Abstract
When two different stimuli are dichoptically presented to the two eyes, observers experience alternating views of these two stimuli, so called binocular rivalry. It is well accepted that the competing stimuli need to be presented for longer than 100 ms to establish rivalry dominance. It is also shown that the rivalry switch can be stabilized if the two stimuli are presented intermittently. In this study, we investigated whether interocular inhibition could occur within the first 100 ms of stimulus presentation following repeated intermittent but very brief presentations of competing stimuli. Furthermore, we tested whether a stabilization effect could be established for very briefly presented stimuli. A vertical and a horizontal grating were dichoptically presented to the subjects' two eyes for 70 ms, every two seconds. Subjects perceived the mixture of the gratings during the initial variable number of trials. Gradually their percept was stabilized to one of the two gratings. The perceptual dominance of one stimulus was measured with a monocularly presented 20-ms flash probe. The two eyes showed dramatically different sensitivities to the probe after perceptual dominance was established. The inter-eye sensitivity difference was the highest when the probe was presented simultaneously with the gratings. Interestingly, such a sensitivity difference was still observed 50 ms after the removal of the stimuli, but dropped significantly after 150 ms. These results suggest that when presented with two competing stimuli, the suppressive interaction between the two eyes can accumulate across temporal gaps of stimulus presentation. Following many trials of very briefly presented competing stimuli, the interocular suppression is engaged immediately at the beginning of stimulus presentation. Our data also suggest that during these temporal gaps, the sensitivity difference between the two eyes decays relatively rapidly, yet the polarity, and possibly the strength, of interocular suppression is maintained across trials.
This research was supported by the James S. McDonnell foundation, the US National Institutes of Health Grant R01 EY015261-01.