CONTRAST, CONTEXT AND STIMULUS GROUPING IN STRIATE CELLS

完形知觉理论认为视觉系统将特征 在相似性、接近性、平滑性和封闭性的基础上， 最近的心理生理学和神经生理学研究发现， 空间易化和抑制，这似乎符合 知觉分组规则感知分组可以通过以下方式来实现： 视觉皮层的长距离横向连接最近，我们发现， 单细胞对中心靶点的反应受到共线 侧面的物体这种调制依赖于细胞的对比度 中心目标的门槛。我们假设 区域17中的相互作用被安排成两个对抗机制： 1)促进作用是空间组织的沿着最佳方向， 2）抑制是非选择性的， 方向或空间频率，并扩散分布在周围的 细胞的反应。这两种机制之间的平衡，决定了 通过细胞的对比度阈值来控制细胞的放电。基于 根据这一假设，我们将研究以下四个问题， 生理记录的单细胞从视觉皮层的 麻醉和麻痹制剂。 目的l将回答的问题是否上下文相关的调制 细胞反应的大小取决于细胞的对比度 阈值，而不是刺激的物理对比。我们想 了解对比度阈值依赖性促进作用的普遍程度， 镇压是。 目标2将剖析调制的空间组织 交互. 特别是，我们将阐明一个组织 原则沿着研究中的细胞的最佳方向。 目标3将研究目标和侧翼之间距离的影响， 大小和它们的空间频率对调节相互作用的影响。这 aim的重点是目标的相似性和接近性问题， 侧翼 目标4将扩展我们对知觉分组的神经基础的探索 领先一步，使用由曲线中的许多元素组成的复合刺激。我们 将回答是否单细胞反应不同时，最佳 定位的测试刺激是平滑弯曲路径或圆的一部分 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.