基于脑网络的多焦点经颅直流电刺激降低健康成年人双任务步态变异性的研究

关键词：脑网络  多焦点经颅直流电刺激  健康成年人  步态变异性

Keywords:brain network  multifocal transcranial direct current stimulation  healthy adults  gait variability

摘要：

      摘要 目的：步态表现与额顶网络（FPN）及默认网络（DN）的活动密切相关。本研究旨在探究靶向性调控FPN和DN的多焦点经颅直流电刺激（multifocal-tDCS）对健康成年人双任务步态表现的影响。 方法：选取40例健康成年人，随机分成多焦点tDCS组（20.70±2.45岁）和Sham组（21.55±2.03岁），每组20例。多焦点tDCS将8个电极放置于FPN和DN的关键大脑皮质，兴奋FPN同时抑制DN，总刺激强度小于4mA，时间为20min。Sham使用与多焦点tDCS相同的刺激时间、电流强度和电流加速过程，前30s内将电流升至2mA，然后在后30s内立即降至0（Sham仅提供了1min电流输入）。在电刺激前和刺激后即刻进行常速、快速和双任务步态测试，采集步态的基本时空参数（步幅、步速、步宽、步幅时间）和步态变异性指标，并据此计算双任务消耗（dual-task costs，即双任务表现相对于单任务表现的多余消耗）。采用重复测量双因素（刺激方案×刺激前后）方差分析评估多焦点tDCS对步态各项指标的影响。 结果：所有受试者均完成了本次试验，少数受试者在刺激后报告了轻微针刺感和皮肤发痒，无严重不良事件的报告。推测刺激类型总体正确率为48.00%，盲效良好。方差分析发现，双任务步态条件下的步宽变异性具有显著的时间和组别交互作用（P＜0.05）。具体而言，双任务步态条件下，多焦点tDCS组干预后步宽时间变异性下降了12.32%，Sham组干预后步宽时间变异性上升了22.57%。其他步态参数未观察到显著的交互作用。 结论：基于脑网络的多焦点tDCS对健康成年人的复杂步态控制能力具有一定调控作用，特别是双任务条件下的步态变异性。未来可以考虑将刺激方案应用到老年人，尤其是步态或认知障碍老年人群，以期更有效地帮助老年人提高复杂步态控制能力，降低跌倒风险。

Abstract:

      Abstract Objective： Gait performance is closely related to the activity of the frontoparietal network （FPN） and the default network （DN）. Therefore， the aim of this study was to investigate the effects of multifocal transcranial direct current stimulation （Multifocal-tDCS）， which targets the modulation of FPN and DN， on dual-task gait performance in healthy adults. Method： Forty healthy adults were selected and randomly divided into the Multifocal tDCS group （20.70±2.45 years） and the Sham group （21.55±2.03 years）， with 20 participants in each group. The Multifocal tDCS placed eight electrodes in the critical cerebral cortex of the FPN and DN， exciting the FPN while inhibiting the DN， with a total stimulation intensity of less than 4mA for 20min. The Sham was given the same stimulation time， current intensity and current acceleration procedure as the Multifocal tDCS， ramping up the current to 2mA in the first 30s and then immediately dropping to 0 in the second 30s （i.e.， only 1min of current was delivered in the Sham）. Normal， fast and dual-task gait tests were performed before and immediately after receiving a tDCS， and basic spatio-temporal parameters of gait （i.e.， gait stride length， gait speed， gait step width， and gait stride time）， gait variability indicators， and Dual-task costs （i.e. the excess consumption of dual-task performance relative to single-task performance） were collected. The effect of Multifocal tDCS on gait metrics was examined by two-way repeated measures ANOVA. Result： All subjects completed this experiment， with a few subjects reporting a mild pins and needles sensation and itchy skin after stimulation. No serious adverse events were reported. The overall correct rate of guessing the type of stimulation was 48.00 %， with a good blind effect. ANOVA revealed a significant time and group interaction for gait step width variability in the dual-task gait condition （P<0.05）. Specifically， in the dual-task gait condition， gait step width variability decreased by 12.32% in the Multifocal tDCS group and increased by 22.57% in the Sham group after the intervention. No significant interactions were observed for any of the other gait parameters. Conclusion： Brain network-based Multifocal tDCS can effectively modulate the ability to modulate complex gait control in healthy adults， particularly gait variability in dual-task conditions. The application of this new technique to older adults， especially those with gait and cognitive impairments， could be considered in the future， with the aim of more effectively helping older adults to improve complex gait control and reduce the risk of falls.