Meunier S, Pierrot-Deseilligny E
Laboratoire de Neurophysiologie Clinique, Rééducation, Hôpital de la Salpétrière, Paris, France.
Exp Brain Res. 1998 Apr;119(4):415-26. doi: 10.1007/s002210050357.
The effect of transcranial magnetic stimulation was investigated on presynaptic inhibition of Ia terminals in the human upper and lower limb. Presynaptic inhibition of Ia afferents was assessed by three different and independent methods: (1) heteronymous Ia facilitation of the H-reflex (assessing ongoing presynaptic inhibition of Ia afferents in the conditioning volley); (2) long-lasting inhibition of the H-reflex by a group I volley (D1 inhibition, assessing presynaptic inhibition on Ia afferents in the test volley); (3) measurement of the monosynaptic Ia peak evoked in single motor units by a homonymous or heteronymous volley (post stimulus time histogram method). The first two methods were used on the lower limb; the last two on the upper limb. Provided that the corticospinal volley and the explored Ia volley were directed to the same target motoneurones, cortical stimulation evoked significant and congruent changes: (1) In the lower limb, transcranial stimulation provided increased heteronymous Ia facilitation and decreased D1 inhibition, both of which suggest a decrease in presynaptic inhibition of Ia afferents; (2) in the upper limb, transcranial stimulation provided an increase in the radial-induced inhibition of the wrist flexor H-reflex and a decrease in the peak of monosynaptic Ia excitation in single units, both of which suggest an increase in presynaptic inhibition. Selectivity of corticospinal effects was explored by testing presynaptic inhibition of Ia afferents to soleus motoneurones and focusing the transcranial stimulation to excite preferentially different motor nuclei (soleus, quadriceps and tibialis anterior). A cortical-induced decrease in presynaptic inhibition of Ia afferents was seen when, and only when, cortical and peripheral Ia volleys were directed to the same motor nucleus.
研究了经颅磁刺激对人上肢和下肢Ia终末突触前抑制的影响。通过三种不同且独立的方法评估Ia传入纤维的突触前抑制：（1）H反射的异源Ia易化（评估条件波中Ia传入纤维正在进行的突触前抑制）；（2）I组波对H反射的长时抑制（D1抑制，评估测试波中Ia传入纤维的突触前抑制）；（3）通过同源或异源波刺激单个运动单位诱发的单突触Ia峰的测量（刺激后时间直方图法）。前两种方法用于下肢；后两种用于上肢。如果皮质脊髓波和所探究的Ia波指向同一目标运动神经元，则皮质刺激会引起显著且一致的变化：（1）在下肢，经颅刺激使异源Ia易化增加，D1抑制降低，这两者均提示Ia传入纤维的突触前抑制减少；（2）在上肢，经颅刺激使桡神经诱发的腕屈肌H反射抑制增加，单个运动单位的单突触Ia兴奋峰降低，这两者均提示突触前抑制增加。通过测试对比目鱼肌运动神经元Ia传入纤维的突触前抑制，并将经颅刺激聚焦于优先兴奋不同运动核（比目鱼肌、股四头肌和胫前肌），来探究皮质脊髓效应的选择性。仅当皮质和外周Ia波指向同一运动核时，才会出现皮质诱导的Ia传入纤维突触前抑制降低。
