Mechanisms of electrical stimulation of a canonical motor microcircuit

脊髓的神经回路有一个独特的，重复的结构，形成了一个特别有前途的， 通过电刺激控制目标。此外，这种结构允许基本电路用于 在脊髓损伤（SCI）的水平以下保持运动的产生。电刺激 因此，针对这些剩余感觉运动回路的技术成为非常有前途的疗法。 这些方法通常利用脊柱解剖学的另一个基本方面，即所有感觉轴突 通过一个非常容易到达的位置进入脊髓，它的背表面。因此，背侧电刺激（DES）通过 表面电极提供感觉轴突的有效激活而不需要穿透电极。 这些感觉轴突的脊髓连接介导对脊髓运动回路的有效影响。在这 建议，我们研究DES的神经机制，以明确其控制运动输出的潜力 并为改善其治疗实施创造合理的基础。DES的基本目标是 重建从大脑到脊髓的下行输入的关键功能，这些功能当然会受损或丢失 在SCI。因此，一个基本的问题是，感觉轴突的DES能在多大程度上复制 脊髓神经元的下行输入。为了解决这个问题，我们集中在典型的电机微电路 (CMM)，它包括一组拮抗剂运动池和处理其感觉的局部回路。 肌肉长度和速度的反馈。传递这一信息的Ia组轴突很大， 对DES比任何其他类型的感觉输入都更敏感。我们采用多种技术，包括 感觉轴突的轴突内记录、中间神经元的细胞外记录和 运动神经元我们的目的是绘制兴奋性和抑制性突触输入的分布， CMM通过DES，确定脊髓神经元的内在电特性在处理这些过程中的作用， 输入，评估DES对感觉轴突的激活是否干扰了它们的正常功能， 当由DES或正常感觉输入驱动时，作为CMM稳定性和焦点基础的机制。 拟议的研究将为脊髓DES提供基本的基础，并可能 确定改善其治疗效果的新机会。

The neural circuitry of the spinal cord has a unique, repetitive structure that forms an especially promising target for control via electrical stimulation. Furthermore, this structure allows the essential circuits for generation of movements to be preserved below the level of a spinal cord injury (SCI). Electrical stimulation techniques targeted at these remaining sensorimotor circuits are thus becoming highly promising therapies. These approaches usually take advantage of another basic aspect of spinal anatomy, that all sensory axons enter the cord via a highly accessible location, its dorsal surface. Thus dorsal electrical stimulation (DES) via surface electrodes provides effective activation of sensory axons without the need for penetrating electrodes. The spinal connections of these sensory axons mediate potent effects on spinal motor circuits. In this proposal, we examine the neural mechanisms of DES to clearly define its potential for controlling motor output and to create a rational basis for improving its therapeutic implementation. The basic goal of DES is to recreate key functions of the descending inputs from the brain to the cord, which are of course damaged or lost in SCI. Thus a fundamental question is, how well can DES of sensory axons replicate the effects of descending inputs on spinal neurons. To address this question, we focus on the canonical motor microcircuit (CMM), which comprises a single set of antagonist motor pools and the local circuits that process their sensory feedback about muscle length and velocity. The group Ia axons conveying this information are large and likely to be more sensitive to DES than any other type of sensory input. We apply multiple techniques, including intra-axonal recording in sensory axons, extracellular recording of interneurons and voltage clamp in motoneurons. Our Aims are to map the distribution of excitatory and inhibitory synaptic input generated in the CMM by DES, identify the roles of the intrinsic electrical properties of spinal neurons in processing these inputs, assess whether DES activation of sensory axons interferes with their normal function and probe the mechanism that underlie the stability and focus of the CMM when driven by DES or normal sensory inputs. The proposed studies will provide a fundamental underpinning for DES of the spinal cord and are likely to identify new opportunities for improvement its therapeutic effectiveness.