Department of Kinesiology, University of Indianapolis - Indianapolis Center for Exercise Research [ICER], Indianapolis, IN 46227, USA.
Department of Kinesiology, Indiana University-Purdue University, Indianapolis, IN 46202, USA.
Neuroscience. 2022 Jul 15;495:15-24. doi: 10.1016/j.neuroscience.2022.05.026. Epub 2022 May 24.
A single pulse of high intensity electrical current delivered to the digits of the hand during voluntary contractions produces a period of decreased electromyographic (EMG) activity, known as a cutaneous silent period (CSP) (Caccia and Violini, 1973; Inghilleri et al., 1997; Uncini et al., 1991). Pairing transcranial magnetic stimulation (TMS) with digit stimulation results in motor evoked potentials (MEPs) with reduced amplitudes in a thenar muscle (Kofler, 2008). It is not known if similar behavior can be observed in more proximal upper-limb muscles. The current study investigated the CSP on several muscles throughout the upper-limb. Fourteen subjects performed isometric contractions with the following muscles: abductor pollicis brevis (APB), flexor carpi radialis (FCR), extensor carpi radialis (ECR), biceps brachii (BIC), triceps brachii (TRI), anterior deltoid (AD), and posterior deltoid (PD). During the isometric contractions, subjects experienced three different stimulation conditions: electrical stimulation (10x perceptual threshold) of digit II only (CSP), transcranial magnetic stimulation only (TMS), and a pairing of digit II stimulation and TMS (TMS+). The TMS evoked MEP was significantly greater than the TMS+ MEP for APB (p < 0.001), FCR (p = 0.006), and BIC (p < 0.049) muscles. The opposite relationship was seen within the PD (p < 0.047) muscle. An ANOVA test of normalized MEP values (TMS+/TMS) showed significant differences in APB vs TRI (p = 0.004) and PD (p = 0.003), and in FCR vs TRI (p = 0.046) and PD (p = 0.037) muscles. The results suggest that the CSP modulates descending drive differentially across upper-limb muscles.
在自愿收缩期间，施加于手部指尖的高强度单脉冲电流会产生一段肌电图（EMG）活动减少的时期，称为皮肤静息期（CSP）（Caccia 和 Violini，1973；Inghilleri 等人，1997；Uncini 等人，1991）。经颅磁刺激（TMS）与指尖刺激相结合会导致鱼际肌的运动诱发电位（MEP）幅度减小（Kofler，2008）。目前尚不清楚在更靠近上肢的肌肉中是否可以观察到类似的行为。本研究调查了上肢多个肌肉的 CSP。14 名受试者使用以下肌肉进行等长收缩：拇指外展短肌（APB）、桡侧腕屈肌（FCR）、桡侧腕伸肌（ECR）、肱二头肌（BIC）、肱三头肌（TRI）、三角肌前束（AD）和三角肌后束（PD）。在等长收缩期间，受试者经历了三种不同的刺激条件：仅刺激 II 指的电刺激（CSP）、仅 TMS 刺激和 II 指刺激与 TMS 的配对（TMS+）。TMS 诱发的 MEP 明显大于 APB（p<0.001）、FCR（p=0.006）和 BIC（p<0.049）的 TMS+MEP。在 PD 肌肉中则出现相反的关系（p<0.047）。TMS+/TMS 归一化 MEP 值的 ANOVA 检验显示，APB 与 TRI（p=0.004）和 PD（p=0.003）以及 FCR 与 TRI（p=0.046）和 PD（p=0.037）肌肉之间存在显著差异。结果表明，CSP 在上肢肌肉之间不同程度地调节下行驱动。
