Mechanisms of Visual Motion Perception

描述(申请人提供)：视觉处理面临两个相互冲突的需求：整合和分割。固有的噪声视觉信号需要整合，而分割则需要从视觉输入的时空变化中提取重要信息。理解这两种机制之间的相互作用将揭示视觉处理的基本原理，并有助于深入了解分割过程的功能角色。在运动感知方面，PI最近的工作表明，运动信号的空间整合并不是固定的，而是关键取决于基本的视觉因素，如对比度，随着刺激能见度的增加，空间整合让位于空间抑制。该方案的主要目标是研究运动信号的自适应整合/分离所涉及的神经机制，并阐明它们在从运动背景中分割对象方面的作用。空间抑制的关键特征是对大的、高对比度的刺激的运动知觉受损。在目标1中，我们将确定这种抑制机制是否以及如何影响视觉和动眼加工。回答这个问题将限制空间抑制的可能的神经关联，并与目标2一起，为将空间抑制与MT区的环绕抑制联系起来的假设提供一个检验。证实这种联系将允许将空间抑制和运动分离(目标2和3)之间的联系归因于MT环绕抑制的参与。在目标2中，我们将通过损害MT和TMS早期视觉区域的加工来寻找神经与空间抑制的相关性的直接证据。我们预计，对空间抑制至关重要的神经机制的破坏，将允许通常被抑制的运动信号到达知觉。同时，我们还将确定削弱空间抑制的同一刺激是否也扰乱了运动分离。在目标3中，我们测试了这样的假设，即空间抑制通过抑制背景运动信号直接实现运动对象的快速分离。这里，空间抑制在运动分离中的作用被概念化为一个粗略但快速的基于区域的分割过程。这一假设预测，空间抑制的变化(因此，背景运动的可见性)应该预测运动分离的相应变化，反之亦然。利用不同的实验方法，我们将利用刺激操作、个体差异和知觉学习来测试这一预测，以产生空间抑制或运动分离的变化。其中一个重点将放在老年人身上，众所周知，他们表现出弱的空间抑制。我们将确定这种异常是否预示着运动分离缺陷，以及与年龄相关的空间抑制缺陷是否可以通过对运动分离的知觉学习而逆转。

DESCRIPTION (provided by applicant): Visual processing faces two conflicting demands: integration and segmentation. Integration is required by inherently noisy visual signals, while segmentation is needed to extract vital information from spatiotemporal variations in visual input. An understanding of the interplay between these two mechanisms will reveal fundamentals of visual processing and also enable insights into functional roles of segmentation processes. In motion perception, the PI's recent work demonstrated that spatial integration of motion signals is not fixed, but critically depends on basic visual factors such as contrast, with spatial integration giving way to spatial suppression as stimulus visibility increases. The overarching goal of this proposal is to investigate the neural mechanisms involved in this adaptive integration/segregation of motion signals, and to elucidate their role in the segmentation of objects from moving backgrounds. The key property of spatial suppression is impaired motion perception of large, high-contrast stimuli. In Aim 1, we will determine if and how this suppressive mechanism affects visual and oculomotor processing. Answering this question will constrain possible neural correlates of spatial suppression and, along with Aim 2, provide a test for the hypothesis linking spatial suppression to surround suppression in area MT. Substantiating this link will allow the attribution of links between spatial suppression and motion segregation (Aims 2 & 3) to the involvement of MT surround suppression. In Aim 2, we will seek direct evidence about neural correlates of spatial suppression by impairing processing in MT and early visual areas with TMS. We expect that a disruption of neural mechanisms critically involved in spatial suppression will allow normally suppressed motion signals to reach perception. Concurrently, we will also determine whether the same stimulation that impairs spatial suppression also disrupts motion segregation. In Aim 3, we test the hypothesis that spatial suppression directly enables rapid segregation of moving objects by suppressing background motion signals. Here, the role of spatial suppression in motion segregation is conceptualized as a coarse, but rapid, region-based segmentation process. This hypothesis predicts that variations in spatial suppression (and, thus, in the visibility of background motion) should predict corresponding changes in motion segregation and vice versa. Exploiting different experimental approaches, we will test this prediction by utilizing stimulus manipulations, individual differences and perceptual learning to produce variations in either spatial suppression or motion segregation. One focus will be on older adults, who are known to exhibit weak spatial suppression. We will determine whether this abnormality predicts motion segregation deficits and whether age-related deficits in spatial suppression can be reversed by the perceptual learning of motion segregation.