Ribot-Ciscar Edith, Bergenheim Mikael, Albert Frédéric, Roll Jean-Pierre
Laboratoire de Neurobiologie Humaine, UMR CNRS 6149 Neurobiologie Intégrative et Adaptative, Université de Provence, 52 Faculté des Sciences de Saint-Jérôme, Case 362, 13397 Marseille Cedex 20, France.
Exp Brain Res. 2003 Apr;149(4):512-9. doi: 10.1007/s00221-003-1384-x. Epub 2003 Feb 7.
The present study investigates the coding of positions reached in a two-dimensional space by populations of muscle spindle afferents. The unitary activity of 35 primary muscle spindle afferents originating from the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus lateralis muscles were recorded from the common peroneal nerve by the microneurographic technique. The steady mean frequency of discharge was analyzed during 16 passively maintained positions of the tip of the foot. These positions were equally distant from and circularly arranged around the "neutral" position of the ankle. The results showed that a same position of the foot was differently coded depending on whether it was maintained for several seconds or whether it was attained after a movement. Muscle spindle activity was increased or decreased, respectively, when the previous movement lengthened or shortened the parent muscle; the magnitude of change in activity depended on the amount of lengthening or shortening in relation to movement direction. Each muscle surrounding the ankle joint was shown to encode the different spatial positions following a directional tuning curve. Data were analyzed by using the "neuronal population vector model". This model consists of calculating population vectors representing the mean contribution of each muscle population of afferents to the coding of a particular position, and by finally calculating a sum vector. The direction of the sum vector was shown to accurately describe the direction of a given maintained position compared to the initial position. We conclude that muscle spindle position coding is based on afferent information coming from the whole set of muscles crossing a given joint. A given spatial position is associated with a stable muscle afferent inflow where each muscle makes an oriented and weighted contribution to its coding.
本研究调查了肌肉梭传入神经群体对二维空间中所到达位置的编码。通过微神经图技术从腓总神经记录了源自胫骨前肌、趾长伸肌、拇长伸肌和腓骨短肌的35条初级肌肉梭传入神经的单位活动。在足尖的16个被动维持位置期间分析了放电的稳定平均频率。这些位置与踝关节的“中立”位置等距且呈圆形排列。结果表明，相同的足部位置根据其是保持数秒还是在运动后达到而有不同的编码。当前一个运动使母肌伸长或缩短时，肌肉梭活动分别增加或减少；活动变化的幅度取决于相对于运动方向的伸长或缩短量。踝关节周围的每块肌肉都显示出遵循方向调谐曲线对不同空间位置进行编码。通过使用“神经元群体向量模型”对数据进行分析。该模型包括计算代表每个传入神经肌肉群体对特定位置编码的平均贡献的群体向量，并最终计算一个和向量。与初始位置相比，和向量的方向被证明能准确描述给定维持位置的方向。我们得出结论，肌肉梭位置编码基于来自跨越给定关节的整个肌肉组的传入信息。给定的空间位置与稳定的肌肉传入信息流相关联，其中每块肌肉对其编码做出定向且加权的贡献。
