Contrast enhancement and distributed encoding by bipolar cells in the retina
Contrast enhancement and distributed encoding by bipolar cells in the retina
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DOI：
10.1152/jn.1998.80.3.1070
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发表时间：
1998-09-01
影响因子：
2.5
通讯作者：
Fahey, PK
中科院分区：
文献类型：
--
作者：
Burkhardt, DA;Fahey, PK
双极细胞，视锥光感受器，水平细胞的反应记录在细胞内灌流眼杯准备的虎蝾螈（Ambystoma tigrinum）。在感受野的中心施加正极性和负极性的对比散列，同时整个视网膜适应20 cd/m2的背景场。对于小的对比度，许多双极细胞显示出非常高的对比度增益：高达15-20%的双极反应是由1%的对比度阶跃引起的。有相当大的变化，从细胞到细胞，但平均而言，没有显着差异的对比度增益之间发现去极化（Bd）和超极化（Bh）双极细胞。锥光感受器和锥驱动双极的对比度/响应测量的定量比较表明，双极的高对比度增益是跨越锥->双极突触的小信号放大5-10倍的结果。双极细胞有一个非常有限的线性范围内的反应，并趋于饱和，在刺激水平内的线性范围内的锥响应;水平细胞的对比度/响应是类似的锥和显着不同的Bh细胞。对于相同对比度的步骤，无论对比度大小如何，Bh细胞的潜伏期都比艾德细胞的潜伏期短20 ms。对于双极细胞和视锥细胞，对比度极性对潜伏期的影响似乎主要是由于光阶的绝对值，在。在大信号域中，双极细胞的对比度响应的属性明显不同，无论是在艾德和Bh类之间。这两类细胞都可以是正对比或负对比占优势的。这些和其他结果表明，在光适应视网膜，双极人口是功能多样的，并有可能提供一个丰富的基板分布式编码的视觉图像。
Responses of bipolar cells, cone photoreceptors, and horizontal cells were recorded intracellularly in superfused eyecup preparations of the tiger salamander (Ambystoma tigrinum). Contrast hashes of positive and negative polarity were applied at the center of the receptive field while the entire retina was light adapted to a background field of 20 cd/m(2). For small contrasts, many bipolar cells showed remarkably high contrast gain: up to 15-20% of the bipolar response was evoked by a contrast step of 1%. There was considerable variation from cell to cell but, on average, no striking differences in contrast gain were found between the depolarizing (Bd) and hyperpolarizing (Bh) bipolar cells. Quantitative comparisons of contrast/response measurements for cone photoreceptors and cone-driven bipolars suggest that the high contrast gain of bipolars is the consequence of a 5-10 x amplification of small signals across the cone -->, bipolar synapse. Bipolar cells had a very restricted linear range of response and tended to saturate at stimulus levels that were within the linear range of the cone response;The contrast/response of horizontal cells was similar to that of cones and differed markedly from that of Bh cells. For steps of equal contrast, the latency of the Bh cells was similar to 20 ms shorter than that of the Ed cells regardless of the contrast magnitude. For both bipolar cells and cones; the effect of contrast polarity on latency seems largely due to the absolute value of the light step, at. In the large signal domain, properties of the contrast responses of bipolar cells varied appreciably, both within and between the Ed and Bh classes. Cells of either class could be positive- or negative-contrast dominant. These and additional results show that in the light-adapted retina, the bipolar population is functionally diverse and has the potential to provide a rich substrate for distributed encoding of visual images.