Perturbing gaze shifts reveals new visuo-motor encoding mechanisms

扰动的目光转移揭示了新的视觉运动编码机制

• 批准号: RGPIN-2016-04189
• 负责人: Guitton, Daniel
• 金额: $ 2.55万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709042
• 关键词: Perturbing; gaze; shifts; reveals; new

Humans are skilled at making rapid, accurate movements that involve functionally coupled body segments that move simultaneously. How the brain orchestrates such complex movements has been a major focus of my lab and, as an experimental model, we have studied coordinated eye + head movements that routinely generate rapid orienting movements of the visual axis called gaze saccades. The midbrain's superior colliculus (SC) is a critical structure in gaze control. The classic hypothesis is that the SC contains a motor map which drives rapid (saccadic) gaze shifts according to a coding scheme wherein one-site on the map encodes one gaze shift vector. We call this the “one-site, one- saccade” hypothesis. We have preliminary evidence that this hypothesis fails when one looks about the environment using a sequence of rapid gaze saccades separated by periods of fixation. In this context the SC encodes the overall displacement not individual saccades. This critical break with the dominant hypothesis of SC function needs to be verified which we propose to do here. If we confirm failure then this will call for a critical re-evaluation of current models of how the brain controls how we look about the environment. The objective of looking about the environment is obviously to see'. This simple day to day term hides an extraordinarily complex ensemble of brain functions that underlie perception. For one thing we need to link vision with movements of the eyes. Such a link is necessary because: 1) our visual world appears stable across saccadic gaze shifts despite a perceived object changing position on the retina as we make saccades 3-5 times/sec; and 2) a spatially-fixed locus of attention occupies a different position on the retina after each saccade but must internally be perceived as spatially immobile. Interestingly, the brain's visual system is organized in visual maps in a manner analogous to the SC's motor map. Thus, one site on a visual map encodes one small location in visual space. This is called the “one-site, one-receptive-field” hypothesis. Similar to the gaze motor system there is evidence that this hypothesis can fail. Indeed, a neuron in a visual map can respond to a visual stimulus presented anywhere in the visual world depending on the direction and amplitude of the upcoming saccade. Thus one site on a visual map can encode an infinite number of spatial positions! This radical break with classic thinking needs to be understood to understand vision. We plan to do this here by studying how visual neurons respond to visual stimuli when the intended gaze saccade is perturbed. Together, the key principles of brain organization in the motor and visual system can be referred to as the “one-site, one-function” hypotheses. We have models of how these systems work but when they don't work, it is critical to understand why if we are to understand brain function and how we see when we scan our environment.

人类擅长做出快速、准确的运动，这些运动涉及同时运动的功能耦合的身体部位。 大脑如何协调如此复杂的运动一直是我实验室的主要焦点，作为一个实验模型，我们研究了协调的眼睛+头部运动，这些运动通常会产生视轴的快速定向运动，称为注视扫视。 中脑的上丘（SC）是凝视控制的关键结构。经典的假设是，SC 包含一个运动图，该运动图根据一种编码方案驱动快速（扫视）注视移动，其中图上的一个位点编码一个注视移动矢量。我们称之为“单点、单次扫视”假说。我们有初步证据表明，当一个人使用一系列由注视时间间隔的快速目光扫视来观察环境时，这一假设就会失败。在这种情况下，SC 编码整体位移而不是单个扫视。这种与 SC 功能的主导假设的重大突破需要得到验证，我们建议在此进行验证。如果我们确认失败，那么这将需要对大脑如何控制我们对环境的看法的当前模型进行批判性的重新评估。 观察环境的目的显然是为了“看”。这个简单的日常术语隐藏着感知基础上极其复杂的大脑功能整体。一方面，我们需要将视觉与眼睛的运动联系起来。这种联系是必要的，因为：1）尽管当我们每秒扫视 3-5 次时，感知到的物体会改变视网膜上的位置，但我们的视觉世界在扫视注视变化时显得稳定； 2）每次眼跳后，空间固定的注意力焦点在视网膜上占据不同的位置，但必须在内部被感知为空间固定的。 有趣的是，大脑的视觉系统以类似于 SC 运动图的方式组织在视觉图中。因此，视觉地图上的一个站点编码视觉空间中的一个小位置。这称为“单位点、单感受野”假说。与凝视运动系统类似，有证据表明这一假设可能会失败。事实上，视觉图中的神经元可以根据即将到来的眼跳的方向和幅度对视觉世界中任何地方呈现的视觉刺激做出反应。因此，视觉地图上的一个站点可以编码无限数量的空间位置！为了理解视觉，需要理解这种与经典思维的彻底决裂。我们计划通过研究当预期的目光扫视受到干扰时视觉神经元如何对视觉刺激做出反应来做到这一点。 总之，运动和视觉系统中大脑组织的关键原则可以称为“单一部位、单一功能”假设。我们有这些系统如何工作的模型，但当它们不起作用时，如果我们要了解大脑功能以及我们在扫描环境时如何看到，那么了解其原因至关重要。