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Marzia Del Zotto, Marie-Pierre Deiber, Lore B. Legrand, Alan J. Pegna; Brain oscillatory activity related to biologically relevant visual stimuli in a patient with affective blindsight.. Journal of Vision 2013;13(9):1134. doi: 10.1167/13.9.1134.
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© ARVO (1962-2015); The Authors (2016-present)
Studies of cortical blindness have suggested that some residual visual function may persist despite the absence of perceptual consciousness. Here, a 60 year-old male patient (TN) with affective blindsight was tested to search for electrophysiological evidence of unconscious processing for biologically relevant stimuli (e.g. emotional faces and naked bodies). We carried out two different spatial attention-cueing experiments, in which we randomly presented facial expressions (fearful, happy and neutral) and female bodies (naked and dressed) as cues for 1000 ms, followed by an auditory target (500 Hz) to the right or left ear. TN was asked to respond to the auditory stimulus by pressing a button on the side of its appearance. We performed a 128-channel EEG recording and a time-frequency analysis using continuous wavelet transform, extracting all frequencies between 4 and 30Hz. We performed t-test analyses on cue-locked epochs of 4000 ms starting 1000 ms before cue onset, comparing positive vs. negative emotions as well as naked vs. dressed bodies. We found significant differences between fearful and happy faces over the right ventral frontal leads in the 7-8Hz range at 150-400 ms, and between happy and neutral as well as between fearful and neutral faces over the left ventral frontal electrodes in the 12-13Hz range, at 180 and 280 ms after cue onset. Finally, naked stimuli produced an event-related desynchronization (ERD) at 14-15Hz in the 140-180 ms period, as well as at 10-13Hz in the 740-840 ms period over centro-parietal areas. Our results suggest that emotional faces can be processed at a very early stage in the absence of awareness, producing significant effects in the low alpha band over right frontal channels with emotional valence, and modulating the high alpha band over left frontal electrodes with arousal. Alpha ERD thus appears to reflect unconscious perception of biologically relevant stimuli.
Meeting abstract presented at VSS 2013
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