IRCCS San Camillo Hospital, Venice, Italy.
Human Inspired Technologies Research Center, University of Padova, Padua, Italy.
Sci Rep. 2021 Apr 7;11(1):7659. doi: 10.1038/s41598-021-87371-z.
High-definition transcranial direct current stimulation (HD-tDCS) seems to overcome a drawback of traditional bipolar tDCS: the wide-spread diffusion of the electric field. Nevertheless, most of the differences that characterise the two techniques are based on mathematical simulations and not on real, behavioural and neurophysiological, data. The study aims to compare a widespread tDCS montage (i.e., a Conventional bipolar montage with extracephalic return electrode) and HD-tDCS, investigating differences both at a behavioural level, in terms of dexterity performance, and a neurophysiological level, as modifications of alpha and beta power as measured with EEG. Thirty participants took part in three sessions, one for each montage: Conventional tDCS, HD-tDCS, and sham. In all the conditions, the anode was placed over C4, while the cathode/s placed according to the montage. At baseline, during, and after each stimulation condition, dexterity was assessed with a Finger Tapping Task. In addition, resting-state EEG was recorded at baseline and after the stimulation. Power spectrum density was calculated, selecting two frequency bands: alpha (8-12 Hz) and beta (18-22 Hz). Linear mixed effect models (LMMs) were used to analyse the modulation induced by tDCS. To evaluate differences among the montages and consider state-dependency phenomenon, the post-stimulation measurements were covariate-adjusted for baseline levels. We observed that HD-tDCS induced an alpha power reduction in participants with lower alpha at baseline. Conversely, Conventional tDCS induced a beta power reduction in participants with higher beta at baseline. Furthermore, data showed a trend towards a behavioural effect of HD-tDCS in participants with lower beta at baseline showing faster response times. Conventional and HD-tDCS distinctively modulated cortical activity. The study highlights the importance of considering state-dependency to determine the effects of tDCS on individuals.
高清晰度经颅直流电刺激（HD-tDCS）似乎克服了传统双极 tDCS 的一个缺点：电场的广泛扩散。然而，这两种技术的大多数区别都是基于数学模拟，而不是基于真实的、行为和神经生理学数据。本研究旨在比较一种广泛使用的 tDCS 导联（即带有额外颅外返回电极的传统双极导联）和 HD-tDCS，从行为水平（灵巧性能）和神经生理学水平（脑电图测量的 alpha 和 beta 功率的变化）两个方面研究两者之间的差异。30 名参与者参加了三个会话，每个会话一个：传统 tDCS、HD-tDCS 和假刺激。在所有条件下，阳极置于 C4 上方，阴极根据导联放置。在基线、刺激期间和刺激后，使用手指敲击任务评估灵巧性。此外，在基线和刺激后记录静息状态 EEG。计算功率谱密度，选择两个频带：alpha（8-12 Hz）和 beta（18-22 Hz）。使用线性混合效应模型（LMMs）分析 tDCS 引起的调制。为了评估导联之间的差异并考虑状态依赖性现象，将刺激后的测量值针对基线水平进行协变量调整。我们观察到，HD-tDCS 降低了基线时 alpha 功率较低的参与者的 alpha 功率。相反，传统 tDCS 降低了基线时 beta 功率较高的参与者的 beta 功率。此外，数据显示，基线时 beta 较低的参与者的 HD-tDCS 具有行为效应的趋势，表现为反应时间更快。传统和 HD-tDCS 以不同的方式调节皮质活动。该研究强调了考虑状态依赖性来确定 tDCS 对个体影响的重要性。
