Function of Fixational Instability During Natural Viewing

描述（由申请人提供）：我们的眼睛从不休息，即使专注于一个点。我们通常没有意识到，在注视的过程中，微小的眼球运动不断地改变视网膜上的刺激。当刺激物被人为地固定在视网膜上时，视觉感知往往会消退，长期以来人们一直假设眼睛的持续注视运动在视觉感知中起着根本作用。我们最近由美国国立卫生研究院资助的几项研究结果表明，事实上，这种运动是主动感觉运动策略的关键计算元素，视觉系统通过这种策略在时间域处理空间信息。以我们最近的研究结果为基础，这个项目研究了使用眼球运动来代表时空的感知、计算和神经后果。它解决了三个基本问题：（目标1）空间信息是如何在由注视眼运动引起的亮度调制中编码的？（目标2）如何提取和解释这些信息？（Aim 3）输入能量的时空再分配是否可以通过控制注视眼动来根据任务进行调整？为了将注视眼动的知觉影响与其对视觉信息的神经编码的影响联系起来，并阐明编码/解码机制，本项目将人类视觉心理物理学、视网膜输入的统计和计算分析以及神经建模结合起来。实验将关键地使用一个复杂的系统，用于注视随性显示（已经开发和广泛测试），它允许精确，但高度灵活的控制视网膜刺激。统计、计算和建模研究将重建和检查视网膜受体所经历的视觉输入信号，并模拟视网膜和外侧膝状核中的神经元反应。视觉系统使用行为通过时间来表示空间的观点在最基本的层面上挑战了当前对早期视觉处理机制的看法：它取代了视网膜作为优化整体信息传输的被动编码阶段的传统观念，取而代之的是一个主动的、可调的特征提取系统，其功能只能与眼球运动一起理解。这种视角的转变表明，眼球运动在一定程度上决定了空间视觉的基本特性（例如，对比敏感度及其动态），而这些特性目前仅被归因于神经机制。了解固定不稳定的功能影响也可能导致新的治疗方法在许多疾病的视觉障碍，其表现包括异常的固定眼运动。

DESCRIPTION (provided by applicant): Our eyes are never at rest, even when attending to a single point. We are normally not aware that, in the periods of fixation, microscopic eye movements continually shift the stimulus on the retina. Visual percepts tend to fade when the stimulus is artificially immobilized on the retina, and it has long been hypothesized that the incessant fixational motion of the eye plays a fundamental role in visual perception. Several findings from our recent NIH-funded research suggest that this motion is, in fact, a critical computational element of an active sensorimotor strategy by which the visual system processes spatial information in the temporal domain. Building upon our recent results, this project examines the perceptual, computational, and neural consequences of using eye movements to represent space through time. It addresses three fundamental questions: (Aim 1) How is spatial information encoded in the modulations of luminance resulting from fixational eye movements? (Aim 2) How is this information extracted and interpreted? (Aim 3) Can the spatiotemporal redistribution of input energy be adjusted according to task by controlling fixational eye movements? To link the perceptual influences of fixational eye movements to their effect on the neural coding of visual information and elucidate encoding/decoding mechanisms, this project integrates visual psychophysics in humans, statistical and computational analysis of retinal input, and neural modeling. Experiments will make critical use of a sophisticated system for gaze-contingent display (already developed and extensively tested), which allows precise, yet highly flexible control of retinal stimulation. Statistical, computational, and modeling studies wil reconstruct and examine the visual input signals experienced by retinal receptors and simulate neuronal responses in the retina and lateral geniculate nucleus. The proposal that the visual system uses behavior to represent space through time challenges current views on the mechanisms of early visual processing at the most fundamental level: it replaces the traditional notion of the retina as a passive encoding stage that optimizes overall information transmission with that of an active, tunable system for feature extraction, whose function can only be understood in conjunction with eye movements. This shift of view implies that eye movements are in part responsible for fundamental properties of spatial vision (e.g., contrast sensitivity an its dynamics) that, at present, are solely attributed to neural mechanisms. Understanding the functional implications of fixational instability may also lead to new treatment approaches for visual impairments in the many disordrs whose manifestations include abnormal fixational eye movements.