Bolzoni Francesco, Bruttini Carlo, Esposti Roberto, Castellani Carlotta, Cavallari Paolo
Section of Human Physiology of the DePT, Università degli Studi di Milano, Via Mangiagalli 32, 20133 Milano, Italy.
Behav Brain Res. 2015 Sep 15;291:407-413. doi: 10.1016/j.bbr.2015.05.044. Epub 2015 Jun 5.
Recent works provide evidences that anticipatory postural adjustments (APAs) are programmed with the prime mover recruitment as a shared posturo-focal command. However the ability of the CNS to adjust APAs to changes in the postural context implies that the postural and voluntary components should take different pathways before reaching the representation of single muscles in the primary motor cortex. Here we test if such bifurcation takes place at the level of the supplementary motor area (SMA). TDCS was applied over the SMA in 14 subjects, who produced a brisk index-finger flexion. This activity is preceded by inhibitory APAs, carved in the tonic activity of Biceps Brachii and Anterior Deltoid, and by an excitatory APA in Triceps Brachii. Subjects performed a series of 30 flexions before, during and after 20 min of tDCS in CATHODAL, ANODAL or SHAM configuration. The inhibitory APA in Biceps and the excitatory APA in Triceps were both greater in ANODAL than in SHAM and CATHODAL configurations, while no difference was found among the latter two (ANODAL vs. SHAM: biceps +26.5%, triceps +66%; ANODAL vs. CATHODAL: biceps +20.5%, triceps: +63.4%; for both muscles, ANOVA p<0.02, Tukey p<0.05). Instead, the APA in anterior deltoid was unchanged in all configurations. No changes were observed in prime mover recruitment and index-finger kinematics. Results show that the SMA is involved in modulating APAs amplitude. Moreover, the differential effect of tDCS observed on postural and voluntary commands suggests that these two components of the motor program are already separated before entering SMA.
近期研究表明，预期姿势调整（APAs）是作为一种共享的姿势焦点指令与原动肌募集一起进行编程的。然而，中枢神经系统（CNS）将APAs调整以适应姿势背景变化的能力意味着，姿势和自主成分在到达初级运动皮层中单个肌肉的表征之前应该走不同的路径。在此，我们测试这种分支是否发生在辅助运动区（SMA）水平。对14名受试者的SMA施加经颅直流电刺激（TDCS），这些受试者进行快速的食指屈曲动作。此动作之前有抑制性APAs，表现为肱二头肌和三角肌前部的紧张活动减弱，以及肱三头肌的兴奋性APAs。受试者在阴极、阳极或假刺激配置的TDCS 20分钟之前、期间和之后进行一系列30次屈曲动作。阳极配置下肱二头肌的抑制性APAs和肱三头肌的兴奋性APAs均大于假刺激和阴极配置，而后两者之间未发现差异（阳极与假刺激相比：肱二头肌+26.5%，肱三头肌+66%；阳极与阴极相比：肱二头肌+20.5%，肱三头肌：+63.4%；对于两块肌肉，方差分析p<0.02，Tukey检验p<0.05）。相反，三角肌前部的APAs在所有配置中均未改变。原动肌募集和食指运动学未观察到变化。结果表明，SMA参与调节APAs的幅度。此外，TDCS对姿势和自主指令观察到的差异效应表明，运动程序的这两个成分在进入SMA之前就已经分开了。
