Arányi Zsuzsanna, Rösler Kai M
Department of Neurology, Semmelweis University Faculty of Medicine, Budapest, Hungary.
Exp Brain Res. 2002 Jul;145(1):76-82. doi: 10.1007/s00221-002-1101-1. Epub 2002 Apr 30.
During sustained, fatiguing maximal voluntary contraction of muscles of one hand, muscles of the other hand gradually become activated also. Such effort-induced mirror movements indicate a decreased ability of the central nervous system (CNS) to selectively control individual muscles. We studied whether altered transcallosal inhibition (TCI) contributed to this phenomenon. TCI was determined in ten healthy subjects by measuring the ipsilateral silent period (iSP) and the contralateral silent period (cSP) during a sustained contraction of the abductor digiti minimi, induced by focal unihemispheric ipsilateral transcranial magnetic stimulation. Mirror movements occurred in all subjects in response to the effort. There was a bilateral increase in cSPs and a parallel increase in the iSP in the contralateral working muscle. In contrast, the iSP in the mirroring muscle remained unchanged, explained by a balance of increased crossed pyramidal inhibition (cSP) and decreased transcallosal inhibition. In finely tuned unimanual movements, mirroring activity of the contralateral hand is suppressed by TCI originating in the working hemisphere. During sustained, effortful contractions, the outflow of the contralateral hemisphere is increased due to reduced TCI. Effort-induced mirror contractions are thus the result of disinhibition of contralateral crossed projections rather than disinhibition of ipsilateral uncrossed pathways.
在一只手的肌肉进行持续的、导致疲劳的最大自主收缩期间，另一只手的肌肉也会逐渐被激活。这种由努力诱发的镜像运动表明中枢神经系统（CNS）选择性控制单个肌肉的能力下降。我们研究了胼胝体间抑制（TCI）的改变是否导致了这一现象。通过在由局灶性单侧半球同侧经颅磁刺激诱发的小指展肌持续收缩期间测量同侧静息期（iSP）和对侧静息期（cSP），来确定10名健康受试者的TCI。所有受试者在用力时均出现了镜像运动。对侧工作肌肉的cSP出现双侧增加，同侧静息期（iSP）平行增加。相比之下，镜像肌肉中的iSP保持不变，这可以通过交叉锥体抑制增加（cSP）和胼胝体间抑制减少之间的平衡来解释。在精细协调的单手运动中，对侧手的镜像活动受到源自工作半球的TCI的抑制。在持续的、费力的收缩过程中，由于TCI减少，对侧半球的输出增加。因此，由努力诱发的镜像收缩是对侧交叉投射去抑制的结果，而不是同侧未交叉通路去抑制的结果。
