Center/surround organization of retinal bipolar cells: High correlation of fundamental responses of center and surround to sinusoidal contrasts
Center/surround organization of retinal bipolar cells: High correlation of fundamental responses of center and surround to sinusoidal contrasts
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DOI：
10.1017/s0952523811000071
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发表时间：
2011-05-01
影响因子：
1.9
通讯作者：
Thoreson, Wallace B.
中科院分区：
文献类型：
--
作者：
Burkhardt, Dwight A.;Bartoletti, Theodore M.;Thoreson, Wallace B.
在完整的光适应性虎蝾螈（Ambystoma tigrinum）视网膜上，用细胞内记录的方法研究了视锥细胞驱动的双极细胞的感受野组织。中心点和同心环的最佳尺寸被用来选择性地刺激感受野中心和周围的正弦调制的对比度在3赫兹。在低对比度下，ON和OFF双极细胞的中心和周围的反应都是线性的，显示出高增益，从而相对于视锥细胞的对比度增强。通过快速傅立叶变换测量的基本响应的对比度/响应曲线在13%对比度下快速达到半最大振幅，随后在高对比度下达到饱和。中心和周围响应的归一化幅度的变化非常相似，在整个响应范围内显示出具有非常高的相关性的线性回归，对于ON和OFF细胞，r（2）= 0.97。ON和OFF细胞的中心和周围的对比度/响应曲线通过单位点结合的方程很好地拟合（r（2）= 0.98）。在所研究的细胞中，约有一半细胞的中心和周围的非线性波形可以通过在时间上缩放和移动周围的响应而变得一致。这意味着在锥体反馈突触的极性反转之后，中心和周围共同的非线性发生。单锥细胞和OFF双极细胞之间的配对全细胞记录的证据表明，大量的非线性不是由于锥突触的传输，而是源于内在的双极细胞和网络机制。当正弦对比度调制同时施加到中心和周围时，在ON和OFF细胞中观察到小响应的明显加和性，而对于大响应的相互作用是惊人的非加和性。然后，周围的贡献大大减少，这表明在锥反馈突触衰减。
Receptive field organization of cone-driven bipolar cells was investigated by intracellular recording in the intact light-adapted retina of the tiger salamander (Ambystoma tigrinum). Centered spots and concentric annuli of optimum dimensions were used to selectively stimulate the receptive field center and surround with sinusoidal modulations of contrast at 3 Hz. At low contrasts, responses of both the center and surround of both ON and OFF bipolar cells were linear, showing high gain and thus contrast enhancement relative to cones. The contrast/response curves for the fundamental response, measured by a Fast Fourier Transform, reached half maximum amplitude quickly at 13% contrast followed by saturation at high contrasts. The variation of the normalized amplitude of the center and surround responses was remarkably similar, showing linear regression over the entire response range with very high correlations, r(2) = 0.97 for both ON and OFF cells. The contrast/response curves of both center and surround for both ON and OFF cells were well fit (r(2) = 0.98) by an equation for single-site binding. In about half the cells studied, the nonlinear waveforms of center and surround could be brought into coincidence by scaling and shifting the surround response in time. This implies that a nonlinearity, common to both center and surround, occurs after polarity inversion at the cone feedback synapse. Evidence from paired whole-cell recordings between single cones and OFF bipolar cells suggests that substantial nonlinearity is not due to transmission at the cone synapse but instead arises from intrinsic bipolar cell and network mechanisms. When sinusoidal contrast modulations were applied to the center and surround simultaneously, clear additivity was observed for small responses in both ON and OFF cells, whereas the interaction was strikingly nonadditive for large responses. The contribution of the surround was then greatly reduced, suggesting attenuation at the cone feedback synapse.