MECHANISMS OF VISUAL CONTEXT EFFECTS IN VISUAL CORTEX

在经典感受野（可以引起反应的视野区域）以外的位置的视觉刺激可以对视觉皮层中神经元反应的选择性和幅度产生深远的影响，即使这些刺激本身没有引起反应。一般认为，内在的解剖学联系是这些调节作用的基础。理解皮层神经元的反应是如何被这种调节效应所塑造的，对于理解皮层组织在决定皮层功能中的作用，以及大脑的视觉区域如何处理复杂的现实世界场景是很重要的。在这项研究中，我们将阐明视觉刺激的空间分布是如何塑造视觉皮层中的神经元反应的，我们将阐明连接皮层上不同点（因此是不同的空间位置）的解剖学基础。因此，这将允许直接测试局部皮层连接是否确实是这些调节环绕效应的基础。1)在成年猴子和雪貂的电生理和神经解剖学实验中，我们将测试来自经典感受野以外的反应抑制或增强的空间范围和地形是否可以用初级视觉皮层（V1）和V2内局部水平或皮质反馈连接的分布来解释。2)在成年猴子和雪貂的电生理研究中，我们将探索V1和V2经典感受野之外的反应调节的刺激特异性。我们将重点关注V1作为通往其他皮质视觉区域的门户，但也将研究V2以阐明这些调节效应对所有皮质视觉区域的一般性质和功能。3)在雪貂的发育研究中，我们将在大范围的出生后年龄范围内系统地比较调节环绕效应的发展与经典感受野反应的发展，以及V1的内在和外在连接的改进。这将使我们能够将调制效应的发展细化与经典感受野特性进行比较，并进一步测试内在连接是否可以作为环绕调制的基础。将不同解剖回路的选择性和空间范围的细节与生理学研究的相似细节进行比较，将为理解哪些解剖回路是特定功能的基础，以及神经元功能和连通性如何影响视觉表现提供关键信息。这是理解大脑皮层在视觉和高级认知功能方面是如何工作的一个基本问题。

Visual stimuli at locations beyond the classical receptive field (the area of the visual field from which responses can be evoked) can have profound effects on the selectivity and magnitude of neuronal responses in the visual cortex, even when these stimuli do not themselves evoke responses. It is generally assumed that intrinsic anatomical connections underlie these modulatory effects. Understanding how cortical neuron responses are shaped by such modulatory effects is important for understanding the role of cortical organization in determining cortical function, and in how the visual areas of the brain process complex real- world scenes. In this study we will clarify how neuronal responses in visual cortex are shaped by the spatial distribution of visual stimuli, and we will elucidate the anatomical substrates that link different points on the cortex (and therefore different spatial locations). This will therefore permit a direct test of whether local cortical connections do in fact underlie these modulatory surround effects. 1) In electrophysiological and neuroanatomical experiments in adult monkeys and ferrets, we will test whether the spatial extent and topography of response suppression or enhancement from beyond the classical receptive field can be accounted for by the distribution of local horizontal or cortical feedback connections within primary visual cortex (V1) and V2. 2) In electrophysiological studies in adult monkeys and ferrets, we will explore the stimulus specificity of response modulation from beyond the classical receptive field in V1 and V2. We will focus on V1 as the gateway to other cortical visual areas, but will also examine V2 to illuminate how general the properties and function of these modulatory effects are to all cortical visual areas. 3) In developmental studies in ferrets, we will systematically compare, across a large range of postnatal ages, the development of the modulatory surround effects to that of the responses in the classical receptive field, and to the refinement of intrinsic and extrinsic connections in V1. This will allow us to compare the developmental refinement of the modulatory effects to classical receptive field properties, and to further test whether intrinsic connections can underlie surround modulation. Comparison of details of the selectivity and spatial extent of different anatomical circuits with similar details from physiological investigations will provide information critical to an understanding of which anatomical circuits underlie particular functions, and in how neuronal function and connectivity underlie visual performance. This is a fundamental question in understanding how the cerebral cortex works, both in vision and in higher cognitive function.