Werner Reichardt Centre for Integrative Neurosciences (CIN)/Institute for Ophthalmic Research, University of Tübingen, Otfried-Müller-Strasse 25, 72076 Tübingen, Germany; Bernstein Centre for Computational Neuroscience (BCCN), University of Tübingen, Otfried-Müller-Strasse 25, 72076 Tübingen, Germany.
Neuron. 2013 Dec 4;80(5):1206-17. doi: 10.1016/j.neuron.2013.09.030.
For efficient coding, sensory systems need to adapt to the distribution of signals to which they are exposed. In vision, natural scenes above and below the horizon differ in the distribution of chromatic and achromatic features. Consequently, many species differentially sample light in the sky and on the ground using an asymmetric retinal arrangement of short- (S, "blue") and medium- (M, "green") wavelength-sensitive photoreceptor types. Here, we show that in mice this photoreceptor arrangement provides for near-optimal sampling of natural achromatic contrasts. Two-photon population imaging of light-driven calcium signals in the synaptic terminals of cone-photoreceptors expressing a calcium biosensor revealed that S, but not M cones, preferred dark over bright stimuli, in agreement with the predominance of dark contrasts in the sky but not on the ground. Therefore, the different cone types do not only form the basis of "color vision," but in addition represent distinct (achromatic) contrast-selective channels.
为了实现高效编码，感觉系统需要适应它们所暴露的信号分布。在视觉中，地平线以上和以下的自然场景在颜色和非颜色特征的分布上存在差异。因此，许多物种使用短波长（S，“蓝色”）和中波长（M，“绿色”）感光体类型的不对称视网膜排列，对天空和地面的光进行不同的采样。在这里，我们表明，在老鼠中，这种感光体排列提供了对自然非颜色对比度的近乎最佳采样。使用钙生物传感器表达钙驱动钙信号的双光子群体成像显示，S 锥而不是 M 锥更喜欢暗于亮的刺激，这与天空中暗对比的优势一致，但与地面上的暗对比不一致。因此，不同的锥体细胞不仅构成了“颜色视觉”的基础，而且还代表了不同的（非颜色）对比选择性通道。
