Contextual modulation of orientation specificity in V1

描述（由申请人提供）：该提案的目的是确定初级视觉皮层（V1）中上下文调节的潜在内在机制。尽管已知 V1 神经元方向选择性的基本驱动源自外侧膝状核 (LGN) 的视网膜中继，但这种经典感受野 (CRF) 的调制是通过 V1 内的外侧长程连接产生的。这种环绕调制可以抑制或增强神经元对其 CRF 的响应。 Sur 实验室和其他实验室之前的工作表明，调制方向取决于环绕的方向和 CRF 的对比度。此外，取向偏好图的排列使得优选取向域之间的过渡可以是平滑的或断裂的（其中发现不一致的取向域彼此相邻）。有迹象表明，这些断裂部位的远程输入来自其他方向域的非均匀阵列，而已知平滑或等方向域主要接收来自类似等方向域的横向连接。拟议的实验将使用光学成像来识别荧光示踪剂注射的断裂部位，并使用双光子显微镜来识别 V1 中标记细胞的最终簇。通过将标记细胞的位点与方向偏好图进行匹配，我们可以具体定义哪些区域提供调节输入。有了这些信息，我们可以通过最佳方向显示谨慎地刺激这些区域，并系统地测量对 CRF 的影响。

DESCRIPTION (provided by applicant): The aim of this proposal is to identify the underlying intrinsic mechanisms of contextual modulation in primary visual cortex (V1). Though the basic drive of orientation selectivity of V1 neurons is known to derive from retinal relays of the lateral geniculate nucleus (LGN), modulation of this classical receptive field (CRF) is generated through lateral long-range connections within V1. This surround modulation can either suppress or enhance the response of a neuron to its CRF. Previous work from the Sur lab and others has shown that the direction of the modulation depends on the orientation of the surround and the contrast of the CRF. Furthermore, orientation preference maps are arranged so that transitions between preferred orientation domains can be smooth or fractured (where incongruent orientation domains are found adjacent to each other). There are indications that long-range inputs to these fracture sites come from an in-homogenous array of other orientation domains, whereas smooth, or iso-orientation domains are known to receive lateral connections primarily from like iso-orientation domains. The proposed experiments will use optical imaging to identify fracture sites for fluorescent tracer injections, and two-photon microscopy will be used to identify the resulting clusters of labeled cells in V1. By matching the sites of labeled cells with the orientation preference map we can define specifically which regions provide modulatory input. With this information we can discreetly stimulate these regions with optimal orientation displays and systematically measure the effects on the CRF.