Contextual modulation of orientation specificity in V1

描述（由申请人提供）：本提案的目的是确定初级视觉皮层（V1）中上下文调制的潜在内在机制。虽然已知V1神经元取向选择的基本驱动来自外侧膝状核（LGN）的视网膜中继，但这种经典感受野（CRF）的调节是通过V1内的外侧远程连接产生的。这种环绕调制可以抑制或增强神经元对其CRF的反应。Sur实验室和其他人先前的工作表明，调制的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偏好取向域之间的转换可以是平滑的或断裂的（其中发现彼此相邻的不一致的取向域）。有迹象表明，这些裂缝位置的远程输入来自其他取向域的不均匀阵列，而光滑或等取向域则主要接收来自等取向域的横向连接。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中标记的细胞簇。通过将标记细胞的位置与取向偏好图相匹配，我们可以明确定义哪些区域提供调节输入。有了这些信息，我们可以谨慎地用最佳方向显示刺激这些区域，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.