經皮迷走神經電刺激對有、無焦慮症狀巴金森患者重心轉移控制的影響：於不同轉移速度下討論

Abstract

背景與研究目的：良好的重心轉移為巴金森患者姿勢控制的重要因素之一，尤其在快速移動下，正確的重心轉移可降低跌倒發生率。除動作症狀，焦慮問題亦會惡化巴金森患者姿勢平衡控制能力。經皮迷走神經刺激為一種降低焦慮的神經電刺激介入法，然而目前尚無研究探討巴金森患者在不同姿勢動作速度下，經皮迷走神經電刺激對焦慮與姿勢控制的影響。本研究目的為探討經皮迷走神經電刺激是否有助於巴金森患者焦慮程度降低與提升不同速度下重心轉移控制表現，並探討其相對應之大腦皮質活動變化。 方法：本研究共招募15名患具焦慮症狀的巴金森患者與15名不具焦慮症狀的巴金森患者。每位受試者分別於接受主動經皮迷走神經電刺與假性經皮迷走神經電刺下，站立於力板進行不同節律重心轉移動作，分別為：慢速(0.25 Hz)、中速(0.33 Hz)、快速(0.50 H)，於重心轉移動作過程中，同時量測皮膚電導訊號與腦電圖訊號。主要參數為：重心轉移軌跡誤差量、重心轉移軌跡急動值、重心轉移幅度、、各頻帶大腦活動強度、動作時主觀與客觀焦慮程度。除主觀焦慮程度採無母數分析，其餘參數以2×2混合變異數分析(2×2 mixed ANOVA)與邦佛洛尼校正(Bonferroni correction)進行事後檢定，分析主動、假性迷走神經電刺激對有焦慮組、無焦慮組於各重心轉移速度下，各行為表現參數及腦電圖頻譜強度的影響。 結果：於行為表現上，僅有焦慮組在接受迷走神經刺激時，於各種速度情境下皆可顯著降低重心轉移軌跡誤差量與增加重心轉移軌跡急動值，非焦慮組的行為表現則在中速(0.33 Hz)情境下，給予迷走神經刺激反而降低重心轉移幅度。於慢速與中速情境下，焦慮組比起非焦慮組有更高的主觀焦慮強度。無論重心轉移運動的速度如何，焦慮組在前額葉、額葉、感覺運動、頂葉-枕葉皮質區的theta波和alpha波功率都較非焦慮組高；相反的，非焦慮組在感覺動作區有較高的的high gamma頻帶功率。而經皮迷走神經電刺激對腦電圖相對功率的調節主要影響在較慢的速度情境(0.25 Hz與 0.33 Hz)。經皮迷走神經刺激會增加非焦慮患者前額葉區delta與降低high gamma頻帶強度，並降低焦慮患者額葉區low gamma頻帶強度。 結論：短時間的經皮迷走神經電刺激可改善具有焦慮症狀的巴金森患者的重心轉移控制表現，並在較慢的重心轉移速度上呈現大腦活動調節。於臨床上可利用經皮迷走神經促進巴金森患者重心轉移表現。本研究並無發現經皮迷走神經電刺激對焦慮程度的效果，未來可探討經皮迷走神經刺激的長時間介入效果，以更完整探討經皮迷走神經刺激對巴金森患者平衡控制、焦慮調節與大腦活動之效益。

Background and purpose: Effective weight-shifting is a crucial factor in posture control for people with Parkinson's disease (PD), especially during rapid movements, as proper weight-shifting could reduce fall incidence. In addition to motor symptoms, anxiety would deteriorate posture control in people with PD. Transcutaneous vagus nerve stimulation (tVNS) is a neuroelectric intervention which has been used to reduce anxiety. However, no studies have explored the impact of tVNS on anxiety and posture control in at different movement speeds in PD. Therefore, the aim of this study was to investigate tVNS effects on weight-shifting performance, anxiety, and related cortical activities at different shifting speeds in people with PD. Methods: The study recruited 15 PD patients with anxiety and 15 PD patients without anxiety. Each participant performed weight-shifting tasks on a force plate at different speed (slow: 0.25 Hz, medium: 0.33 Hz, fast: 0.50 Hz) with receiving active tVNS or sham tVNS. During the weight-shifting tasks, skin conductance signals and electroencephalogram (EEG) signals were also recorded. The primary outcomes included weight-shifting tracking error, weight-shifting trajectory jerk, weight-shifting amplitude, relative power of EEG, and subjective and objective anxiety levels. Statistical analyses were conducted by 2×2 mixed ANOVA with Bonferroni correction for post-hoc tests, to examine the effects of tVNS and group in each parameter except subjective anxiety level. The subjective anxiety level was examined by nonparametric analysis. Results: In terms of behavioral performance, the anxiety group showed reduced weight-shifting tracking error and increased weight-shifting trajectory jerk in active tVNS session, regardless of weight-shifting speed. On the other hand, the weight-shifting amplitude decreased under the 0.33 Hz condition in the non-anxiety group. The anxiety group reported higher subjective anxiety levels than the non-anxiety group under both 0.25 Hz and 0.33 Hz conditions. Regardless of the speed of weight-shifting, the anxiety group exhibited greater theta and alpha power at prefrontal, frontal, sensorimotor, and parietal-occipital cortices compared to the non-anxiety group. In contrast, the non-anxiety group exhibited greater high gamma power at sensorimotor area than the anxiety group. tVNS related EEG modulation was observed in slower speeds (0.25 Hz and 0.33 Hz) conditions. tVNS led to increased delta power and decreased high gamma power at prefrontal cortex in the non-anxiety group. In addition, tVNS resulted in decreased low gamma power at frontal cortex in the anxiety group. Conclusion: Brief tVNS could improve weight-shifting performance in anxiety PD group, and modulated brain activity particularly in the conditions with slower shifting speed. tVNS could be used as an adjunct intervention for improving weight-shifting performance for people with PD in the clinic. However, the tVNS effect on anxiety reduction was not observed in the present study. Further studies are needed with long-term tVNS intervention to confirm the benefits of tVNS to balance control, anxiety regulation, and brain activity in people with PD.