Grzywacz N M, Amthor F R, Merwine D K
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115.
Vis Neurosci. 1994 Sep-Oct;11(5):1019-25. doi: 10.1017/s0952523800003953.
Biological visual systems can detect positional changes that are finer than these systems' acuity to sine-wave gratings, a property known as hyperacuity. Some systems can even detect changes finer that the photoreceptor spacing. We report here that rabbit's directionally selective ganglion cells not only detect positional changes in the hyperacuity range, but also discriminate the direction of their motion. Our experiments show that directional selectivity occurs for edges of light moving as little as 1.1 microns (26" of visual angle) across the retina. This distance corresponds to a hyperacuity, since the acuity to sine-wave gratings of rabbit's On-Off DS ganglion cells is about 125 microns (50'). In addition, this distance is smaller than the minimal spacing between rabbit photoreceptors (1.9 microns or 46"), as estimated from cell-density studies (Young & Vaney, 1991). Such a hyperacuity suggests low-noise high-gain signal transmission from photoreceptors to ganglion cells and that directional selectivity can arise in small portions of retinal dendritic processes.
生物视觉系统能够检测到比这些系统对正弦波光栅的敏锐度更精细的位置变化，这一特性被称为超敏锐度。有些系统甚至能检测到比光感受器间距更精细的变化。我们在此报告，兔子的方向选择性神经节细胞不仅能检测超敏锐度范围内的位置变化，还能辨别其运动方向。我们的实验表明，对于在视网膜上仅移动1.1微米（视角26"）的光边缘，方向选择性就会出现。这个距离对应于一种超敏锐度，因为兔子的开-关方向选择性神经节细胞对正弦波光栅的敏锐度约为125微米（50'）。此外，根据细胞密度研究（扬和瓦内，1991年）估计，这个距离小于兔子光感受器之间的最小间距（1.9微米或46"）。这种超敏锐度表明从光感受器到神经节细胞存在低噪声高增益信号传输，并且方向选择性可能出现在视网膜树突状突起的小部分区域。
