Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany.
Department of Neurology, Assiut University Hospital, Assiut, Egypt.
Exp Brain Res. 2020 May;238(5):1305-1309. doi: 10.1007/s00221-020-05812-z. Epub 2020 Apr 22.
Cortical facilitation assessed with triad conditioning transcranial magnetic stimulation has been termed triad-conditioned facilitation (TCF). TCF has been supposed to reflect increased intracortical facilitation (ICF) at short interstimulus intervals (ISI) around 10 ms and an intrinsic rhythm of the motor cortex at longer ISI around 25 ms. To gain further insight into the pathophysiological mechanism of TCF, we systematically studied the effect of suprathreshold conditioning stimulus (CS) and test stimulus (TS) intensity on TCF. Various CS intensities and TS intensities were used in a triad-conditioning paradigm that was applied to 11 healthy subjects. ISI between pulses were studied between 5 and 200 ms. TCF at 10 ms ISI enhanced with increasing CS intensity but decreased with increasing TS intensity. The duration of facilitation was longer with higher CS intensity. However, TCF at 25 ms ISI could not be elicited with none of the CS and TS intensities addressed here. Our results are consistent with the notion of TCF at short ISI reflecting ICF. The enhanced and prolonged facilitation with increase of CS without additional isolated facilitation at longer ISI suggest a prolongation of ICF.
利用三刺激条件经颅磁刺激评估皮质易化被称为三刺激条件易化（TCF）。TCF 被认为反映了短刺激间隔（ISI）约 10ms 时的内皮质易化（ICF）增加，以及较长 ISI 约 25ms 时的运动皮层固有节律。为了更深入地了解 TCF 的病理生理机制，我们系统地研究了阈上条件刺激（CS）和测试刺激（TS）强度对 TCF 的影响。在 11 名健康受试者中应用三刺激条件范式，使用各种 CS 强度和 TS 强度。研究了脉冲之间的 ISI 在 5 至 200ms 之间。在 10ms ISI 时，随着 CS 强度的增加，TCF 增强，但随着 TS 强度的增加而降低。更高的 CS 强度导致易化持续时间更长。然而，这里研究的 CS 和 TS 强度均无法引发 25ms ISI 时的 TCF。我们的结果与短 ISI 时 TCF 反映 ICF 的观点一致。CS 增加时增强和延长的易化而没有更长 ISI 时的额外孤立易化提示 ICF 的延长。
