Curcio C A, Allen K A
Department of Biological Structure, University of Washington, Seattle 98195.
J Comp Neurol. 1990 Oct 1;300(1):5-25. doi: 10.1002/cne.903000103.
We quantified the spatial distribution of presumed ganglion cells and displaced amacrine cells in unstained whole mounts of six young normal human retinas whose photoreceptor distributions had previously been characterized. Cells with large somata compared to their nuclei were considered ganglion cells; cells with small somata relative to their nuclei were considered displaced amacrine cells. Within the central area, ganglion cell densities reach 32,000-38,000 cells/mm2 in a horizontally oriented elliptical ring 0.4-2.0 mm from the foveal center. In peripheral retina, densities in nasal retina exceed those at corresponding eccentricities in temporal retina by more than 300%; superior exceeds inferior by 60%. Displaced amacrine cells represented 3% of the total cells in central retina and nearly 80% in the far periphery. A twofold range in the total number of ganglion cells (0.7 to 1.5 million) was largely explained by a similar range in ganglion cell density in different eyes. Cone and ganglion cell number were not correlated, and the overall cone:ganglion cell ratio ranged from 2.9 to 7.5 in different eyes. Peripheral cones and ganglion cells have different topographies, thus suggesting meridianal differences in convergence onto individual ganglion cells. Low convergence of foveal cones onto individual ganglion cells is an important mechanism for preserving high resolution at later stages of neural processing. Our improved estimates for the density of central ganglion cells allowed us to ask whether there are enough ganglion cells for each cone at the foveal center to have a direct line to the brain. Our calculations indicate that 1) there are so many ganglion cells relative to cones that a ratio of only one ganglion cell per foveal cone would require fibers of Henle radiating toward rather than away from the foveal center; and 2) like the macaque, the human retina may have enough ganglion cells to transmit the information afforded by closely spaced foveal cones to both ON- and OFF-channels. Comparison of ganglion cell topography with the visual field representation in V1 reveals similarities consistent with the idea that cortical magnification is proportional to ganglion cell density throughout the visual field.
我们对6只年轻正常人类视网膜的未染色整装标本中假定的神经节细胞和移位无长突细胞的空间分布进行了量化，这些视网膜的光感受器分布此前已被表征。与细胞核相比，胞体较大的细胞被视为神经节细胞；相对于细胞核，胞体较小的细胞被视为移位无长突细胞。在中心区域，神经节细胞密度在距中央凹中心0.4 - 2.0毫米的水平椭圆形环内达到32,000 - 38,000个细胞/平方毫米。在周边视网膜中，鼻侧视网膜的密度比颞侧视网膜相应偏心度处的密度高出300%以上；上方密度比下方高出60%。移位无长突细胞在中央视网膜中占细胞总数的3%，在最周边区域接近80%。神经节细胞总数的两倍范围（0.7至150万）很大程度上是由不同眼睛中神经节细胞密度的类似范围所解释。视锥细胞和神经节细胞数量不相关，不同眼睛中视锥细胞与神经节细胞的总体比例在2.9至7.5之间。周边视锥细胞和神经节细胞具有不同的拓扑结构，因此表明在向单个神经节细胞汇聚方面存在子午线差异。中央凹视锥细胞向单个神经节细胞的低汇聚是在神经处理后期保持高分辨率的重要机制。我们对中央神经节细胞密度的改进估计使我们能够询问在中央凹中心是否有足够的神经节细胞让每个视锥细胞都能直接与大脑建立联系。我们的计算表明：1）相对于视锥细胞，神经节细胞数量如此之多，以至于每个中央凹视锥细胞只有一个神经节细胞的比例将需要亨勒纤维向中央凹中心而非远离中央凹中心辐射；2）与猕猴一样，人类视网膜可能有足够的神经节细胞将紧密排列的中央凹视锥细胞提供的信息传递到ON和OFF通道。将神经节细胞拓扑结构与V1中的视野表征进行比较，发现了一些相似之处，这与整个视野中皮质放大率与神经节细胞密度成正比的观点一致。
