Department of Orthopaedic Surgery, Kochi Medical School, Kohasu Oko-cho, Nankoku-shi, Kochi 783-8505, Japan.
Clin Neurophysiol. 2011 Jul;122(7):1405-10. doi: 10.1016/j.clinph.2010.12.041. Epub 2011 Jan 21.
To test if simple motor imagery, like thumb abduction, preferentially influences the excitability of the spinal or cortical motoneurons.
Ten healthy subjects underwent two separate experiments, each consisting of recording F waves and MEPs from abductor pollicis brevis (APB) in three consecutive sessions: (1) baseline, (2) after immobilizing APB for 3 h, and (3) after brief muscle exercise. During the immobilization, the subjects were instructed to volitionally relax APB in experiment 1 (relaxation task), and mentally simulate thumb abduction without actual movement in experiment 2 (imagery task).
Relaxation task suppressed both MEPs and F waves. Motor imagery reduced this suppression, restoring F waves nearly completely (94%) and MEPs only partially (77%). Hence, the rest-induced decline of MEPs in part results from cortical modulation. In contrast, statistical analysis revealed no differences in imagery-induced recovery of motoneuron excitabilities whether assessed by F wave or MEP. Thus, increased excitability of spinal motoneurons responsible for F-wave changes also accounts for recovery of MEPs.
Volitional relaxation depresses the spinal and cortical motoneurons, whereas mental simulation counters rest-induced suppression primarily by restoring spinal excitability.
The present findings help elucidate physiologic mechanisms underlying motor imagery.
测试简单的运动想象，如拇指外展，是否优先影响脊髓或皮质运动神经元的兴奋性。
10 名健康受试者接受了两项独立的实验，每个实验都包括在三个连续的会话中记录拇短展肌（APB）的 F 波和 MEP：（1）基线，（2）APB 固定 3 小时后，和（3）短暂的肌肉运动后。在固定期间，在实验 1 中（放松任务），受试者被指示主动放松 APB，在实验 2 中（想象任务），不进行实际运动，而是精神模拟拇指外展。
放松任务抑制了 MEP 和 F 波。运动想象减轻了这种抑制，几乎完全恢复了 F 波（94%），但仅部分恢复了 MEP（77%）。因此，MEP 的休息诱导下降部分是由于皮质调制。相比之下，统计分析显示，无论通过 F 波还是 MEP 评估，想象引起的运动神经元兴奋性恢复都没有差异。因此，负责 F 波变化的脊髓运动神经元兴奋性的增加也解释了 MEP 的恢复。
自愿放松会抑制脊髓和皮质运动神经元，而精神模拟主要通过恢复脊髓兴奋性来对抗休息引起的抑制。
本研究结果有助于阐明运动想象的生理机制。
