A METHOD FOR INVESTIGATING BINOCULAR-RIVALRY IN REAL-TIME WITH THE STEADY-STATE VEP

Under conditions in which the visual system cannot reconcile dissimila r images from the two eyes, perception typically alternates between th e two half-images - a process known as binocular rivalry. We report a real-time, steady-state VEP method that is a sensitive detector of the continuous alternations in perceptual dominance across the eyes, This method works by labeling each half-image with a slightly different te mporal frequency so that the record generated by each can be recovered from the EEG by spectrum analysis. In this way, one can track the ''w axing'' and ''waning'' of the VEP amplitudes for each eye simultaneous ly during spontaneous rivalry, permitting an analysis of the relative physiological dominance of each eye in real-time, Such alternations we re clearly observed in the VEP amplitudes generated by each half-image during rivalry (the amplitudes for the two eyes correlated negatively ). In contrast, VEP amplitudes for the two eyes varied either synchron ously or randomly when the half-images were allowed to fuse. The insta nces of physiological dominance of each eye as evidenced by the VEP co rrelated well with the subjects' report of perceptual dominance, This purely electrophysiological method appears to be suitable for measurin g rivalry in non-verbal human or animal subjects, as it does not requi re active participation from them. (C) 1997 Elsevier Science Ltd.