Preconditioning human pharyngeal motor cortex enhances directional metaplasticity induced by repetitive transcranial magnetic stimulation
Preconditioning human pharyngeal motor cortex enhances directional metaplasticity induced by repetitive transcranial magnetic stimulation
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DOI：
10.1113/jp279977
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发表时间：
2020-09-03
影响因子：
5.5
通讯作者：
Hamdy, Shaheen
中科院分区：
文献类型：
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作者：
Cheng, Ivy;Scarlett, Honor;Hamdy, Shaheen
关键点最近的研究提出了重复经颅磁刺激（rTMS）在吞咽康复中的治疗潜力，但其结果因个体和研究而异。这种变化可能与刺激前的大脑状态有关。元可塑性是一种高阶可塑性，它调节大脑皮层对可塑性变化的反应。研究表明，手部运动皮层的预处理可以增加皮层神经可塑性变化的能力，并增强rTMS的结果。我们调查，第一次，在人类咽运动皮层的定向化生特性，使用预处理rTMS。我们发现，在预处理和条件性rTMS之间有特定时间间隔的预处理rTMS在吞咽神经生理和行为方面都比没有预处理的rTMS具有更强的刺激效应。我们的研究结果为增强咽运动皮层的方向性超可塑性提供了证据，并为吞咽困难的临床应用提供了新的见解。尽管越来越多的证据表明重复经颅磁刺激（rTMS）可用于治疗吞咽困难，但其疗效因个体而异。这种可变性可能与神经元激活的预刺激状态有关。先前的研究发现，在rTMS之前对手部运动皮层进行预处理可以通过后可塑性增强刺激结果。没有研究调查在人类咽运动皮层的这种机制。因此，我们研究了rTMS对吞咽神经生理和行为的预处理作用。招募健康成人进行吞咽神经生理学（n = 14）和行为学（n = 14）实验。他们首先给予8种不同的预处理（1和5 Hz）rTMS干预与不同的inter-rTMS间隔。在rTMS之前和之后60分钟测量运动诱发电位（MEP）。根据咽部MEP的变化，然后应用最佳预处理的1 Hz和5 Hz rTMS方案作为干预措施，同时使用反应时间任务评估吞咽性能。结果发现，5 Hz rTMS预处理组与1Hz rTMS预处理组（rTMS间隔30 min），咽部皮层兴奋性增加最明显（F-1，F-13 = 21.244;P < 0.001）。相比之下，1 Hz rTMS预处理与5 Hz rTMS，90 min间隔的rTMS抑制咽运动皮层最佳（F-1，F-13 = 13.547;P = 0.003）。在行为学上，与假手术组相比，预处理5 Hz rTMS后吞咽准确性提高（F-1，F-13 = 10.109，P = 0.007），预处理1 Hz rTMS后吞咽准确性降低（F-1，F-13 = 14.108，P = 0.009）。因此，两个最佳的协议，诱导人咽部运动皮层的功能性后可塑性已被确定。这些协议出现上级传统的rTMS，并可能与未来的临床应用在神经源性吞咽困难。
Key pointsRecent studies have proposed therapeutic potential for repetitive transcranial magnetic stimulation (rTMS) in swallowing rehabilitation, yet its outcomes vary across individuals and studies. Such variability may be related to the brain state before stimulation. Metaplasticity is a higher order plasticity which regulates cortical response to plasticity changes. Studies have shown that preconditioning of the hand motor cortex could increase cortical capacity for neuroplastic change and enhance rTMS outcomes. We investigated, for the first time, the directional metaplastic properties in human pharyngeal motor cortex using preconditioned rTMS. We found that preconditioned rTMS with specific time intervals between preconditioning and conditioning rTMS had stronger stimulation effects in both swallowing neurophysiology and behaviour than that without preconditioning. Our results provide evidence for enhanced directional metaplasticity in pharyngeal motor cortex and new insights into its clinical application for dysphagia. Despite growing evidence that repetitive transcranial magnetic stimulation (rTMS) can be used as a treatment for dysphagia, its efficacy varies across individuals. Such variability may relate to the pre-stimulation state of neuronal activation. Previous studies found that preconditioning the hand motor cortex before rTMS could enhance stimulation outcomes through metaplasticity. No studies have investigated such mechanisms in human pharyngeal motor cortex. Therefore, we investigated the preconditioning effects of rTMS on swallowing neurophysiology and behaviour. Healthy adults were recruited for swallowing neurophysiological (n = 14) and behavioural (n = 14) experiments. They were first given eight different preconditioned (1 and 5 Hz) rTMS interventions with varying inter-rTMS intervals. Motor evoked potentials (MEPs) were measured before and for 60 min post-rTMS. Based on the changes in pharyngeal MEPs, the optimal preconditioned 1 Hz and 5 Hz rTMS protocols were then applied as interventions while assessing swallowing performance using a reaction time task. We found that 5 Hz rTMS preconditioned with 1 Hz rTMS with 30 min inter-rTMS interval induced the greatest increase on pharyngeal cortical excitability (F-1,F-13 = 21.244;P < 0.001). By comparison, 1 Hz rTMS preconditioned with 5 Hz rTMS with 90 min inter-rTMS interval was most optimal for suppressing pharyngeal motor cortex (F-1,F-13 = 13.547;P = 0.003). Behaviourally, swallowing accuracy was improved after preconditioned 5 Hz rTMS (F-1,F-13 = 10.109,P = 0.007) and reduced after preconditioned 1 Hz rTMS (F-1,F-13 = 14.108,P = 0.009) compared to sham. Thus, two optimal protocols for inducing functional metaplasticity in human pharyngeal motor cortex have been identified. These protocols appear superior to conventional rTMS and may be relevant to future clinical application in neurogenic dysphagia.