Neural Mechanisms of Visual Crowding

描述(申请人提供)：我们的目标是了解视觉拥挤的神经机制。拥挤是一种刺激相互作用现象，导致视觉模糊退化。在不移动眼睛的情况下，只有视觉场景的一小部分才能产生清晰的视觉体验。这一区域被称为功能视野。在其中，我们可以选择和仔细检查项目，识别和定义它们的特征和相互关联的部分。在它之外，我们很难对周围的物体形成鲜明而生动的印象。我们的假设是，跨越功能视野边界的过渡受视觉空间拥挤的支配。拥挤在限制中心视野丧失(如黄斑变性)患者的剩余视功能方面发挥着重要作用，因为它极大地限制了周边视野用于日常活动，如阅读。对于中央视野丧失的低视力者来说，阅读特别慢，因为近缘的拥挤占主导地位。我们研究的一个目标是了解信息在神经元感受野的汇聚是如何导致拥挤的。 我们已经确定纹外皮质区V4可能参与字母状视觉刺激的相互作用，从而导致拥挤现象。这项拟议的研究考察了关于拥挤的神经机制的五个主要问题。1)拥挤的空间不对称性是由被称为皮质放大因子的空间信息的神经重新标度来解释的吗？2)相对于感受野中心的组织在神经元水平上决定拥挤交互作用吗？3)刺激大小在感受野内拥挤中起主要作用还是主要因素间距？4)注意力是通过改变拥挤区域内的基本敏感度来改变拥挤还是需要在不改变基本敏感度的情况下读出信息？5)抑制环境的影响在调节经典感受野内的拥挤交互时是关键的吗？这些问题将使用神经生理学技术来研究受试者在进行视觉注视和视觉注意辨别任务时单个皮质神经元的活动。 与公共卫生相关：数百万人现在患有限制中心视力的低视力障碍；这些障碍在老龄化人口中增加。这项研究计划的目标是了解视觉拥挤的神经机制，这种机制限制了阅读和驾驶等正常日常活动中外围视觉的使用。对基本神经机制的了解可以导致改进的临床方法，建议替代的康复方法，并提供更好的，更准确的视觉健康评估。

DESCRIPTION (provided by applicant): Our goal is to understand the neural mechanisms of visual crowding. Crowding is a stimulus interaction phenomenon that results in a blurring degradation of visual perception. Without moving the eyes only a small area of the visual scene gives rise to a clear visual experience. This area is known as the functional visual field. Within it we can select and scrutinize items, recognize and define their features and interrelated parts. Outside of it we have difficultly forming distinct, vivid impressions of the objects surrounding us. Our hypothesis is that the transition across the functional visual field boundary is governed by visual spatial crowding. Crowding plays a major role in limiting the remaining visual function of people with central visual field loss, e.g., macular degeneration, because it dramatically limits the use of the peripheral visual field for daily activities such as reading. Reading is especially slow for people with low vision from central field loss because of the dominance of crowding in the near periphery. A goal of our research is to understand how crowding results from the convergence of information in neuronal receptive fields. We have identified extrastriate cortical area V4 as an area likely to be involved in the interactions of letter-like visual stimuli that lead to crowding phenomena. The proposed research examines five principle questions about the neural mechanisms of crowding. 1) Are the spatial asymmetries of crowding explained by the neural rescaling of spatial information known as the cortical magnification factor? 2) Does organization with respect to the center of the receptive field play a critical role in determining crowding interactions at the neuronal level? 3) Does stimulus size play a major role in crowding within the receptive field or is the primary factor spacing? 4) Does attention alter crowding by changing the basic sensitivity within the crowded area or is it needed to readout information without altering the basic sensitivity? 5) Are the influences of the suppression surround critical in modulating the crowding interactions within the classic receptive field? These issues will be investigated using neurophysiological techniques to study the activity of single cortical neurons while subjects perform visual fixation and visual attentive discrimination tasks. PUBLIC HEALTH RELEVANCE: Millions of people now suffer from low vision disorders that limit central vision; these disorders increase within the aging population. The goal of this research program is to provide an understanding of the neural mechanisms of visual crowding that limit the use of the peripheral vision in normal daily activities such as reading and driving. Understanding of the basic neural mechanism can lead to enhanced clinical approaches, suggest alternate rehabilitative methods, and provide for better, more precise evaluations of visual health.