认知与发展心理学研究室知识库

长久以来，视觉后像(Afterimage)的形成究竟是由视网膜单独负责还是同时涉及了视网膜和脑皮层，这个问题争论不止。通过分离视网膜反弹信号(retinalrebound response)，研究者认为尽管大脑皮层可以调节视觉后像，但其产生仅由视网膜负责。本研究采用反证法反驳了这一假设，证明脑皮层直接参与了视觉后像的产生。实验中在每只眼中呈现2×2 的垂直和水平光栅，并且让双眼中的光栅相互垂直，可以产生从单眼模式到双眼模式的知觉状态。由于适应，面对同样对比度的刺激，视觉系统在诱导阶段的敏感性低于后像阶段，那么后像刺激的对比度要更强才能与诱导阶段刺激诱发同等强度的知觉状态。由于单眼模式随着对比度的增强而逐渐增多，那么可以推知后像刺激的单眼模式应该远远大于诱导阶段。但是，被试却知觉到了大量的双眼模式图像。更重要的是，这种现象不是由对比度降低、图像模糊而引起，且不受到颜色和相位极性的影响，诱导阶段的微眼动也不能解释这一现象。基于此，本研究反驳了视网膜单独负责后像产生的观点，证明大脑皮层直接参与了视觉后像的形成，而不仅仅是调节。同时，研究证明离眼适应后形成的视觉后像具有很强的整合倾向，这种倾向可能是人类视觉系统的固有属性。

Whether retinal process alone or retinal and cortical processes jointly determine afterimage (AI) formation has long been debated. By disclosing the retinal rebound responses, recent work proposes that afterimage signals are exclusively generated in the retina, although later modified by cortical mechanisms. We tested this notion with the method of “indirect proof”. Each eye was presented with a 2-by-2 checkerboard of horizontal and vertical grating patches. Each corresponding patch of the two checkerboards was perpendicular to each other, which produces binocular rivalry, and can generate percepts ranging from complete interocular grouping to either monocular pattern. The monocular percepts became more frequent with higher contrast. Due to adaptation, the visual system is less sensitive during the AIs than during the inductions with AI-similar contrast. If the retina is the only origin of AIs, comparable contrast appearance would require stronger retinal signals in the AIs than in the inductions, thus leading to more frequent monocular percepts in the AIs than in the inductions. Surprisingly, subjects saw the fully coherent stripes significantly more often in AIs. Our results thus contradict the retinal generation notion, and suggest that in addition to the retina, cortex is directly involved in the generation of AI signals. Our findings suggest that AI formation after binocular rivalry adaptation is strongly dominated by mechanisms favoring pattern coherency, which may be an intrinsic preference of the visual system.