Niu Yu-Qiong, Xiao Qian, Liu Rui-Feng, Wu Le-Qing, Wang Shu-Rong
Laboratory for Visual Information Processing, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, P. R. China.
J Physiol. 2006 Dec 15;577(Pt 3):805-13. doi: 10.1113/jphysiol.2006.120071. Epub 2006 Oct 12.
Misinterpretations of visual information received by the retina are called visual illusions, which are known to occur in higher brain areas. However, whether they would be also processed in lower brain structures remains unknown, and how to explain the neuronal mechanisms underlying the motion after-effect is intensely debated. We show by extracellular recording that all motion-sensitive neurons in the pigeon's pretectum respond similarly to real and illusory contours, and their preferred directions are identical for both contours in unidirectional cells, whereas these directions are changed by 90 deg for real versus illusory contours in bidirectional cells. On the other hand, some pretectal neurons produce inhibitory (excitatory) after-responses to cessation of prolonged motion in the preferred (null) directions, whose time course is similar to that of the motion after-effect reported by humans. Because excitatory and inhibitory receptive fields of a pretectal cell overlap in visual space and possess opposite directionalities, after-responses to cessation of prolonged motion in one direction may create illusory motion in the opposite direction. It appears that illusory contours and motion could be detected at the earliest stage of central information processing and processed in bottom-up streams, and that the motion after-effect may result from functional interactions of excitatory and inhibitory receptive fields with opposite directionalities.
视网膜接收到的视觉信息的错误解读被称为视觉错觉，已知其发生在大脑更高区域。然而，它们是否也会在更低级的脑结构中被处理尚不清楚，并且如何解释运动后效背后的神经元机制也存在激烈争论。我们通过细胞外记录表明，鸽子顶盖前区所有对运动敏感的神经元对真实轮廓和虚幻轮廓的反应相似，在单向细胞中，它们对两种轮廓的偏好方向相同，而在双向细胞中，真实轮廓和虚幻轮廓的这些方向相差90度。另一方面，一些顶盖前区神经元在偏好（无效）方向上对长时间运动停止产生抑制性（兴奋性）后反应，其时间进程与人类报告的运动后效相似。由于顶盖前区细胞的兴奋性和抑制性感受野在视觉空间中重叠且具有相反的方向，对一个方向上长时间运动停止的后反应可能会在相反方向上产生虚幻运动。看来，虚幻轮廓和运动可能在中枢信息处理的最早阶段就被检测到并在自下而上的信息流中被处理，并且运动后效可能是由具有相反方向的兴奋性和抑制性感受野的功能相互作用导致的。
