Neural Mechanisms of Visual Crowding

描述（由申请人提供）：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的现象，导致视觉感知的模糊退化。在不移动眼睛的情况下，只有视觉场景的一小部分区域产生清晰的视觉体验。这个区域被称为功能性视野。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清晰、生动的印象。我们的假设是，跨越功能视野边界的过渡是由视觉空间拥挤决定的。拥挤在限制具有中央视野丧失的人的剩余视觉功能方面起主要作用，例如，黄斑变性，因为它极大地限制了周边视野用于日常活动如阅读的使用。由于近边缘区域的拥挤占主导地位，因此对于因中央视野丧失而视力低下的人来说，阅读尤其缓慢。我们研究的一个目标是了解神经元感受野中信息的会聚是如何导致拥挤的。 我们已经确定了纹外皮质区V4作为一个地区可能参与的相互作用的字母一样的视觉刺激，导致拥挤的现象。拟议的研究探讨了五个原则问题的神经机制的拥挤。1)拥挤的空间不对称性是否可以用被称为皮层放大因子的空间信息的神经重新调整来解释？2)组织相对于中心的感受野发挥关键作用，在确定拥挤的相互作用在神经元水平？3)刺激大小在感受野内的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程度，还是需要在不改变基本敏感度的情况下读出信息？5)在经典感受野中，抑制环境的影响对调节拥挤相互作用是否至关重要？这些问题将使用神经生理学技术进行调查，研究单个皮层神经元的活动，而受试者执行视觉固定和视觉注意力的歧视任务。 公共卫生相关性：现在有数百万人患有限制中心视力的低视力障碍;这些疾病在老龄化人口中增加。这项研究计划的目标是提供一个视觉拥挤的神经机制，限制使用的周边视觉在正常的日常活动，如阅读和驾驶的理解。了解基本的神经机制可以导致增强的临床方法，建议替代康复方法，并提供更好，更精确的视觉健康评估。

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.