Linearity and Non-linearity in the Retinal Light Response

这项为期三年的持续资助是关于视觉机制的。 眼睛里的反应。 眼睛的视网膜是感觉组织 含有与多种细胞相连的感光细胞 神经细胞 人类视觉处理的最简单的亚单位是 当它被照射时，来自视网膜的均匀斑块的反应 受到光的刺激。 这种对光的反应并不简单， 受到一系列事件的影响， 线性和非线性过程。 在过去的世纪， 心理物理学“定律”已经建立， 对刺激的反应会随着时间而改变。 但其中一些定律意味着 简单的线性增加刺激效应，有些人暗示， 效果不能线性相加。 这个项目将试图澄清什么样的处理， 视网膜在非极端条件下可以满足所有这些定律 条件 在每种情况下响应的线性问题 视觉系统的水平，以及 线性失效具有补充意义， 视觉处理的顺序。 一般的做法是 使用非线性阶段作为标记来确定响应 在每个这样的标记之前和之后的动态。 人类观察者将 通过测量他们对 闪烁的灯光，而不同的强度和持续时间， 刺激计划 第一组实验将检查 光转导机制的线性，其中 首先将光信号转换为神经响应信号。 将使用高到足以使系统饱和的强度水平 探索光化学反应的时间进程， 饱和度。 第二个实验将测试非- 线性适用于感知阈值的变化， 当光有大的突然“阶跃”变化时的测试脉冲 强度。 数据分析将包括数学 描述刺激反应的函数模型 关系。 这种综合方法是一种新颖的、非常复杂的 一个是具有很强的理论性。 结果应 对许多领域的视觉研究产生了影响， 其他系统中的信息处理。

This continuing grant for three years is on mechanisms of visual response in the eye. The retina of the eye is the sensory tissue containing the photoreceptor cells connected to several kinds of nerve cells. The simplest subunit of human visual processing is the response from a uniform patch of retina illuminated when it is stimulated by light. This response to light is not simple, but subject to a sequence of events which can be modelled mathematically as linear and non-linear processes. Over the past century, a set of psychophysical "laws" have been established to relate dynamic visual responses to stimulus changes over time. But some of these laws imply simple linear addition of stimulus effects, and some imply that the effects cannot be added linearly. This project will try to clarify what kinds of processing in the retina could satisfy all of these laws under non-extreme conditions. The question of linearity of the response at each level of the visual system, and conditions under which the linearity fails have complementary significance un unravelling the sequence of visual processing. The general approach is to use the nonlinear stages as markers to determine the response dynamics before and after each such marker. Human observers will be tested by measuring their perception of the intensity of flickering lights, while varying the intensity and duration of the stimulus. The first set of experiments will examine the linearity of the mechanism of phototransduction, in which the light signal is first converted to a neural response signal. intensity levels high enough to saturate the system will be used to explore the time course of photochemical reactions preceding the saturation. The second experiments will test how non- linearity applies to the change in threshold for perception of a test pulse when there is a large abrupt "step" change in light intensity. Analysis of the data will include mathematical modelling of the functions describing the stimulus-response relationships. This integrated approach is a novel and very sophisticated one, with a strong theoretical component. The results should have impact on visual research in many areas, and on models of information processing in other systems.