Cortical Basis of Perceptual Grouping

描述(申请人提供)：拟议研究的长期目标是了解哺乳动物视觉系统进行场景分割的神经机制。在这个过程中，视觉系统被认为通过识别共同特征之间的关系将场景解析为其组成部分对象。分割的关键步骤是将定向特征分组成形成对象边界的轮廓。目前的证据表明，纹状皮质在轮廓整合过程中做出了基本的贡献，但其潜在的神经元表征还没有完全被理解。在这项拟议的研究中，我们计划监测行为猕猴纹状皮质中两个或两个以上位置的神经元组的活动，以测试轮廓整合与神经元关联的三个具体假说。我们将进行两组实验，在这些实验中，我们将建立轮廓显著、神经元活动和行为表现之间的关系。在第一个实验中，动物将被要求发出信号，在中央注视目标熄灭后，通过扫视眼球移动到其位置，以发出它们检测到嵌入背景中的外围轮廓的信号。在第二个实验中，在中央注视目标熄灭后，动物将被提示通过眼跳般的眼动来选择嵌入到背景中的两个相邻轮廓中的一个。在这两个实验中，通过改变组成轮廓的元素的方向来控制轮廓的显著程度，从而控制任务的难度。视觉刺激将由随机定向的Gabor面片阵列组成，其中面片的一个或两个子集将被对准以形成闭合轮廓。轮廓元素(S)或背景元素将被定位在细胞感受野上，以激活记录的神经元。这一范式将使我们能够保持激活细胞的局部刺激恒定，同时系统地操纵图形/背景关系、感知突显和轮廓的行为相关性。我们将分析产生的活动，以确定轮廓整合是否与射击率、时间相关性、反应潜伏期或这些变量的某种组合的特定变化相关。总之，这些实验将使我们能够研究纹状皮质轮廓整合的神经元相关性，并促进我们对场景分割过程的总体理解。

DESCRIPTION (provided by applicant): The long-term objective of the proposed research is to understand the neuronal mechanisms underlying scene segmentation by the mammalian visual system. In this process, the visual system is thought to parse a scene into its component objects by identifying relationships among common features. A critical step in segmentation is the grouping of oriented features into contours that form the boundaries of objects. Current evidence indicates that striate cortex makes a fundamental contribution to this process of contour integration, but the underlying neuronal representations are not fully understood. In the proposed research, we plan to monitor the activity of groups of neurons at two or more sites in striate cortex of behaving macaque monkeys, in order to test three specific hypotheses for the neuronal correlate of contour integration. We will conduct two sets of experiments in which we will establish the relations between contour salience, neuronal activity and behavioral performance. In the first experiment, the animals will be required to signal their detection of a peripheral contour embedded in a background by making a saccadic eye movement to its location after a central fixation target is extinguished. In the second experiment, the animals will be cued to select one of two adjacent contours embedded in a background by making a saccadic eye movement to the cued contour after a central fixation target is extinguished. In both experiments, the contour salience, and hence the task difficulty, will be controlled by varying the orientation of the elements comprising the contour. The visual stimuli will be composed of arrays of randomly oriented Gabor patches, in which one or two subsets of the patches will be aligned to form a closed contour. Elements of the contour(s) or background will be positioned over the cellular receptive fields to activate the recorded neurons. This paradigm will enable us to keep the local stimuli activating the cells constant while systematically manipulating the figure/ground relationships, the perceptual salience and the behavioral relevance of the contours. We will analyze the resulting activities to determine if contour integration is correlated with specific changes in firing rates, temporal correlations, response latencies or some combination of these variables. Together, these experiments will enable us to investigate the neuronal correlate of contour integration in striate cortex, and advance our understanding of scene segmentation processes in general.