Functional Organization of Somatosensory Cortex

描述（由申请人提供）：该项目的总体目标是了解神经元对感觉刺激的反应如何在大脑皮层中协调，无论是局部的还是跨连接的皮层区域。体感信息对于指导许多运动行为非常重要，这是通过从体感皮层到参与控制运动输出的大脑区域的投射来介导的。因此，增加对这些通路以及控制初级体感（SI）皮层和初级运动（Ml）皮层之间远程相互作用的机制的了解，应该有助于开发新的策略和技术，以康复遭受感觉障碍的脑损伤个体： 我们将使用啮齿动物 SI 桶状皮层作为动物模型来测试有关从 SI 到 MI 的皮质皮质投射的几个假设。对于特定目标 1，SI 桶状区域中逆行标记神经元的分布将在两种示踪剂离散沉积到 MI 的相邻焦点部位后进行表征。通过使用双追踪范例，我们将确定汇聚到 MI 皮层焦点位置的 SI 神经元的拓扑。对于特定目标 2，我们将同时记录 SI 桶状皮层中的多个神经元，以表征不同类型的神经元在感觉刺激过程中如何相互协调。因此，我们将表征以下之间放电的协调或相对时间：a)投射到MI的SI神经元对，b)不投射到M1的SI神经元对，以及c)异质的投射和非投射神经元对。对于特定目标 3，我们将同时记录 SI 和 MI 连接部分中的多个神经元，以测试 SI 中相邻投射神经元对相互协作以激活 MI 皮层中常见神经元目标的假设。为了解决这个问题，将使用条件互相关分析来量化 SI 中的同步活动对 MI 须表示的相应部分中神经元响应概率的影响。

DESCRIPTION (provided by applicant): The overall goal of this project is to understand how neuronal responses to sensory stimuli are coordinated in the cerebral cortex, both locally and across connnected cortical areas. Somatosensory information is important for guiding many motor behaviors, and this is mediated by projections from somatosensory cortex to brain regions involved in controlling motor output. Hence, increased knowledge of these pathways and the mechanisms that govern long-range interactions between the primary somatosensory (SI) cortex and the primary motor (Ml) cortex should facilitate the development of new strategies and techniques for rehabilitating brain-damaged individuals that suffer sensory impairment: We will use the rodent SI barrel cortex as an animal model to test several hypotheses concerning the corticocortical projections from SI to MI. For Specific Aim 1, the distribution of retrogradely-labled neurons in the barrel field of SI will be characterized following discrete deposits of two tracers into neighboring focal sites of MI. By using a dual tracing paradigm, we will determine the topography of SI neurons that converge on focal sites in MI cortex. For Specific Aim 2, we will simultaneously record multiple neurons in SI barrel cortex to characterize how different types of neurons are coordinated with each other during sensory stimulation. Thus, we will characterize the coordination or relative timing of discharges among: a) pairs of SI neurons that project to MI, b) pairs of SI neurons that do not project to Ml, and c) heterogeneous pairs of projection and non-projection neurons. For Specific Aim 3 we will simultaneously record multiple neurons in connected parts of SI and MI to test the hypothesis that neighboring pairs of projection neurons in SI cooperate with each other to activate common neuronal targets in MI cortex. To address this issue, conditional cross-correlation analysis will be used to quantify the impact of synchronized activity in SI on the probability of neuronal responsiveness in corresponding parts of the MI whisker representation.