Gandevia S C, Rothwell J C
Department of Neurology, Prince Henry Hospital, Sydney, Australia.
Brain. 1987 Oct;110 ( Pt 5):1117-30. doi: 10.1093/brain/110.5.1117.
This study examined the extent to which subjects can direct internal motor commands to specific pools of motoneurons. These commands were subthreshold for muscle activity and were presumably not associated with any change in background afferent activity. Percutaneous stimuli were delivered to the motor cortex using the technique of Merton and Morton (1980) while the discharge of the first-recruited motor units from two intrinsic hand muscles was recorded with selective needle electrodes. In the absence of movement or detectable electromyographic activity subjects learned to focus their internal command upon one of the pair of hand muscles such that a liminal cortical stimulus activated motoneurons in the 'focused' but not the 'unfocused' muscle. This ability was not acquired for pairs of muscles in the forearm. When the cortical stimuli activated only one motor unit in a muscle, the same unit was the first recruited during a voluntary contraction. These results suggest that motor commands can be precisely monitored and fractionated for individual intrinsic muscles of the human hand without recourse to afferent feedback. This ability may be useful for organizing and learning fine manipulative tasks.
本研究考察了受试者能够将内部运动指令导向特定运动神经元池的程度。这些指令对于肌肉活动来说是阈下的，并且推测与背景传入活动的任何变化无关。使用默顿和莫顿（1980年）的技术将经皮刺激施加到运动皮层，同时用选择性针电极记录来自两块手部固有肌肉的最先募集的运动单位的放电情况。在没有运动或可检测到的肌电图活动的情况下，受试者学会将他们的内部指令集中在一对手部肌肉中的一块上，这样阈限皮层刺激会激活“聚焦”肌肉而非“未聚焦”肌肉中的运动神经元。对于前臂的肌肉对，这种能力并未获得。当皮层刺激仅激活一块肌肉中的一个运动单位时，该相同单位在自愿收缩期间是最先被募集的。这些结果表明，无需借助传入反馈，就可以对人类手部的单个固有肌肉的运动指令进行精确监测和细分。这种能力可能有助于组织和学习精细的操作任务。
