Hilgevoord A A, Bour L J, Koelman J H, Ongerboer de Visser B W
Graduate School Neurosciences Amsterdam, The Netherlands.
Electroencephalogr Clin Neurophysiol. 1995 Dec;97(6):402-7. doi: 10.1016/0924-980x(95)00174-j.
Extinction of the soleus H reflex at higher stimulus intensities is commonly attributed to retrograde conduction of action potentials in motor axons. This study was designed to gain further insight into the mechanisms underlying the extinction. The decrease of the H reflex was quantified in a group of controls and spastic patients, with and without depression of the H response by continuous tendon vibration. Response amplitudes were normalized as a percentage of the maximal M wave amplitude. Stimuli were normalized as a multiple of the M wave threshold. After normalization, the mean M recruitment curves, and similarly the fractions of motor axons activated, were equal in each group. In contrast, the mean H reflex amplitudes at the M threshold were different. The mean H reflex decrease, between 1.0 and 1.5 times the M threshold, was found to be the same fraction of the maximal H reflex amplitude in each group. The largest motor fibres, belonging to the largest motoneurones, are traditionally thought to have the lowest threshold for electrical excitation. Collision or retrograde inactivation should therefore preferentially affect the largest motoneurones, employed in only the largest H reflexes, at the lowest stimulus intensities. Our results are contrary to this hypothesis. Renshaw and/or Ib inhibition is likely to play a role in the initial decrease of the H reflex at higher stimulus intensities.
比目鱼肌H反射在较高刺激强度下的消退通常归因于运动轴突中动作电位的逆行传导。本研究旨在进一步深入了解消退背后的机制。在一组对照组和痉挛患者中，量化H反射的降低情况，这些患者在有或没有通过持续肌腱振动使H反应降低的情况下进行检测。反应幅度以最大M波幅度的百分比进行归一化。刺激强度以M波阈值的倍数进行归一化。归一化后，每组的平均M募集曲线以及同样被激活的运动轴突比例均相等。相比之下，在M阈值时的平均H反射幅度不同。发现在每组中，刺激强度在1.0至1.5倍M阈值之间时，平均H反射降低幅度占最大H反射幅度的比例相同。传统观点认为，属于最大运动神经元的最大运动纤维对电刺激的阈值最低。因此，碰撞或逆行失活应优先影响仅在最低刺激强度下参与最大H反射的最大运动神经元。我们的结果与这一假设相反。在较高刺激强度下，闰绍和/或Ib抑制可能在H反射的初始降低中起作用。
