Predicting binocular rivalry alternations from brain activity

Abstract

When each eye views a different stimulus, visual perception alternates irregularly between them: binocular rivalry. One theory is that: reciprocal inhibition between neurons processing the two stimuli yields active (dominant) and suppressed neurons—we see the stimulus processed by active neurons; adaptation of active neurons eventually reverses activity—perception changes. We know that highly active neurons adapt faster than sluggishly active neurons. Hence, if we had some way of measuring the early activity of the active population, we could predict when a rivalry alternation will take place. We used electroencephalography (EEG) to measure brain activity to a 1000-ms display of dichoptic, orthogonally oriented, sine-wave gratings. Then we turned off both gratings for a 200-ms, dark gap, before showing the same rival gratings for another 1000 ms. We followed this by a mask then an inter-trial interval (ITI). Thirteen participants pressed keys during the ITI of numerous trials to say whether perception changed at the gap or not. Each participant also responded to numerous non-rivalry trials in which the gratings had identical orientations for the two eyes and for which the orientation of both either changed physically at the gap or did not. We found, with simple averaging (rather than requiring pattern classifiers), that greater activity about 180 ms after initial onset of rival stimuli predicted a change in perception more than 1000 ms later, after the gap. We conclude that the predictive activity is consistent with adaptation’s being responsible for binocular rivalry alternations.