Wagner H, Frost B
Department of Psychology, Queen's University, Kingston, Canada.
Nature. 1993 Aug 26;364(6440):796-8. doi: 10.1038/364796a0.
We experience the visual world as being three-dimensional. A major source of depth information derives from the slightly different views of each eye, leading to small variations in the retinal images ('disparities'). Neurons sensitive to visual disparities are thought to form the neural basis of stereo vision. Barn owls as well as several mammalian species have neurons that are sensitive to visual disparities. But how visual disparities are represented in the brain has been a matter of discussion ever since the first disparity-sensitive neurons were found some 25 years ago. Here we adopt a new approach to this problem and study the neural computation of visual disparities with a paradigm borrowed from auditory research. The measurement of interaural time difference (ITD) has many similarities with the measurement of visual disparity on the formal, algorithmic level. We speculate that the similarities might extend to the level of neural computation. The neural representation of ITD is well understood, and we have studied the representation of disparities with visual stimuli analogous to those successfully used in acoustic experiments. For example, ITD is converted in the brain to a pathlength on an axon that, owing to the finite conduction velocity in neurons, exactly matches the external ITD. This pathlength is called 'characteristic delay'. Our results suggest that there is an analogue of the characteristic delay in stereo vision which we propose to call 'characteristic disparity'.
我们所体验到的视觉世界是三维的。深度信息的一个主要来源是每只眼睛略有不同的视角，这导致视网膜图像出现微小差异（“视差”）。对视觉视差敏感的神经元被认为构成了立体视觉的神经基础。仓鸮以及几种哺乳动物都有对视觉视差敏感的神经元。但是，自从大约25年前首次发现视差敏感神经元以来，视差在大脑中是如何被表征的一直是一个有争议的问题。在这里，我们采用一种新方法来解决这个问题，并借鉴听觉研究中的一个范式来研究视觉视差的神经计算。双耳时间差（ITD）的测量在形式和算法层面上与视觉视差的测量有许多相似之处。我们推测这些相似性可能会延伸到神经计算层面。ITD的神经表征已得到充分理解，并且我们已经用类似于在声学实验中成功使用的视觉刺激来研究视差的表征。例如，ITD在大脑中被转换为轴突上的路径长度，由于神经元中的有限传导速度，该路径长度与外部ITD精确匹配。这个路径长度被称为“特征延迟”。我们的结果表明，在立体视觉中存在特征延迟的类似物，我们提议将其称为“特征视差”。
