Klein Breteler Mary D, Simura Katarzyna J, Flanders Martha
Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
Cereb Cortex. 2007 Apr;17(4):803-15. doi: 10.1093/cercor/bhk033. Epub 2006 May 12.
Recent studies have described muscle synergies as overlapping, multimuscle groups defined by synchronous covariation in activation intensity. A different approach regards a synergy as a fixed temporal sequence of bursts of activity across groups of motoneurons. To pursue this latter definition, the present study used a principal component (PC) analysis tailored to reveal the across-muscle temporal synergies of human hand movement. Electromyographic (EMG) activity was recorded as subjects used a manual alphabet to spell a list of words. The analysis was applied to the EMG waveforms from 27 letter-to-letter transitions of equal duration. The first PC (of 27) represented the main temporal synergy; after practice, it began to account for more of the EMG variance (up to 40%). This main synergy began with a burst in the 4-finger extensor and a silent period in the flexors. There were then progressively later and shorter bursts in the thumb abductor, thumb flexor, little finger abductor, and finally the finger flexors. The results suggest that hand movements may be generated by activity waves unfolding in time. Because finger muscles are under relatively direct cortical control, this suggests a specific form of cortical pattern generation.
最近的研究将肌肉协同作用描述为通过激活强度的同步共变定义的重叠多肌肉群。另一种方法将协同作用视为运动神经元群之间活动爆发的固定时间序列。为了探究后一种定义，本研究使用了一种主成分（PC）分析方法，专门用于揭示人类手部运动的跨肌肉时间协同作用。当受试者使用手动字母表拼出一系列单词时，记录其肌电图（EMG）活动。该分析应用于来自27个等时长字母到字母转换的EMG波形。27个主成分中的第一个代表主要的时间协同作用；经过练习后，它开始解释更多的EMG方差（高达40%）。这种主要协同作用始于四指伸肌的一阵爆发以及屈肌的一段静息期。随后，拇外展肌、拇屈肌、小指外展肌以及最终的手指屈肌依次出现逐渐延迟且持续时间更短的爆发。结果表明，手部运动可能由随时间展开的活动波产生。由于手指肌肉受相对直接的皮质控制，这提示了一种特定形式的皮质模式生成。
