Department of Physical Therapy, Faculty of Health Sciences, Ariel University, Ariel, Israel.
Department of Physical Therapy, Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
J Neuroeng Rehabil. 2021 Jun 26;18(1):103. doi: 10.1186/s12984-021-00899-z.
The results of transcranial direct current stimulation (tDCS) studies that seek to improve motor performance for people with neurological disorders, by targeting the primary motor cortex, have been inconsistent. One possible reason, among others, for this inconsistency, is that very little is known about the optimal protocols for enhancing motor performance in healthy individuals. The best way to optimize stimulation protocols for enhancing tDCS effects on motor performance by means of current intensity modulation has not yet been determined. We aimed to determine the effect of current intensity on motor performance using-for the first time-a montage optimized for maximal focal stimulation via anodal high-definition tDCS (HD-tDCS) on the right primary motor cortex in healthy subjects.
Sixty participants randomly received 20-min HD-tDCS at 1.5, 2 mA, or sham stimulation. Participants' reaching performance with the left hand on a tablet was tested before, during, and immediately following stimulation, and retested after 24 h.
In the current montage of HD-tDCS, movement time did not differ between groups in each timepoint. However, only after HD-tDCS at 1.5 mA did movement time improve at posttest as compared to pretest. This reduction in movement time from pretest to posttest was significantly greater compared to HD-tDCS 2 mA. Following HD-tDCS at 1.5 mA and sham HD-tDCS, but not 2 mA, movement time improved at retest compared to pretest, and at posttest and retest compared to the movement time during stimulation. In HD-tDCS at 2 mA, the negligible reduction in movement time from the course of stimulation to posttest was significantly lower compared to sham HD-tDCS. Across all groups, reaction time improved in retest compared to pretest and to the reaction time during stimulation, and did not differ between groups in each timepoint.
It appears that 2 mA in this particular experimental setup inhibited the learning effects. These results suggest that excitatory effects induced by anodal stimulation do not hold for every stimulation intensity, information that should be taken into consideration when translating tDCS use from the realm of research into more optimal neurorehabilitation.
Clinical Trials Gov, NCT04577768. Registered 6 October 2019 -Retrospectively registered, https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S000A9B3&selectaction=Edit&uid=U0005AKF&ts=8&cx=buucf0 .
针对患有神经障碍的人群，通过靶向初级运动皮层来提高运动表现的经颅直流电刺激（tDCS）研究结果一直不一致。原因之一可能是，对于如何在健康个体中优化刺激方案以增强运动表现，我们知之甚少。通过电流强度调制来优化刺激方案以增强 tDCS 对运动表现的影响的最佳方法尚未确定。我们旨在通过首次在健康受试者的右初级运动皮层上使用经颅直流电刺激（HD-tDCS）优化的刺激模式来确定电流强度对运动表现的影响。
60 名参与者随机接受 20 分钟 1.5mA、2mA 或假刺激的 HD-tDCS。在刺激前、刺激期间和刺激后立即以及 24 小时后，参与者使用平板电脑测试左手的伸展表现。
在当前的 HD-tDCS 电流模式下，各组在每个时间点的运动时间均无差异。然而，只有在接受 1.5mA 的 HD-tDCS 后，与预测试相比，后测试中的运动时间才有所改善。与 2mA 的 HD-tDCS 相比，这种从预测试到后测试的运动时间的减少更为显著。在接受 1.5mA 的 HD-tDCS 和假 HD-tDCS 后，但不是 2mA 的 HD-tDCS 后，与预测试相比，在测试后和在测试后和在测试期间相比，运动时间有所改善。在 2mA 的 HD-tDCS 中，从刺激过程到后测试的运动时间的微小减少明显低于假 HD-tDCS。在所有组中，与预测试和刺激期间的反应时间相比，在测试后和测试后，反应时间都有所改善，并且在每个时间点各组之间均无差异。
在这种特定的实验设置中，2mA 似乎抑制了学习效果。这些结果表明，阳极刺激引起的兴奋作用并不适用于每个刺激强度，在将 tDCS 的使用从研究领域转化为更优化的神经康复领域时，应该考虑到这一点。
临床试验.gov，NCT04577768。2019 年 10 月 6 日注册-回顾性注册，https://register.clinicaltrials.gov/prs/app/action/SelectProtocol？sid=S000A9B3&selectaction=Edit&uid=U0005AKF&ts=8&cx=buucf0。
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