of emotional engagement for subsequent sensory processing.