Chanaud C M, Macpherson J M
Laboratory of Neural Control, National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Exp Brain Res. 1991;85(2):271-80. doi: 10.1007/BF00229406.
The biceps femoris (BF) muscle is divided into three neuromuscular compartments defined by the innervation patterns of the main nerve branches (English and Weeks 1987). The goals of this study were i) to determine how different regions of the biceps femoris muscle are activated in the intact cat during a broad range of limb movements evoked by perturbations of stance posture, and ii) to determine the relationship between the anatomical compartments of biceps femoris and the functional units as defined in this task. Cats were trained to stand on a moveable platform with each paw on a triaxial force plate. The animal's stance was perturbed by linear translation of the platform in each of sixteen different directions in the horizontal plane. EMG activity was recorded from eight sites across the width of the left biceps femoris muscle. During quiet stance only the anterior compartment was tonically active, presumably contributing to hip extensor torque in the maintenance of stance. During platform translation, evoked EMG activity was recorded from each electrode pair for a wide range of directions of perturbation; as direction changed progressively, the amplitude of evoked activity from any electrode pair increased to a maximum and then decreased. When the EMG amplitude was plotted in polar coordinates as a function of translation direction, the region of response formed a petal shaped area in the horizontal plane, termed the EMG tuning curve. The compartments of the BF muscle were not activated homogeneously. The tuning curve of the anterior BF compartment was similar to that of other hip extensors, and coincided with the region of postero-lateral force production by the hindlimb against the support. The tuning curve of the middle BF compartment was shifted in a counterclockwise direction from that of the anterior compartment, but overlapped extensively with it; the middle BF tuning curve was similar to that of anterior gracilis. The tuning curve of the posterior biceps compartment was rotated further counterclockwise and overlapped very little with that of the middle BF compartment. The posterior BF was activated in a pattern similar to that of other knee flexors. The functional units of BF activation were not identical with the neuromuscular compartments defined by the main nerve branches. As direction of the perturbation changed, the region of BF that was activated moved progressively across the muscle. This progression of the active region was continuous across BFa and BFm, whereas there was a jump, or discontinuity at the border between BFm and BFp.(ABSTRACT TRUNCATED AT 400 WORDS)
股二头肌（BF）分为三个神经肌肉区，由主要神经分支的支配模式界定（English和Weeks，1987年）。本研究的目的是：i）确定在因姿势扰动引起的广泛肢体运动过程中，完整猫体内股二头肌的不同区域是如何被激活的；ii）确定股二头肌的解剖分区与本任务中定义的功能单元之间的关系。训练猫站在一个可移动平台上，每只爪子放在一个三轴力板上。通过在水平面的十六个不同方向上线性平移平台来扰动动物的姿势。从左股二头肌宽度上的八个部位记录肌电图（EMG）活动。在安静站立时，只有前区持续活跃，推测这有助于维持站立时的髋伸肌扭矩。在平台平移过程中，针对广泛的扰动方向记录每个电极对诱发的EMG活动；随着方向逐渐改变，任何电极对诱发活动的幅度先增加到最大值然后减小。当以极坐标绘制EMG幅度作为平移方向的函数时，响应区域在水平面形成一个花瓣形区域，称为EMG调谐曲线。股二头肌的各区域并非均匀激活。股二头肌前区的调谐曲线与其他髋伸肌相似，并且与后肢向后外侧支撑产生力的区域一致。股二头肌中区的调谐曲线相对于前区逆时针方向偏移，但与之广泛重叠；股二头肌中区的调谐曲线与股薄肌前部相似。股二头肌后区的调谐曲线进一步逆时针旋转，与股二头肌中区的调谐曲线几乎没有重叠。股二头肌后区的激活模式与其他膝关节屈肌相似。股二头肌激活的功能单元与由主要神经分支界定的神经肌肉区并不相同。随着扰动方向的改变，股二头肌被激活的区域在肌肉上逐渐移动。活跃区域的这种移动在股二头肌前区（BFa）和中区（BFm）是连续的，而在股二头肌中区和后区（BFp）之间的边界处存在跳跃或不连续性。（摘要截取自400字）
