Reynolds C, Ashby P
The Toronto Hospital, Western Division, University of Toronto, Ontario, Canada.
Neurology. 1999 Sep 11;53(4):730-5. doi: 10.1212/wnl.53.4.730.
To examine inhibition in the human motor cortex before and during voluntary movements.
The balance between the excitation and inhibition of corticospinal neurons in the human motor cortex was tested by conditioning the motor evoked potentials (MEP) evoked in forearm muscles by transcranial magnetic stimulation with a preceding subthreshold stimulus delivered through the same coil.
When normal individuals (n = 9) made a tonic wrist extension, inhibition of the forearm extensor MEP decreased, whereas that of the forearm flexors was unchanged. When these individuals made a tonic wrist flexion, inhibition of the forearm flexor MEP diminished, whereas that of the forearm extensors was unchanged. When normal individuals (n = 10) made a phasic wrist extension in response to an auditory signal, inhibition of the extensor MEP began to decline about 95 msec before the onset of the agonist EMG activity.
The changes in balance of excitation and inhibition of corticospinal neurons associated with a voluntary movement precede the movement and are directed at the corticospinal neurons projecting to the agonists. These changes may help to select the population of cortical neurons responsible for the movement.
研究人类运动皮层在自主运动之前及运动过程中的抑制作用。
通过经颅磁刺激诱发前臂肌肉运动诱发电位（MEP），并在同一线圈施加阈下刺激作为条件刺激，以此来测试人类运动皮层中皮质脊髓神经元兴奋与抑制之间的平衡。
正常个体（n = 9）进行持续性腕伸展时，前臂伸肌MEP的抑制作用减弱，而前臂屈肌的抑制作用不变。当这些个体进行持续性腕屈曲时，前臂屈肌MEP的抑制作用减弱，而前臂伸肌的抑制作用不变。正常个体（n = 10）对听觉信号做出阶段性腕伸展动作时，伸肌MEP的抑制作用在主动肌肌电图活动开始前约95毫秒开始下降。
与自主运动相关的皮质脊髓神经元兴奋与抑制平衡的变化先于运动发生，且针对投射至主动肌的皮质脊髓神经元。这些变化可能有助于选择负责该运动的皮层神经元群体。
