Chen R, Yaseen Z, Cohen L G, Hallett M
Human Cortical Physiology Unit, Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
Ann Neurol. 1998 Sep;44(3):317-25. doi: 10.1002/ana.410440306.
We used transcranial magnetic stimulation (TMS) to study the time course of corticospinal excitability before and after brisk thumb abduction movements, either in a simple reaction time (RT) paradigm or self-paced. Premovement increase in corticospinal excitability began about 20 msec earlier for self-paced compared with simple RT movements. For both simple RT and self-paced movements after electromyographic (EMG) offset, there was a first period of increased excitability from 0 to 100 msec, followed by a second period from 100 to 160 msec. Corticospinal excitability was decreased from about 500 to 1,000 msec after EMG offset for both types of movements. Our results show that motor preparation that begins 1.5 to 2 seconds before self-paced movement is not associated with increased corticospinal excitability. The first phase of increased corticospinal excitability after EMG offset may be due to activity of motor cortex neuron subthreshold for activating spinal motor neurons, and the second phase may reflect a subthreshold second agonist burst. The period of decreased corticospinal excitability after movement corresponds to the onset of event-related synchronization (ERS) of electroencephalographic signals in the 20-Hz band, and supports the hypothesis that ERS may be related to an inactive, idling state of the motor cortex.
我们使用经颅磁刺激（TMS）来研究在快速拇指外展运动前后，皮质脊髓兴奋性的时间进程，实验采用简单反应时（RT）范式或自主节奏运动。与简单RT运动相比，自主节奏运动时皮质脊髓兴奋性的运动前增加开始时间提前约20毫秒。对于简单RT和自主节奏运动，在肌电图（EMG）信号结束后，都有第一个兴奋性增加期，从0到100毫秒，随后是第二个时期，从100到160毫秒。两种运动类型在EMG信号结束后约500到1000毫秒，皮质脊髓兴奋性均降低。我们的结果表明，在自主节奏运动前1.5到2秒开始的运动准备与皮质脊髓兴奋性增加无关。EMG信号结束后皮质脊髓兴奋性增加的第一阶段可能是由于运动皮层神经元的活动低于激活脊髓运动神经元的阈值，而第二阶段可能反映了低于阈值的第二激动剂爆发。运动后皮质脊髓兴奋性降低的时期与脑电图信号在20赫兹频段的事件相关同步（ERS）开始相对应，并支持ERS可能与运动皮层的非活动、闲置状态有关的假设。
