Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 2012 Sep 4;109(36):E2391-8. doi: 10.1073/pnas.1211547109. Epub 2012 Aug 13.
The retina reports the visual scene to the brain through many parallel channels, each carried by a distinct population of retinal ganglion cells. Among these, the population with the smallest and densest receptive fields encodes the neural image with highest resolution. In human retina, and those of cat and macaque, these high-resolution ganglion cells act as generic pixel encoders: They serve to represent many different visual inputs and convey a neural image of the scene downstream for further processing. Here we identify and analyze high-resolution ganglion cells in the mouse retina, using a transgenic line in which these cells, called "W3", are labeled fluorescently. Counter to the expectation, these ganglion cells do not participate in encoding generic visual scenes, but remain silent during most common visual stimuli. A detailed study of their response properties showed that W3 cells pool rectified excitation from both On and Off bipolar cells, which makes them sensitive to local motion. However, they also receive unusually strong lateral inhibition, both pre- and postsynaptically, triggered by distant motion. As a result, the W3 cell can detect small moving objects down to the receptive field size of bipolar cells, but only if the background is featureless or stationary--an unusual condition. A survey of naturalistic stimuli shows that W3 cells may serve as alarm neurons for overhead predators.
视网膜通过许多平行的通道向大脑报告视觉场景，每个通道都由特定的视网膜神经节细胞群体携带。在这些细胞中，具有最小和最密集感受野的群体以最高分辨率对神经图像进行编码。在人类视网膜、猫和猕猴的视网膜中，这些高分辨率的神经节细胞充当通用像素编码器：它们用于表示许多不同的视觉输入，并将场景的神经图像传递到下游进行进一步处理。在这里，我们使用一种转基因系来鉴定和分析小鼠视网膜中的高分辨率神经节细胞，这些细胞被称为“W3”，用荧光标记。与预期相反，这些神经节细胞并不参与通用视觉场景的编码，而是在大多数常见的视觉刺激下保持沉默。对其反应特性的详细研究表明，W3 细胞从 On 和 Off 双极细胞中汇集整流的兴奋，这使它们对局部运动敏感。然而，它们也受到异常强烈的前突触和后突触侧抑制，这是由远距离运动触发的。因此，W3 细胞可以检测到小到双极细胞感受野大小的运动物体，但前提是背景是无特征的或静止的——这是一种不寻常的情况。对自然刺激的调查表明，W3 细胞可能作为头顶捕食者的警报神经元。
