Calkins D J, Schein S J, Tsukamoto Y, Sterling P
Department of Neuroscience, University of Pennsylvania, Philadelphia 19104.
Nature. 1994 Sep 1;371(6492):70-2. doi: 10.1038/371070a0.
Visual acuity depends on the fine-grained neural image set by the foveal cone mosaic. To preserve this spatial detail, cones transmit through non-divergent pathways: cone-->midget bipolar cell-->midget ganglion cell. Adequate gain must be established along each pathway; crosstalk and sources of variation between pathways must be minimized. These requirements raise fundamental questions regarding the synaptic connections: (1) how many synapses from bipolar to ganglion cell transmit a cone signal and with what degree of crosstalk between adjacent pathways; (2) how accurately these connections are reproduced across the mosaic; and (3) whether the midget circuits for middle (M) and long (L) wavelength sensitive cones are the same. We report here that the midget ganglion cell collects without crosstalk either 28 +/- 4 or 47 +/- 3 midget bipolar synapses. Two cone types are defined by this difference; being about equal in number and distributing randomly in small clusters of like type, they are probably M and L.
视力取决于由中央凹视锥细胞镶嵌所设定的精细神经图像。为了保留这种空间细节，视锥细胞通过非发散性通路进行传递：视锥细胞→侏儒双极细胞→侏儒神经节细胞。必须在每条通路上建立足够的增益；通路之间的串扰和变化源必须降至最低。这些要求引发了关于突触连接的基本问题：（1）从双极细胞到神经节细胞有多少个突触传递视锥细胞信号，相邻通路之间的串扰程度如何；（2）这些连接在整个镶嵌中复制的精确程度如何；以及（3）对中波（M）和长波（L）敏感视锥细胞的侏儒回路是否相同。我们在此报告，侏儒神经节细胞无串扰地收集28±4个或47±3个侏儒双极突触。两种视锥细胞类型由此差异定义；它们数量大致相等，在同类小簇中随机分布，可能分别是M型和L型。
