CONTRAST, CONTEXT AND STIMULUS GROUPING IN STRIATE CELLS

完形知觉理论认为，视觉系统将特征组合在一起 在相似、接近、平滑和闭合的基础上聚集在一起。 最近的心理物理和神经生理学研究发现了证据 空间促进和抑制似乎符合 感性分组规则。感知分组可以通过以下方式来实现 视皮层中的远距离侧向连接。最近，我们发现， 单细胞对中心靶点的反应受共线调节 侧翼的物体。这种调制取决于细胞的对比度 中央目标的阈值。我们假设侧向的 区域17中的相互作用被安排成两种对抗机制： 1)促进是沿着以下最佳方向在空间上组织的 共线方式的单元格；2)抑制对于 方向性或空间频率，并广泛分布在 单元格的响应字段。这两种机制之间的平衡，决定了 通过细胞的对比度阈值，控制细胞的激发。基于 在这一假设下，我们将通过以下四个问题进行研究 大鼠视皮层单个细胞的生理记录 麻醉和麻痹的制剂。 目的L将回答这样一个问题：语境依赖的调制是否 细胞的反应取决于相对于细胞对比度的对比度 阈值，而不是刺激的物理对比度。我们要 要了解对比度阈值依赖的促进和 压制才是。 目标2将剖析调制的空间组织 互动。特别是，我们将阐明一个组织 沿着被研究细胞的最优取向的原则。 目标3将研究目标与侧翼、侧翼之间的距离的影响 大小以及它们的空间频率对调制相互作用的影响。这 AIM的重点是目标和目标的相似性和贴近性问题 侧翼。 目标4将扩展我们对知觉分组的神经基础的研究 领先一步，使用由曲线上的许多元素组成的复合刺激。我们 将回答单个细胞在最佳情况下是否有不同的反应 定位测试刺激是平滑曲线路径或圆的一部分 由许多与测试贴片相同的图案组成。

Gestalt perceptual theory says that the visual system groups features together on the basis of similarity, proximity, smoothness and closure. Recent psychophysical and neurophysiolgical studies have found evidence of spatial facilitation and suppression that appears to conform to the perceptual grouping rules. The perceptual grouping may be implemented by long-range lateral connections in visual cortex. Recently, we found that single-cell responses to a central target were modulated by collinear flanking objects. This modulation was dependent on the cell's contrast threshold for the central target. We hypothesized that the lateral interactions in area 17 are arranged into two antagonistic mechanisms: 1) Facilitation is spatially organized along the optimal orientation of the cell in a collinear manner; 2) Suppression is non-selective for orientation or spatial frequency, and is distributed diffusely around the cell's response field. The balance between these two mechanisms, dictated by the cell's contrast threshold, controls the cells firing. Based on this hypothesis, we will study the following four questions by physiological recording of single cells from the visual cortex of anesthetized and paralyzed preparations. Aim l will answer the question whether the context-dependent modulation of cellular responses depends on contrast relative to the cell's contrast threshold, rather than on the physical contrast of the stimulus. We want to know how general the contrast threshold-dependent facilitation and suppression is. Aim 2 will dissect the spatial organization of the modulatory interactions. In particular, we will elucidate an organizational principle along the optimal orientation of the cell under study. Aim 3 will study effects of distance between target and flanks, flanks size, and their spatial frequency on the modulatory interactions. This aim is focused on an issue of similarity and closeness of target and flanks. Aim 4 will extend our search of the neural basis of perceptual grouping one step ahead, using compound stimuli made of many elements in curve. We will answer whether single cells respond differently when the optimally positioned test stimulus is a part of a smoothly curved path or circle composed of many of the same patterns as the test patch.