Graham Kylee R, Hayes Kara D, Meehan Sean K
Department of Kinesiology and Health Sciences, University of Waterloo.
Department of Kinesiology and Health Sciences, University of Waterloo;
J Vis Exp. 2023 Apr 21(194). doi: 10.3791/65212.
Skilled motor ability depends on efficiently integrating sensory afference into the appropriate motor commands. Afferent inhibition provides a valuable tool to probe the procedural and declarative influence over sensorimotor integration during skilled motor actions. This manuscript describes the methodology and contributions of short-latency afferent inhibition (SAI) for understanding sensorimotor integration. SAI quantifies the effect of a convergent afferent volley on the corticospinal motor output evoked by transcranial magnetic stimulation (TMS). The afferent volley is triggered by the electrical stimulation of a peripheral nerve. The TMS stimulus is delivered to a location over the primary motor cortex that elicits a reliable motor-evoked response in a muscle served by that afferent nerve. The extent of inhibition in the motor-evoked response reflects the magnitude of the afferent volley converging on the motor cortex and involves central GABAergic and cholinergic contributions. The cholinergic involvement in SAI makes SAI a possible marker of declarative-procedural interactions in sensorimotor performance and learning. More recently, studies have begun manipulating the TMS current direction in SAI to tease apart the functional significance of distinct sensorimotor circuits in the primary motor cortex for skilled motor actions. The ability to control additional pulse parameters (e.g., the pulse width) with state-of-the-art controllable pulse parameter TMS (cTMS) has enhanced the selectivity of the sensorimotor circuits probed by the TMS stimulus and provided an opportunity to create more refined models of sensorimotor control and learning. Therefore, the current manuscript focuses on SAI assessment using cTMS. However, the principles outlined here also apply to SAI assessed using conventional fixed pulse width TMS stimulators and other forms of afferent inhibition, such as long-latency afferent inhibition (LAI).
熟练的运动能力取决于将感觉传入有效地整合到适当的运动指令中。传入抑制为探究熟练运动行为期间对感觉运动整合的程序性和陈述性影响提供了一个有价值的工具。本手稿描述了短潜伏期传入抑制（SAI）在理解感觉运动整合方面的方法和贡献。SAI量化了汇聚的传入冲动对经颅磁刺激（TMS）诱发的皮质脊髓运动输出的影响。传入冲动由外周神经的电刺激触发。TMS刺激施加到初级运动皮层上方的一个位置，该位置在由该传入神经支配的肌肉中引发可靠的运动诱发电反应。运动诱发电反应中的抑制程度反映了汇聚到运动皮层的传入冲动的大小，并涉及中枢γ-氨基丁酸能和胆碱能的作用。胆碱能参与SAI使SAI成为感觉运动表现和学习中陈述性-程序性相互作用的一个可能标志。最近，研究开始在SAI中操纵TMS电流方向，以区分初级运动皮层中不同感觉运动回路对熟练运动行为的功能意义。利用最先进的可控脉冲参数TMS（cTMS）控制额外脉冲参数（如脉冲宽度）的能力提高了TMS刺激所探测的感觉运动回路的选择性，并为创建更精细的感觉运动控制和学习模型提供了机会。因此，本手稿重点关注使用cTMS进行的SAI评估。然而，这里概述的原理也适用于使用传统固定脉冲宽度TMS刺激器评估的SAI以及其他形式的传入抑制，如长潜伏期传入抑制（LAI）。
