Triad TMS of Human Motor Cortex

Triad TMS of Human Motor Cortex

経頭蓋磁気刺激を用いて，ヒトの一次運動野の内的リズムに関する分析を施行した。閾値以下の3発刺激と閾値以上の試験刺激1発を一定の刺激間隔で与えたときの運動誘発電位の振幅を検討したところ，25ms間隔（すなわち40Hz）でのみ皮質内促通が誘発され，運動野のリズム特性との関係が推察された。神経疾患ではその促通の消失もしくはリズムの変化が生じており，本刺激法は，運動野のリズム特性を検討する1つの方法となる。

Abstract

To study cortical excitability changes induced by external stimulation with a certain rhythm, we developed a new method using motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) over the primary motor cortex. In this method, three conditioning TMS with the intensity below the motor threshold are given prior to the supra-threshold test stimulus with the four TMSs were separated by a certain interval (triad-conditioning stimulation: TCS). In healthy volunteers, MEP facilitation was elicited at an interval of 25ms, whereas TCSs with other intervals induced no facilitation. This frequency-dependent facilitation may reflect some intrinsic rhythm of M1 (25ms, i.e. 40Hz). In cortical myoclonus, the facilitation at 25ms was gone whereas facilitation was elicited by triad-conditioning stimulus at 40ms (25Hz), which is consistent with a previously reported abnormal beta rhythm in cortical myoclonus reported previously. Facilitation at 25ms was evoked in neither Parkinson's disease nor in amyotrophic lateral sclerosis. With TCS, we were able to investigate the intrinsic rhythmic activity of M1 and its changes in neurological disorders.