Meister M
Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 1996 Jan 23;93(2):609-14. doi: 10.1073/pnas.93.2.609.
The visual world is presented to the brain through patterns of action potentials in the population of optic nerve fibers. Single-neuron recordings show that each retinal ganglion cell has a spatially restricted receptive field, a limited integration time, and a characteristic spectral sensitivity. Collectively, these response properties define the visual message conveyed by that neuron's action potentials. Since the size of the optic nerve is strictly constrained, one expects the retina to generate a highly efficient representation of the visual scene. By contrast, the receptive fields of nearby ganglion cells often overlap, suggesting great redundancy among the retinal output signals. Recent multineuron recordings may help resolve this paradox. They reveal concerted firing patterns among ganglion cells, in which small groups of nearby neurons fire synchronously with delays of only a few milliseconds. As there are many more such firing patterns than ganglion cells, such a distributed code might allow the retina to compress a large number of distinct visual messages into a small number of optic nerve fibers. This paper will review the evidence for a distributed coding scheme in the retinal output. The performance limits of such codes are analyzed with simple examples, illustrating that they allow a powerful trade-off between spatial and temporal resolution.
视觉世界通过视神经纤维群体中的动作电位模式呈现给大脑。单神经元记录表明，每个视网膜神经节细胞都有一个空间受限的感受野、有限的整合时间和特定的光谱敏感性。总体而言，这些反应特性定义了该神经元动作电位所传达的视觉信息。由于视神经的大小受到严格限制，人们期望视网膜能生成视觉场景的高效表征。相比之下，附近神经节细胞的感受野常常重叠，这表明视网膜输出信号之间存在大量冗余。最近的多神经元记录可能有助于解决这一矛盾。这些记录揭示了神经节细胞之间的协同放电模式，即一小群附近的神经元以仅几毫秒的延迟同步放电。由于这种放电模式的数量比神经节细胞的数量多得多，这样一种分布式编码可能使视网膜能够将大量不同的视觉信息压缩到少数视神经纤维中。本文将综述视网膜输出中分布式编码方案的证据。通过简单的例子分析了此类编码的性能极限，表明它们允许在空间和时间分辨率之间进行有力的权衡。
