Cash Robin F H, Dar Aisha, Hui Jeanette, De Ruiter Leo, Baarbé Julianne, Fettes Peter, Peters Sarah, Fitzgerald Paul B, Downar Jonathan, Chen Robert
Toronto Western Research Institute, University Health Network, University of Toronto, Canada; Monash Alfred Psychiatry Research Centre, Monash University Central Clinical School and The Alfred, Melbourne 3004, Australia.
MRI-Guided rTMS Clinic, Department of Psychiatry, University Health Network, Toronto, Canada.
Brain Stimul. 2017 May-Jun;10(3):630-636. doi: 10.1016/j.brs.2017.02.012. Epub 2017 Mar 2.
High frequency repetitive transcranial magnetic stimulation (rTMS) elicits plastic effects in excitatory and inhibitory circuits. Inter-train intervals (ITI) were initially incorporated into rTMS paradigms to avoid overheating and for safety considerations. Recent studies have shown that inclusion of ITI, as opposed to continuous stimulation, is essential for eliciting excitatory effects, but the optimal ITI remains unknown. Moreover, if ITI duration has no effect, it may be possible to substantially reduce treatment time for rTMS.
ITI duration modulates the excitatory and disinhibitory effects of rTMS.
rTMS (20 Hz, 2 s trains, 1200 pulses, 100% RMT) was applied in 14 healthy individuals with ITI of 4s (duration: ∼3 min), 8s (∼5 min), 16s (∼9 min) or 32s (16.5 min) in sessions separated by ≥5 days. Effects on cortical excitability and GABA receptor mediated short interval intracortical inhibition (SICI) were measured for 75 min following rTMS.
The time-course of increased cortical excitability following rTMS was independent of ITI duration. There was a striking influence of ITI on SICI, whereby disinhibition increased with shorter ITI duration. Changes in cortical excitability and SICI were independent of each other.
These findings provide the first evidence to suggest that ITI may be substantially shortened without loss of rTMS effects, and warrant further investigation where rTMS is applied therapeutically. Furthermore, shorter ITIs result in greater disinhibitory effects which may be desirable in some clinical disorders and accelerated treatment paradigms. The tuning of the plasticity of cortical excitatory and inhibitory circuits to rTMS parameters in human cortex are independent.
高频重复经颅磁刺激（rTMS）可在兴奋性和抑制性回路中引发可塑性效应。最初将串间间隔（ITI）纳入rTMS范式是为了避免过热并出于安全考虑。最近的研究表明，与连续刺激相反，纳入ITI对于引发兴奋效应至关重要，但最佳ITI仍然未知。此外，如果ITI持续时间没有影响，则有可能大幅缩短rTMS的治疗时间。
ITI持续时间调节rTMS的兴奋和去抑制作用。
对14名健康个体施加rTMS（20Hz，2秒串，1200个脉冲，100%静息运动阈值），ITI分别为4秒（持续时间：约3分钟）、8秒（约5分钟）、16秒（约9分钟）或32秒（16.5分钟），各疗程间隔≥5天。在rTMS后75分钟测量对皮质兴奋性和GABA受体介导的短间隔皮质内抑制（SICI）的影响。
rTMS后皮质兴奋性增加的时间进程与ITI持续时间无关。ITI对SICI有显著影响，即去抑制作用随ITI持续时间缩短而增加。皮质兴奋性和SICI的变化相互独立。
这些发现提供了首个证据，表明在不损失rTMS效果的情况下，ITI可能会大幅缩短，这值得在rTMS用于治疗时进行进一步研究。此外，较短的ITI会产生更大的去抑制作用，这在某些临床疾病和加速治疗范式中可能是可取的。人类皮质中皮质兴奋性和抑制性回路可塑性对rTMS参数的调节是相互独立的。
