Abstract
Drifting grating patterns with different motion directions independently presented to the two eyes induce two perceptual interpretations (Andrews & Blakemore, 2002). One is “pattern motion” that forms a superimposed pattern moving with a single direction, equivalent to the vector sum of the two motion directions. The other is “component motion” that forms two independent motion directions followed by monocular dominance in which one eye's motion is perceived alone. Although this perceptual process involves not only interocular rivalry (right or left eye's image) but also motion-type rivalry (pattern or component motion), most of the previous studies discussed only one of those rivalries independently. Here we studied this double rivalry process during binocular rivalry of motion direction in terms of the temporal order of each rivalry. We measured reaction times (RTs) using a visual stimulus for which the probability of each perceptual interpretation was approximately equal. RTs to perceive a consistent motion direction in pattern and component motion conditions were 400 ms and 750 ms slower, respectively, than that in the condition when identical motion stimuli were presented to the two eyes. We further measured magnetoencephalography (MEG) signal evoked by the corresponding visual stimulus condition, indicating significant difference in the RMS amplitude between the two perceptual interpretations (pattern or component motion) in the latency range consistent to the RT measurement. These results suggested that motion-type rivalry was resolved before interocular rivalry and these rivalries in motion perception were processed hierarchically.