Platonov Artem, Goossens Jeroen
Radboud University Medical Centre Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Department of Cognitive Neuroscience, Section Biophysics, Nijmegen, The Netherlands.
J Vis. 2013 May 28;13(6):12. doi: 10.1167/13.6.12.
It is generally believed that percept alternations in binocular rivalry result from the interplay between mutual inhibition and slow adaptation of the competing percepts. This view is supported by growing evidence that dynamic changes in adaptation indeed support percept alternations in binocular rivalry. Empirical evidence for the involvement of mutual inhibition, however, is still scarce. To fill this gap, we presented human subjects with dichoptic random-dot motion stimuli and manipulated the angle between the monocular directions of motion from pure opponent horizontal motion to pure vertical motion in the same direction. We hypothesized that this decrease in motion-direction disparity increases the cross-inhibition gain due to lateral inhibition between neurons in the brain that are coarsely tuned to adjacent directions of visual motion, which predicts the largest changes in dominance at the smallest instead of the largest motion-direction disparities. We found that decreasing the angle between the two monocular directions of motion indeed systematically increased the predominance and mean dominance durations of the motion pattern presented to the ocular dominant eye (as identified by the hole-in-card test). Moreover, this effect was stronger if the contrast of the stimuli was lowered. Simulations showed that these features are indeed hallmark of weighted lateral inhibition between populations of directionally tuned motion-sensitive neurons. Our findings thus suggest dominance and suppression in binocular rivalry arises naturally from this fundamental principle in sensory processing. Interestingly, if the two monocular directions of motion differed <60°, the percept alternations also included transitions to in-between (vertical) motion percepts. We speculate that this behavior might result from positive feedback arising from adapting disinhibitory circuits in the network.
人们普遍认为，双眼竞争中的知觉交替是由相互抑制和竞争知觉的缓慢适应之间的相互作用引起的。越来越多的证据支持这一观点，即适应的动态变化确实支持双眼竞争中的知觉交替。然而，关于相互抑制参与其中的实证证据仍然很少。为了填补这一空白，我们向人类受试者呈现了双眼分视的随机点运动刺激，并操纵了单眼运动方向之间的角度，从纯相反的水平运动到同一方向的纯垂直运动。我们假设，运动方向差异的减小会增加交叉抑制增益，这是由于大脑中对相邻视觉运动方向进行粗略调谐的神经元之间的侧向抑制，这预测在最小而非最大的运动方向差异处优势度会有最大变化。我们发现，减小两个单眼运动方向之间的角度确实会系统性地增加呈现给优势眼（通过卡片打孔测试确定）的运动模式的优势度和平均优势持续时间。此外，如果刺激的对比度降低，这种效应会更强。模拟结果表明，这些特征确实是方向调谐的运动敏感神经元群体之间加权侧向抑制的标志。因此，我们的研究结果表明，双眼竞争中的优势和抑制自然地源于感觉处理中的这一基本原理。有趣的是，如果两个单眼运动方向的差异小于60°，知觉交替还包括向中间（垂直）运动知觉的转变。我们推测，这种行为可能是由网络中适应性去抑制回路产生的正反馈导致的。
