Drews H, Gerilovsky L, Studer L M, Ruegg D G
Institute of Physiology, University of Fribourg, Switzerland.
Somatosens Mot Res. 1998;15(2):109-17. doi: 10.1080/08990229870835.
Electrical stimuli were applied to the tibial nerve in the popliteal fossa in man in order to investigate how information is transferred from group I muscle afferents to motoneurons and to the somatosensory cortex. For control purposes, identical stimuli were applied to the skin beside the electrode above the nerve. The somatosensory evoked potential (SEP) to skin stimulation alone had a peak latency which was 5 ms longer than the SEP to transcutaneous nerve stimulation. Influences by stimulation of the skin above the nerve could thus be excluded. The threshold intensity to evoke a liminal H reflex was at least two times higher than the threshold for a SEP. In most of the subjects, there was a correlation between the H reflex and the SEP size. If two identical stimuli were applied to the posterior tibial nerve with an interval of 1 s, the second H reflex was 30% smaller than the first one (postactivation depression). The corresponding SEPs were, however, only slightly reduced. Postactivation depression was probably caused by general intrinsic properties of synapses of group I muscle afferents. The results of this investigation indicate that: (1) a large volley in group I muscle afferents is necessary to evoke a liminal H reflex, whereas transmission from muscle afferents to the somatosensory cortex is very efficient; (2) these feedback signals to motoneurons and the somatosensory cortex are used independently.
为了研究信息是如何从I类肌肉传入神经传递到运动神经元和躯体感觉皮层的，对人体腘窝处的胫神经施加电刺激。作为对照，在神经上方电极旁边的皮肤施加相同的刺激。单独对皮肤刺激的体感诱发电位（SEP）的峰值潜伏期比经皮神经刺激的SEP长5毫秒。因此可以排除神经上方皮肤刺激的影响。诱发阈下H反射的阈强度至少比SEP的阈强度高两倍。在大多数受试者中，H反射和SEP大小之间存在相关性。如果以1秒的间隔对胫后神经施加两个相同的刺激，第二个H反射比第一个小30%（激活后抑制）。然而，相应的SEP只是略有降低。激活后抑制可能是由I类肌肉传入神经突触的一般内在特性引起的。这项研究的结果表明：（1）I类肌肉传入神经中的大量冲动对于诱发阈下H反射是必要的，而从肌肉传入神经到躯体感觉皮层的传递非常有效；（2）这些向运动神经元和躯体感觉皮层的反馈信号是独立使用的。
