Department of Exercise Sciences, The University of Auckland, Auckland, New Zealand.
Department of Medicine, The University of Auckland, Auckland, New Zealand.
J Neurophysiol. 2024 Oct 1;132(4):1223-1230. doi: 10.1152/jn.00262.2024. Epub 2024 Sep 18.
The ability to perform intricate movements is crucial for human motor function. The neural mechanisms underlying precision and power grips are incompletely understood. Corticospinal output from M1 is thought to be modulated by GABA-ergic intracortical networks within M1. The objective of our study was to investigate the contribution of M1 intracortical inhibition to fine motor control using adaptive threshold hunting (ATH) with paired-pulse TMS during pinch and grasp. We hypothesized that short-interval intracortical inhibition (SICI) could be assessed during voluntary activation and that corticomotor excitability and SICI modulation would be greater during pinch than grasp, reflecting corticospinal control. Seventeen healthy participants performed gradual pinch and grasp tasks. Using ATH, paired-pulse TMS was applied in the anterior-posterior current direction to measure MEP latencies, corticomotor excitability, and SICI. MEP latencies indicated that the procedure preferentially targeted late I-waves. In terms of corticomotor excitability, there was no difference in the TMS intensity required to reach the MEP target during pinch and grasp. Greater inhibition was found during pinch than during grasp. ATH with paired-pulse TMS permits investigation of intracortical inhibitory networks and their modulation during the performance of dexterous motor tasks revealing a greater modulation of GABA-ergic inhibition contributing to SICI during pinch compared with grasp. Primary motor cortex intracortical inhibition was investigated during dexterous manual task performance using adaptive threshold hunting. Motor cortex intracortical inhibition was uniquely modulated during pinching versus grasping tasks.
执行精细运动的能力对人类运动功能至关重要。精确和有力抓握的神经机制尚未完全了解。人们认为，M1 的皮质脊髓输出受 M1 内 GABA 能皮质内网络的调制。我们研究的目的是使用自适应阈值狩猎（ATH）结合双脉冲 TMS 在捏合和抓握期间，研究 M1 皮质内抑制对精细运动控制的贡献。我们假设可以在自愿激活期间评估短程皮质内抑制（SICI），并且在捏合时皮质运动兴奋性和 SICI 调节会比抓握更大，反映皮质脊髓控制。17 名健康参与者进行了逐渐的捏合和抓握任务。使用 ATH，以前后电流方向施加双脉冲 TMS，以测量 MEP 潜伏期、皮质运动兴奋性和 SICI。MEP 潜伏期表明该程序优先靶向晚期 I 波。就皮质运动兴奋性而言，在捏合和抓握期间，达到 MEP 目标所需的 TMS 强度没有差异。在捏合时发现的抑制作用大于在抓握时。使用 ATH 结合双脉冲 TMS 可以研究皮质内抑制网络及其在灵巧运动任务中的调节，揭示了在捏合时 GABA 能抑制的更大调节有助于 SICI，与抓握相比。使用自适应阈值狩猎研究了灵巧手动任务执行期间的初级运动皮层皮质内抑制。运动皮层皮质内抑制在捏合与抓握任务之间独特地调节。
