Taylor A, Ellaway P H, Durbaba R
Department of Sensorimotor Systems, Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, London W6 8RF, United Kingdom.
J Neurophysiol. 1998 Jul;80(1):130-42. doi: 10.1152/jn.1998.80.1.130.
A method is described for identifying the effect of single gamma static (gamma(s)) axons on bag2 or chain intrafusal fibers using random (Poisson-distributed) stimuli. The cross-correlogram of the stimuli with the firing of spindle primary afferents took one of three forms. A large, simple, brief response was taken to indicate pure chain fiber activation and a small, prolonged response to indicate pure bag2 activation. A compound response with brief and prolonged components was taken to be a sign of mixed innervation. The correlogram components could be well fitted with lognormal curves. They could also be transformed into curves of gain as a function of frequency, which were convenient for estimating the strength of the effects. In 68 effects of gammas axons on Ia afferents, 16 were pure chain, 17 pure bag2, and 35 mixed. This distribution was significantly different (P < 0. 05) from that expected from chance nonspecific innervation of chain and bag2 fibers. Making use of the estimates of the strength of chain and bag2 effects derived from the gain curves, the classification was modified by treating mixed responses that had one effect more than five times stronger than the other as belonging to the dominant type. The distribution was then as follows: chain 16, bag2 28, and mixed 24. This differed very significantly from the prediction of chance distribution (P < 0.001). This evidence for some degree of specific innervation of chain and bag2 fibers is discussed in relation to previous work and with regard to the ways in which the two fiber types might be used in natural movements.
本文描述了一种使用随机（泊松分布）刺激来识别单个γ静态（γ(s)）轴突对袋2或链内肌梭纤维影响的方法。刺激与梭内肌初级传入纤维放电的互相关图呈现三种形式之一。一个大的、简单的、短暂的反应被认为表明纯链纤维激活，一个小的、持续时间长的反应被认为表明纯袋2激活。一个具有短暂和持续成分的复合反应被认为是混合神经支配的标志。互相关图成分可以很好地用对数正态曲线拟合。它们也可以转换为增益随频率变化的曲线，这便于估计效应的强度。在γ轴突对Ia传入纤维的68次影响中，16次是纯链纤维激活，17次是纯袋2激活，35次是混合激活。这种分布与链纤维和袋2纤维随机非特异性神经支配预期的分布有显著差异（P < 0.05）。利用从增益曲线得出的链纤维和袋2纤维效应强度估计值，通过将一种效应比另一种效应强五倍以上的混合反应视为属于优势类型，对分类进行了修改。然后分布如下：链纤维激活16次，袋2激活28次，混合激活24次。这与随机分布的预测有非常显著的差异（P < 0.001）。本文结合先前的研究工作以及两种纤维类型在自然运动中可能的使用方式，讨论了链纤维和袋2纤维存在某种程度特异性神经支配的证据。
