Mathis J, Gurfinkel V S, Struppler A
Department of Neurology, University Hospital, Bern, Switzerland.
Electroencephalogr Clin Neurophysiol. 1996 Aug;101(4):289-97. doi: 10.1016/0924-980x(96)95599-x.
We have applied repeated transcranial magnetic stimuli during the involuntary postcontraction muscle activity (Kohnstamm phenomenon) or during a tonic vibration reflex, both presumably arising from subcortical levels. The motor evoked potentials (MEPs) were compared with the MEPs evoked during a comparable voluntary contraction (cortical origin). The MEP amplitudes from the deltoid muscle appeared linearly related to the mean amplitude of the smoothed rectified background EMG preceding the stimulus. No differences in the facilitatory effect between voluntary and involuntary preinnervation manoeuvres were found. If we accept the hypothesis of a subcortical origin of the involuntary muscle activity in the Kohnstamm phenomenon, the similar facilitatory effect of involuntary and voluntary background EMG supports a predominantly spinal localisation of the facilitatory mechanism in this proximal muscle both during involuntary and during voluntary activity, at least under the present conditions of rather low stimulus strengths. In about 20-30% of all the trials an extra facilitatory effect on the MEP amplitude was observed during the shortening contraction compared to an MEP elicited during the lengthening contraction, in spite of a similar background EMG. This extra facilitatory effect of the shortening contraction was observed during involuntary and voluntary preactivation, suggesting an elevated excitatory state at the spinal level.
我们在非自主收缩后肌肉活动（科恩斯塔姆现象）期间或强直振动反射期间施加重复经颅磁刺激，这两种情况推测都源自皮质下水平。将运动诱发电位（MEP）与在类似自主收缩（皮质起源）期间诱发的MEP进行比较。三角肌的MEP波幅似乎与刺激前经平滑整流的背景肌电图的平均波幅呈线性相关。未发现自主和非自主预兴奋操作之间的易化作用存在差异。如果我们接受科恩斯塔姆现象中非自主肌肉活动源自皮质下的假说，那么非自主和自主背景肌电图的类似易化作用支持了在非自主和自主活动期间，至少在当前较低刺激强度的条件下，这种近端肌肉中易化机制主要定位于脊髓。在所有试验中，约20% - 30%的情况下，尽管背景肌电图相似，但与延长收缩期间诱发的MEP相比，缩短收缩期间观察到对MEP波幅有额外的易化作用。在非自主和自主预激活期间均观察到缩短收缩的这种额外易化作用，提示脊髓水平的兴奋状态升高。
