Graduate Program in Neurobiology and Behavior, University of Washington, Seattle, WA 98195, USA; Department of Biological Structure, University of Washington, Seattle, WA 98195, USA.
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Curr Biol. 2014 Feb 3;24(3):310-5. doi: 10.1016/j.cub.2013.12.020. Epub 2014 Jan 16.
The distributions of neurons in sensory circuits display ordered spatial patterns arranged to enhance or encode specific regions or features of the external environment. Indeed, visual space is not sampled uniformly across the vertebrate retina. Retinal ganglion cell (RGC) density increases and dendritic arbor size decreases toward retinal locations with higher sampling frequency, such as the fovea in primates and area centralis in carnivores [1]. In these locations, higher acuity at the level of individual cells is obtained because the receptive field center of a RGC corresponds approximately to the spatial extent of its dendritic arbor [2, 3]. For most species, structurally and functionally distinct RGC types appear to have similar topographies, collectively scaling their cell densities and arbor sizes toward the same retinal location [4]. Thus, visual space is represented across the retina in parallel by multiple distinct circuits [5]. In contrast, we find a population of mouse RGCs, known as alpha or alpha-like [6], that displays a nasal-to-temporal gradient in cell density, size, and receptive fields, which facilitates enhanced visual sampling in frontal visual fields. The distribution of alpha-like RGCs contrasts with other known mouse RGC types and suggests that, unlike most mammals, RGC topographies in mice are arranged to sample space differentially.
感觉回路中的神经元分布呈现有序的空间模式，这些模式被组织起来以增强或编码外部环境的特定区域或特征。事实上，脊椎动物视网膜并不是均匀地对视觉空间进行采样。视网膜神经节细胞 (RGC) 的密度在视网膜位置上增加，树突分支的大小减小，这些位置具有更高的采样频率，例如灵长类动物的中央凹和食肉动物的中央区[1]。在这些位置，由于 RGC 的感受野中心大致对应于其树突分支的空间范围，因此可以在单个细胞的水平上获得更高的分辨率[2,3]。对于大多数物种，结构和功能不同的 RGC 类型似乎具有相似的拓扑结构，它们的细胞密度和树突分支大小集体向相同的视网膜位置缩放[4]。因此，多个不同的回路以并行的方式在视网膜上表示视觉空间[5]。相比之下，我们发现了一群被称为 alpha 或 alpha-like 的小鼠 RGC，它们在细胞密度、大小和感受野方面呈现出从鼻侧到颞侧的梯度，这有助于增强对前视野的视觉采样。alpha-like RGC 的分布与其他已知的小鼠 RGC 类型形成对比，这表明与大多数哺乳动物不同，小鼠的 RGC 拓扑结构是为了以不同的方式对空间进行采样而排列的。
