Lüscher H R, Vardar U
Physiologisches Institute der Universität, Bern, Switzerland.
Exp Brain Res. 1989;74(3):480-92. doi: 10.1007/BF00247350.
Multi-unit spike triggered averaging was used to determine functional connectivity between spindle afferent fibers from the medial gastrocnemius muscle and the motoneurons innervating the medial (homonymous connections) and the lateral gastrocnemius-soleus muscle (heteronymous connections). As many as 288 possible connections between 24 motoneurons and 12 afferent fibers were studied in single, acute experiments. The influences of morphological and topographical factors, as well as of motoneuron species on functional connectivity were analysed. The probability that a motoneuron would receive functional connections from a given population of afferent fibers was related to its size and its proximity to the spinal entry level of the afferent fibers. The faster the axonal conduction velocity of the motoneuron (i.e. the larger the motoneuron) and the closer its location to the entry zone of the afferent fibers, the higher was its probability of receiving functional connections. The greater the conduction velocity (i.e. diameter) of a stretch receptor afferent fiber, the higher was its probability of making functional connections with motoneurons. These relationships were qualitatively similar for homonymous and heteronymous connections. 58% (233/399) of the Ia and group II afferents (combined) had functional connections with homonymous motoneurons, 32% (75/234) with heteronymous motoneurons. However, homonymous and heteronymous motoneurons of similar sizes were equally likely to receive functional connections when located at the same craniocaudal level. Differences in the locations and mean sizes of homonymous and heteronymous motoneurons however, cannot account completely for the observed overall differences in homonymous and heteronymous connectivity.
多单位锋电位触发平均法被用于确定来自内侧腓肠肌的梭传入纤维与支配内侧（同名连接）和外侧腓肠肌 - 比目鱼肌（异名连接）的运动神经元之间的功能连接。在单次急性实验中，研究了24个运动神经元和12条传入纤维之间多达288种可能的连接。分析了形态学和地形学因素以及运动神经元类型对功能连接的影响。运动神经元从给定传入纤维群体接收功能连接的概率与其大小以及与传入纤维脊髓入口水平的接近程度有关。运动神经元的轴突传导速度越快（即运动神经元越大）且其位置越靠近传入纤维的入口区域，其接收功能连接的概率就越高。牵张感受器传入纤维的传导速度（即直径）越大，其与运动神经元建立功能连接的概率就越高。这些关系在同名和异名连接中在质量上是相似的。58%（233/399）的Ia和II类传入纤维（合并）与同名运动神经元有功能连接，32%（75/234）与异名运动神经元有功能连接。然而，当位于相同的头尾水平时，大小相似的同名和异名运动神经元接收功能连接的可能性是相等的。然而，同名和异名运动神经元在位置和平均大小上的差异并不能完全解释观察到的同名和异名连接的总体差异。
