Optogenetic modulation of inhibition in cat visual cortex

项目总结 初级视皮层的图像表征在很大程度上依赖于激活的时空模式 分布式视觉皮质网络。这种激活依赖于视觉场景中对比度的分布，但是 也部分用于连接皮质的颗粒上层2-3中水平连接的脚手架 方向相似的柱。对于单个视觉皮质细胞，其空间上定义良好的感受野(RF) 不足以解释它们对视觉场景的视觉反应。事实上，视觉刺激下降的背景 射频之外是细胞反应的关键组成部分。这样的影响被称为语境效应， 它们取决于RF内部和外部的视觉刺激之间的相对属性，并且可以 促进的、抑制的或者它们可以调节神经元的增益(输入-输出函数的斜率)。一个 理解语境刺激的潜在机制的根本障碍是 在皮质柱的中尺度上操纵抑制。在这里，在目标1中，我们建议在 猫的光遗传方法，允许以极高的时间敏感度操纵抑制。我们将使用 基于DLX同源框基因增强子mDlx选择性表达的新策略 所有脊椎动物的皮质GABA能中间神经元。我们将(从宾夕法尼亚大学矢量核心)采购和 注射含有去极化(ChR2)和超极化(ARCHT)Opsins的AAV载体 MDLx.我们将通过电生理学和免疫组织化学验证选择性表达，并将校准 蓝绿光对视觉刺激反应的影响及规则和快速电流注入 刺激性神经元在活体细胞内记录。目标1的工作将在约翰·沃尔夫博士的帮助下完成 兽医学院是基因治疗病毒方法方面的专家。在目标2中，我们将获得 GABA能抑制在环绕声抑制和增益调制中作用的初步数据 语境刺激。除了为未来的R01应用提供强大的初步数据外，该项目还将实施 这种方法将允许在高度视觉的动物中解决超过50年的问题。

PROJECT SUMMARY Image representation in primary visual cortex depends critically on the spatiotemporal pattern of activation of distributed visual cortical networks. Such activation relies on distribution of contrasts in the visual scene but also in part in the scaffolding of horizontal connections in supragranular layers 2-3 that connect cortical columns of similar orientation. For individual visual cortical cells their spatially well defined receptive field (RF) is not sufficient to explain their visual responses to visual scenes. Indeed, the context of visual stimuli falling outside of the RF is a critical component of the cell response. Such effects have been called contextual effects, they depend on the relative properties between the visual stimulus inside and outside of the RF and can be facilitatory, inhibitory or they can modulate the gain (the slope of the input-output function) of the neuron. A fundamental impediment to understanding the underlying mechanisms of contextual stimuli is the ability of manipulating inhibition at the mesoscale of the cortical column. Here, in Aim 1 we propose to implement in the cat optogenetic approaches that allow to manipulate inhibition with great temporal sensitivity. We will use a strategy developed recently based on the selective expression of the DLX homeobox gene enhancer mDlx in cortical GABAergic interneurons of all vertebrate species. We will procure (from the Penn Vector Core) and inject AAV vectors containing depolarizing (ChR2) and hyperpolarizing (ArchT) opsins under the control of mDLx. We will verify selective expression with electrophysiology and inmunohistochemistry and will calibrate the effect of blue and green light on the responses to visual stimuli and current injection of regular and fast spiking neurons recorded intracellularly in vivo. Work in Aim 1 will be done with the help of Dr. John Wolfe from the Veterinary School which is an expert in viral approaches for gene therapy. In Aim 2 we will obtain preliminary data on the role of GABAergic inhibition in surround suppression and gain modulation caused by contextual stimuli. In addition to strong preliminary data for a future R01 application this project will implement an approach that will allow addressing over 50 year old questions in a highly visual animal.