Monash Alfred Psychiatry Research Centre, Monash University, Central Clinical School and The Alfred, Melbourne, Australia.
Brain and Mental Health Laboratory, School of Psychological Sciences and Monash Biomedical Imaging, Monash Institute of Cognitive and Clinical Neuroscience, Monash University, Melbourne, Australia.
Hum Brain Mapp. 2018 Feb;39(2):783-802. doi: 10.1002/hbm.23882. Epub 2017 Nov 9.
Intermittent theta burst stimulation (iTBS) is a noninvasive brain stimulation technique capable of increasing cortical excitability beyond the stimulation period. Due to the rapid induction of modulatory effects, prefrontal application of iTBS is gaining popularity as a therapeutic tool for psychiatric disorders such as depression. In an attempt to increase efficacy, higher than conventional intensities are currently being applied. The assumption that this increases neuromodulatory may be mechanistically false for iTBS. This study examined the influence of intensity on the neurophysiological and behavioural effects of iTBS in the prefrontal cortex. Sixteen healthy participants received iTBS over prefrontal cortex at either 50, 75 or 100% resting motor threshold in separate sessions. Single-pulse TMS and concurrent electroencephalography (EEG) was used to assess changes in cortical reactivity measured as TMS-evoked potentials and oscillations. The n-back task was used to assess changes in working memory performance. The data can be summarised as an inverse U-shape relationship between intensity and iTBS plastic effects, where 75% iTBS yielded the largest neurophysiological changes. Improvement in reaction time in the 3-back task was supported by the change in alpha power, however, comparison between conditions revealed no significant differences. The assumption that higher intensity results in greater neuromodulatory effects may be false, at least in healthy individuals, and should be carefully considered for clinical populations. Neurophysiological changes associated with working memory following iTBS suggest functional relevance. However, the effects of different intensities on behavioural performance remain elusive in the present healthy sample.
经颅磁刺激（TMS）是一种非侵入性的大脑刺激技术，能够在刺激期之外增加皮质兴奋性。由于其快速诱导调制效应，额前应用 TMS 作为治疗抑郁症等精神障碍的工具越来越受到关注。为了提高疗效，目前正在应用高于传统强度的 TMS。假设这种方法可以增加神经调制，但对于 TBS 来说，这种假设在机制上可能是错误的。本研究探讨了强度对前额叶皮层 TBS 神经生理和行为效应的影响。16 名健康参与者在不同的治疗阶段分别接受了前额叶皮层的 TBS 刺激，刺激强度分别为 50%、75%和 100%的静息运动阈值。使用单脉冲 TMS 和同时进行的脑电图（EEG）来评估 TMS 诱发电位和振荡测量的皮质反应变化。使用 n-back 任务评估工作记忆性能的变化。数据可以总结为强度与 TBS 塑性效应之间的倒 U 形关系，其中 75%的 TBS 产生最大的神经生理变化。在 3-back 任务中的反应时间的改善得到了 alpha 功率变化的支持，然而，条件之间的比较没有显示出显著差异。高强度导致更大的神经调制效应的假设可能是错误的，至少在健康个体中是如此，对于临床人群应该谨慎考虑。TBS 后与工作记忆相关的神经生理变化表明其具有功能相关性。然而，在当前的健康样本中，不同强度对行为表现的影响仍然难以捉摸。
