Roll J P, Bergenheim M, Ribot-Ciscar E
Laboratoire de Neurobiologie Humaine, UMR 6562, Université de Provence/CNRS, Marseille, France.
Exp Brain Res. 2000 Oct;134(3):311-21. doi: 10.1007/s002210000472.
It was proposed to study the proprioceptive sensory coding of movement trajectories during the performance of two-dimensional "drawing-like" movements imposed on the tip of the foot. For this purpose, the activity of the muscle-spindle afferents from the Extensor digitorum longus, Tibialis anterior, Extensor hallucis longus, and Peroneus lateralis muscles was recorded from the lateral peroneal nerve using the microneurographic technique. The drawing movements, describing geometrical shapes such as squares, triangles, ellipses, and circles, were imposed at a constant velocity in both the clockwise and counterclockwise directions. A total number of 44 muscle-spindle afferents were tested, 36 of which were identified as primary and eight as secondary afferents. Whatever the shape of the imposed foot movement, the primary endings from one muscle never discharged throughout the whole trajectory (on average, they discharged for only 49.2% of the length of the trajectory), whereas all the secondary endings discharged for most part of the drawing trajectories (average: 84.8%). The relationship between afferent discharge rate and direction could be described with a cosine-shaped tuning function. The peak of this function corresponded to the preferred sensory direction of the receptor-bearing muscles. The whole path of a given geometrical drawing movement was found to be coded in turn by each of the primary afferents originating from each of the muscles successively stretched. The contribution of each population of muscle afferents from each ankle muscle was represented by a "population vector", whose orientation was the preferred direction of the muscle under consideration and whose length was the mean instantaneous frequency of the afferent population. The "sum vector" corresponding to the sum of all these weighted "population vectors" was found to point in the instantaneous direction of the drawing trajectory, i.e., the tangent to the trajectory. These findings suggest that trajectory information is already encoded at the peripheral level on the basis of the integrated inputs provided by sets of receptors belonging to all the muscles acting on a given joint.
有人提议研究在施加于脚尖的二维“绘图样”运动执行过程中运动轨迹的本体感觉编码。为此，使用微神经图技术从腓总外侧神经记录来自趾长伸肌、胫骨前肌、拇长伸肌和腓骨短肌的肌梭传入纤维的活动。描述正方形、三角形、椭圆形和圆形等几何形状的绘图运动以恒定速度在顺时针和逆时针方向上进行。总共测试了44条肌梭传入纤维，其中36条被鉴定为初级传入纤维，8条为次级传入纤维。无论施加的足部运动形状如何，来自一块肌肉的初级末梢在整个轨迹中都不会全程放电（平均而言，它们仅在轨迹长度的49.2% 时间内放电），而所有次级末梢在绘图轨迹的大部分时间内都会放电（平均：84.8%）。传入放电率与方向之间的关系可用余弦形调谐函数来描述。该函数的峰值对应于含感受器肌肉的首选感觉方向。发现给定几何绘图运动的整个路径依次由源自相继被拉伸的每块肌肉的每条初级传入纤维进行编码。来自每个踝关节肌肉的每组肌传入纤维的贡献由一个“群体向量”表示，其方向是所考虑肌肉的首选方向，其长度是传入群体的平均瞬时频率。发现对应于所有这些加权“群体向量”之和的“和向量”指向绘图轨迹的瞬时方向，即轨迹的切线方向。这些发现表明，轨迹信息已经在周边水平上基于作用于给定关节的所有肌肉所属的感受器集合提供的综合输入进行编码。
