Receptive fields in cat visual cortex during natural locomotion

理解视觉信息在自然行为中是如何处理的是神经科学的一个基本问题。 尽管最近的研究对警觉的头部固定的主题有了深刻的见解，但在很大程度上仍然不清楚视觉处理是如何进行的。 受主动行为的影响：自我运动和主动选择视觉目标以服务于正在进行的行为。提出 这项研究旨在建立一个独特的实验范式，在自然环境中自由移动的猫的主动视觉。 运动，同时测试一个特定的假设，即视觉处理是由正在进行的行为的需要。这 新的范式建立在视觉和运动生理学的互补力量之上，并允许在 自然使用的条件：在协调和连贯的运动活动，感觉反馈，分配 注意力和动态变化的视觉输入。猫很容易走在环境中，施加不同的要求， 步进和视觉精度：从简单的平面（低要求）到在高架物体上的步进（高要求）。 使用这种强大的和重复的自然行为，我们将测量（i）视觉输入，（ii）神经元活动，（iii）行为 输出.我们将从头部固定的摄像机拍摄镜头，并记录眼睛的位置，凝视轨迹和生物力学。 头和身体。使用这些测量，我们将计算视觉输入的视网膜和身体为中心的坐标。 当猫行走时，我们将记录初级视觉（a.17和a.18）和多感觉顶叶（a.5b）神经元的活动。 皮质区我们将使用反向相关来重建视网膜定位和身体中心神经元的感受野 坐标为了测量行为输出，我们将使用最先进的头部生物力学三维分析， 身体和四肢，以及步伐的准确性。为了确定运动形状视觉处理的需要，我们将使用 对步进精度和视觉信息有不同要求的环境：从低要求（在平地上行走 表面）到高要求（踩在高架平台上）。我们的总体假设认为， 视觉皮层是任务依赖性的：对步进精度的更高要求导致空间精度的增加 视觉系统中的表现。我们的具体目标是了解运动任务的需求如何塑造视觉输入 和视觉信息的处理。我们假设，对视觉信息的精确度要求更高， 移动将通过增加视觉输入的精确度和更频繁地注视未来的脚的位置来满足 通过增加视觉反应的强度和减小 视觉感受野我们将问：（1a）由注视行为模式决定的视觉输入在 运动在不同的环境中;和（1b）如何视觉反应和感受野的变化，在运动过程中， 对视觉有不同要求的环境。获得的结果将提供（i）严格的测试和验证的新的 实验范式的研究主动视觉;和（ii）测试我们的假设，在运动过程中， 在对踏步精度要求较高、对视觉信息要求较高的环境中， 将比在低需求环境中的运动期间更强，感受野更小。这些新知识 将有助于发展新的康复策略，在运动过程中使用视觉缺陷的患者。

Understanding how visual information is processed during natural behavior is a fundamental problem of neuroscience. Despite recent insights from research in alert head-fixed subjects, it remains largely unknown how visual processing is affected by active behavior: self-motion and active selection of visual targets for serving on-going behavior. Proposed research aims to establish a unique experimental paradigm of active vision in freely moving cats during natural locomotion, while testing a specific hypothesis that visual processing is shaped by the needs of on-going behavior. This new paradigm builds on complementary strength of visual and motor physiology, and allows to study vision under conditions in which it is naturally used: during coordinated and coherent motor activity, sensory feedback, allocation of attention and dynamically changing visual input. Cats readily walk in environments that impose different demands on accuracy of stepping and vision: from simple flat surfaces (low demand) to stepping on elevated objects (high demand). Using this robust and repetitive natural behavior we will measure (i) visual input, (ii) neuronal activity, and (iii) behavioral output. We will take footage from a head-fixed camera and record the eye position, gaze trajectory, and biomechanics of head and body. Using these measurements, we will calculate visual input in retinotopic and body-centric coordinates. While cat is walking, we will record activity of neurons in primary visual (a.17 and a.18) and multisensory parietal (a.5b) cortical areas. We will use reverse-correlation to reconstruct receptive fields of neurons in retinotopic and body-centric coordinates. To measure behavioral output, we will use state-of-the-art 3-dimensional analysis of biomechanics of head, body and limbs, and the accuracy of steps. To determine how the needs of locomotion shape visual processing we will use environments with different demands on accuracy of stepping and visual information: from low demand (walking on flat surface) to high demand (stepping on elevated platforms). Our overarching hypothesis maintains that processing in visual cortex is task-dependent: higher demands on accuracy of stepping lead to an increasing precision of space representation in visual system. Our Specific Aim is to understand how demands of locomotion task shape visual input and processing of visual information. We hypothesize that higher demands on precision of visual information for locomotion will be met by increasing both precision of visual input by more frequent fixations on locations for future foot placement, and precision of visual processing by increasing the strength of visual responses and decreasing the size of visual receptive fields. We will ask: (1a) How the visual input, determined by the pattern of gaze behavior, changes during locomotion in diverse environments; and (1b) How visual responses and receptive fields change during locomotion in environments with different demands on vision. Obtained results will provide (i) rigorous testing and validation of the new experimental paradigm for research into active vision; and (ii) tests for our hypothesis, that during locomotion in environments with higher requirements on accuracy of stepping and higher demand on visual information, visual responses will be stronger and receptive fields smaller than during locomotion in low-demand environments. This new knowledge will aid the development of new rehabilitation strategies for patients with deficits in using vision during locomotion.