Developing new paradigms for mouse forelimb sensorimotor circuit analysis

项目摘要 手部的感觉引导运动涉及到上行躯体感觉的整合和协调 信号和下行运动指令在神经系统的多个层次。大量的知识 关于主动触摸的神经生理学以及前肢躯体感觉和运动控制的相关方面 是从以人类和猴子为研究对象的研究中获得的。最近，使用小鼠的研究 能够对介导前肢的体感神经元进行广泛的分子和细胞表征， 相关功能。然而，小鼠前肢功能的神经生理学分析的局限性在于， 通常用于探测系统的振动触觉和其它机械类型的刺激具有固有的 它们在时空精度、速度、灵活性和复杂性方面的实际限制。这些限制反映了 小鼠前肢解剖结构的小尺寸和施加机械刺激的需要 通过直接的身体接触。相比之下，在视觉系统中，光的物理特性允许严格控制 传递复杂的刺激。我们在这个提案中的总体目标是开发新的研究范式， 基于“轻触”的小鼠前肢躯体感觉和运动功能：光遗传学激活 前肢/手的机械感觉传入，使用时空控制的光刺激。为此我们 将首先使用麻醉的小鼠来实现通过光纤光学传递光刺激的范例 或激光扫描光刺激（LSPS）。刺激技术将用于激活 在前肢中表达兴奋性视蛋白通道视紫红质-2（ChR 2）的小鼠的前肢/手 机械感受器传入，并与记录运动学、神经元的硬件和软件集成 大脑皮层和其他地方的峰值以及前肢肌肉活动。在第二个实验中，我们将 开发这种方法的多种变体，用于清醒行为的小鼠， 实验，如周边激活过程中的皮层沉默，触觉反应的高速映射， 动态刺激模式等等。总体结果将是增加和扩大现有的 用于研究小鼠前肢的基于躯体感觉的功能的实验范例， 补充了在小鼠中越来越多的遗传和病毒方法的可用性， 感觉引导运动中涉及的躯体感觉细胞类型及其回路 控制前肢。

PROJECT SUMMARY Sensory-guided movements of hands involve the integration and coordination of ascending somatosensory signals and descending motor commands at multiple levels of the nervous system. A great deal of knowledge about the neurophysiology of active touch and related aspects of forelimb somatosensation and motor control has been gained from studies using humans and monkeys as subjects. More recently, studies using mice are enabling extensive molecular and cellular characterizations of somatosensory neurons mediating forelimb- related functions. However, a limitation to neurophysiological analysis of mouse forelimb functions is that the vibrotactile and other mechanical types of stimuli that are commonly used to probe the system have inherent practical limitations in their spatiotemporal precision, speed, flexibility, and complexity. These limitations reflect the small dimensions of the mouse's forelimb anatomy and the need for mechanical stimuli to be applied through direct physical contact. In contrast, in the visual system, the physics of light permits tightly controlled delivery of complex stimuli. Our overall goal in this proposal is to develop new paradigms for investigating forelimb somatosensory and motor functions in the mouse based on “light touch”: optogenetic activation of mechanosensory afferents of the forelimbs/hands, using spatiotemporally controlled light stimuli. For this, we will first use anesthetized mice to implement paradigms for optical delivery of light stimuli through optical fibers or laser-scanning photostimulation (LSPS). The stimulation technology will be used to activate the forelimbs/hands of mice expressing the excitatory opsin channelrhodopsin-2 (ChR2) in forelimb mechanoreceptor afferents, and integrated with hardware and software for recording kinematics, neuronal spiking in cortex and elsewhere, and forelimb muscular activity. In a second series of experiments we will develop multiple variants of this approach for use with awake behaving mice, enabling diverse types of experiments such as cortical silencing during peripheral activation, high-speed mapping of tactile responses, dynamic stimulus patterns, and more. The overall outcome will be to augment and expand the available experimental paradigms for investigating somatosensory-based functions of the mouse's forelimb, complementing the growing availability in mice of genetic and viral methods for accessing and manipulating in a cell-type-specific manner the somatosensory cell types and their circuits involved in sensory-guided motor control of the forelimb.