Yedutenko Matthew, Howlett Marcus H C, Kamermans Maarten
Retinal Signal Processing Lab, Netherlands Institute for Neuroscience, Amsterdam, Netherlands.
Department of Biomedical Physics and Biomedical Optics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands.
Front Cell Neurosci. 2021 Jan 15;14:595193. doi: 10.3389/fncel.2020.595193. eCollection 2020.
The goal of sensory processing is to represent the environment of an animal. All sensory systems share a similar constraint: they need to encode a wide range of stimulus magnitudes within their narrow neuronal response range. The most efficient way, exploited by even the simplest nervous systems, is to encode relative changes in stimulus magnitude rather than the absolute magnitudes. For instance, the retina encodes contrast, which are the variations of light intensity occurring in time and in space. From this perspective, it is easy to understand why the bright plumage of a moving bird gains a lot of attention, while an octopus remains motionless and mimics its surroundings for concealment. Stronger contrasts simply cause stronger visual signals. However, the gains in retinal performance associated with higher contrast are far more than what can be attributed to just a trivial linear increase in signal strength. Here we discuss how this improvement in performance is reflected throughout different parts of the neural circuitry, within its neural code and how high contrast activates many non-linear mechanisms to unlock several sophisticated retinal computations that are virtually impossible in low contrast conditions.
感觉处理的目标是呈现动物所处的环境。所有感觉系统都有一个相似的限制：它们需要在其狭窄的神经元反应范围内编码广泛的刺激强度。即使是最简单的神经系统也采用的最有效方法，是编码刺激强度的相对变化而非绝对强度。例如，视网膜编码对比度，即光强度在时间和空间上的变化。从这个角度来看，很容易理解为什么一只移动的鸟鲜艳的羽毛会吸引很多注意，而章鱼却保持不动并模仿周围环境以进行伪装。更强的对比度 simply 会产生更强的视觉信号。然而，与更高对比度相关的视网膜性能提升远不止于仅仅由信号强度的简单线性增加所导致的。在这里，我们将讨论这种性能提升如何在神经回路的不同部分、其神经编码中得到体现，以及高对比度如何激活许多非线性机制来解锁一些在低对比度条件下几乎不可能实现的复杂视网膜计算。
