Adams Daniel L, Horton Jonathan C
Beckman Vision Center, University of California, San Francisco, San Francisco, California 94143-0730, USA.
J Neurosci. 2003 May 1;23(9):3771-89. doi: 10.1523/JNEUROSCI.23-09-03771.2003.
Shadows cast by retinal blood vessels are represented in striate cortex of the squirrel monkey. Their pattern was exploited to generate a true retinotopic map of V1. For calibration, retinal landmarks were projected onto a tangent screen to measure their visual field location. Next, the retina was warped onto striate cortex, distorting it as necessary to match each retinal vessel to its cortical representation. Maps from four hemispheres of two normal adult squirrel monkeys were created and used to derive expressions for cortical magnification factor (M). A mean map was produced by averaging the individual maps. To address the controversial issue of whether the ratio of retinal ganglion cell (RGC) density to M is constant at all eccentricities, we stained a retinal whole mount from one of the two monkeys for Nissl substance. A ganglion cell density map was compiled by sampling the concentration of cells at 171 retinal points. Allowance was made for displaced amacrine cells and for the centripetal displacement of RGCs from central photoreceptors. After these corrections the V1 surface area and RGC density were compared at each eccentricity. The cortical representation of the macula was found to be amplified, even beyond the magnification expected from its high density of RGCs. For example, the central 4 degrees of visual field were allotted 27% of the surface area of V1 but were supplied by only 12% of RGCs. We conclude that, in monkey striate cortex, more tissue is allocated per ganglion cell for the analysis of information emanating from the macula as compared with the peripheral retina.
松鼠猴纹状皮层中呈现出视网膜血管投射的阴影。利用这些阴影的模式生成了V1区的真实视网膜拓扑图。为了校准，将视网膜地标投射到切线屏上以测量其视野位置。接下来，将视网膜映射到纹状皮层上，根据需要进行变形，以使每条视网膜血管与其皮层表征相匹配。创建了来自两只正常成年松鼠猴四个半球的图谱，并用于推导皮层放大因子（M）的表达式。通过对各个图谱求平均得出平均图谱。为了解决视网膜神经节细胞（RGC）密度与M的比值在所有离心率下是否恒定这一有争议的问题，我们对两只猴子中的一只的视网膜全层进行尼氏物质染色。通过对171个视网膜点处的细胞浓度进行采样，编制了神经节细胞密度图。考虑到移位的无长突细胞以及RGC从中央感光细胞的向心移位。经过这些校正后，比较了每个离心率下V1区的表面积和RGC密度。发现黄斑的皮层表征被放大了，甚至超出了因其高密度的RGC所预期的放大倍数。例如，视野中央4度分配到了V1区表面积的27%，但仅由12%的RGC提供输入。我们得出结论，在猴纹状皮层中，与周边视网膜相比，每个神经节细胞分配了更多的组织来分析来自黄斑的信息。
