CONVERGENCE AND DIVERGENCE OF CONES ONTO BIPOLAR CELLS IN THE CENTRAL AREA OF CAT RETINA
CONVERGENCE AND DIVERGENCE OF CONES ONTO BIPOLAR CELLS IN THE CENTRAL AREA OF CAT RETINA
复制标题
DOI：
10.1098/rstb.1990.0202
复制
发表时间：
1990-12-29
影响因子：
6.3
通讯作者：
STERLING, P
中科院分区：
文献类型：
--
作者：
COHEN, E;STERLING, P
在猫视网膜中央区，支配内丛状层亚板层B的锥体双极细胞有五种类型，其中四种具有窄的树突野，一种具有宽的树突野。这在前一篇论文（Cohen & Sterling 1990 a）中通过连续切片的电子显微照片重建得到了证明。在这里，我们通过对相同材料的进一步分析表明，对于每种窄视野类型（b1，b2和b4），覆盖因子（树突状扩散x细胞密度）约为1。对于另一种窄场型（b3），情况可能也是如此，但这无法证明，因为它的树突太细而无法追踪。B1、B2和B4型树突从其所及范围内的所有锥状蒂收集，并且不绕过局部蒂而有利于更远的蒂。b5型树突，宽视野细胞，绕过许多蒂。平均5.1 +/- 1.0个椎弓根会聚在b1双极细胞上; 6.0 +/- 1.2个椎弓根会聚在b2细胞上，5.7 +/- 1.5个椎弓根会聚在b4细胞上。一个类型内的分歧是最小的：一个蒂接触只有1.2 b1细胞，1.0 b2细胞，和1.0 b4细胞。不同类型的分歧是广泛的：每个椎弓根显然接触所有四种类型的窄场双极细胞，支配亚板B。每个椎弓根可能还与另外4-5种支配亚板的窄视野双极细胞相接触。将视锥信号编码到多个平行的窄场路径中有几个可能的优点。其中包括：调谐传输不同时间频率的通路，使用具有广泛分离的平衡电位的离子通道（以增加增益），以及在内部丛状层中形成不同的调节回路。后一种可能性将允许在视觉信号朝向不同类型的神经节细胞的途中对视觉信号执行不同的操作（例如线性或非线性）。
In the central area of cat retina the cone bipolar cells that innervate sublamina b of the inner plexiform layer comprise five types, four with narrow dendritic fields and one with a wide dendritic field. This was shown in the preceding paper (Cohen & Sterling 1990 a) by reconstruction from electron micrographs of serial sections. Here we show by further analysis of the same material that the coverage factor (dendritic spread x cell density) is about one for each of the narrow-field types (b1, b2, and b4). The same is probably true for the other narrow-field type (b3), but this could not be proved because its dendrites were too fine to trace. The dendrites of types b1, b2, and b4 collect from all the cone pedicles within their reach and do not bypass local pedicles in favour of more distant ones. The dendrites of type b5, the wide-field cell, bypass many pedicles. On average 5.1 +/- 1.0 pedicles converge on a b1 bipolar cell; 6.0 +/- 1.2 converge on a b2 cell and 5.7 +/- 1.5 converge on a b4 cell. Divergence within a type is minimal: one pedicle contacts only 1.2 b1 cells, 1.0 b2 cells, and 1.0 b4 cells. Divergence across types is broad: each pedicle apparently contacts all four types of the narrow-field bipolar cells that innervate sublamina b. Each pedicle probably also contacts an additional 4-5 types of narrow-field bipolar cell that innervate sublamina a. There are several possible advantages to encoding the cone signal into multiple, parallel, narrow-field pathways. These include: tuning of pathways to transmit different temporal frequencies, use of ion channels with widely separated equilibrium potentials (to increase gain), and formation of different regulatory circuits in the inner plexiform layer. The latter possibility would permit different operations (e.g. linear or nonlinear) to be performed on the visual signal on its way towards different types of ganglion cell.