Department of Neurology, School of Medicine, Fukushima Medical University, Fukushima, Japan.
Clin Neurophysiol. 2012 Jul;123(7):1415-21. doi: 10.1016/j.clinph.2011.11.037. Epub 2012 Jan 26.
Quadripulse transcranial magnetic stimulation (QPS) is a newly designed patterned repetitive transcranial magnetic stimulation (TMS). Previous studies of QPS showed bidirectional effects on the primary motor cortex (M1), which depended on its inter-stimulus interval (ISI): motor evoked potentials (MEPs) were potentiated at short ISIs and depressed at long ISIs (homotopic effects). These physiological characters were compatible with synaptic plasticity. In this research, we studied effects of QPS on the primary sensory cortex (S1).
One burst consisted of four monophasic TMS pulses at an intensity of 90% active motor threshold. The ISI of four pulses was set at 5 ms (QPS-5) or at 50 ms (QPS-50). Same bursts were given every 5s for 30 min. QPS-5 and QPS-50 were performed over three areas (M1, S1 and dorsal premotor cortex (dPMC)). One sham stimulation session was also performed. Excitability changes of S1 were evaluated by timeline of somatosensory evoked potentials (SEPs).
QPS-5 over M1 or dPMC enhanced the P25-N33 component of SEP, and QPS-50 over M1 depressed it. By contrast, QPSs over S1 had no effects on SEPs.
QPSs over motor cortices modulated the S1 cortical excitability (heterotopic effects). Mutual connections between dPMC or M1 and S1 might be responsible for these modulations.
QPSs induced heterotopic LTP or LTD-like cortical excitability changes.
四脉冲经颅磁刺激（QPS）是一种新设计的模式重复经颅磁刺激（TMS）。以前的 QPS 研究表明，它对初级运动皮层（M1）有双向影响，这取决于其刺激间隔（ISI）：在短 ISI 时运动诱发电位（MEP）增强，在长 ISI 时抑制（同域效应）。这些生理特征与突触可塑性相吻合。在这项研究中，我们研究了 QPS 对初级感觉皮层（S1）的影响。
一个爆发由四个单相 TMS 脉冲组成，强度为 90%主动运动阈值。四个脉冲的 ISI 设定为 5ms（QPS-5）或 50ms（QPS-50）。相同的爆发每 5 秒给予一次，持续 30 分钟。QPS-5 和 QPS-50 在三个区域（M1、S1 和背侧运动前皮层（dPMC））进行。还进行了一次假刺激会话。通过体感诱发电位（SEP）的时间线评估 S1 的兴奋性变化。
M1 或 dPMC 上的 QPS-5 增强了 SEP 的 P25-N33 成分，而 M1 上的 QPS-50 则抑制了它。相比之下，S1 上的 QPS 对 SEP 没有影响。
运动皮层上的 QPS 调节了 S1 皮层兴奋性（异域效应）。dPMC 或 M1 与 S1 之间的相互连接可能是这些调节的原因。
QPS 诱导了异域 LTP 或 LTD 样皮层兴奋性变化。
