Clinical Neuroengineering, Neuro-X Institute, Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland; Clinical Neuroengineering, Neuro-X Institute, Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), EPFL Valais, Clinique Romande de Réadaptation, Sion, Switzerland.
Clinical Neuroengineering, Neuro-X Institute, Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland; Clinical Neuroengineering, Neuro-X Institute, Center for Neuroprosthetics (CNP) and Brain Mind Institute (BMI), EPFL Valais, Clinique Romande de Réadaptation, Sion, Switzerland; Department of Neurology, University Hospital Würzburg, Würzburg, Germany.
Brain Stimul. 2022 Jul-Aug;15(4):968-979. doi: 10.1016/j.brs.2022.06.012. Epub 2022 Jul 2.
Healthy older adults show a decrease in motor performance and motor learning capacity as well as in working memory (WM) performance. WM has been suggested to be involved in motor learning processes, such as sequence learning. Correlational evidence has shown the involvement of the frontoparietal network (FPN), a network underlying WM processes, in motor sequence learning. However, causal evidence is currently lacking. Non-invasive brain stimulation (NIBS) studies have focused so far predominantly on motor-related areas to enhance motor sequence learning while areas associated with more cognitive aspects of motor learning have not yet been addressed.
In this study, we aim to provide causal evidence for the involvement of WM processes and the underlying FPN in the successful performance of a motor sequence learning task by using theta transcranial alternating current stimulation (tACS) targeting the FPN during a motor sequence learning task.
In a cohort of 20 healthy older adults, we applied bifocal tACS in the theta range to the FPN during a sequence learning task. With the use of a double-blind, cross-over design, we tested the efficacy of active compared to sham stimulation. Two versions of the motor task were used: one with high and one with low WM load, to explore the efficacy of stimulation on tasks differing in WM demand. Additionally, the effects of stimulation on WM performance were addressed using an N-back task. The tACS frequency was personalized by means of EEG measuring the individual theta peak frequency during the N-back task.
The application of personalized theta tACS to the FPN improved performance during the motor sequence learning task with high WM load (p < .001), but not with low WM load. Active stimulation significantly improved both speed (p < .001), and accuracy (p = .03) during the task with high WM load. In addition, the stimulation paradigm improved performance on the N-back task for the 2-back task (p = .013), but not for 1-back and 3-back.
The performance during a motor sequence learning task can be enhanced by means of personalized bifocal theta tACS to the FPN when WM load is high, indicating that the efficacy of this stimulation paradigm is dependent on the cognitive demand during the learning task. These data provide further causal evidence for the critical involvement of WM processes and the FPN during the execution of a motor sequence learning task in healthy older. These findings open new exciting possibilities to counteract the age-related decline in motor performance, learning capacity and WM performance.
健康的老年人表现出运动表现和运动学习能力以及工作记忆（WM）表现下降。WM 被认为参与运动学习过程，例如序列学习。相关证据表明，与 WM 过程相关的额顶网络（FPN）参与了运动序列学习。然而，目前缺乏因果证据。非侵入性脑刺激（NIBS）研究迄今为止主要集中在与运动相关的区域，以增强运动序列学习，而与运动学习的更多认知方面相关的区域尚未得到解决。
在这项研究中，我们旨在通过在运动序列学习任务期间对 FPN 施加靶向 FPN 的 theta 经颅交流电刺激（tACS），为 WM 过程和基础 FPN 在成功执行运动序列学习任务中的参与提供因果证据。
在 20 名健康老年人的队列中，我们在序列学习任务期间在 theta 范围内对 FPN 施加双焦点 tACS。使用双盲、交叉设计，我们测试了与假刺激相比，主动刺激的效果。使用两种版本的运动任务：一种具有高 WM 负载，另一种具有低 WM 负载，以探索刺激对具有不同 WM 需求的任务的效果。此外，使用 N-back 任务来解决刺激对 WM 性能的影响。通过 EEG 测量 N-back 任务期间个体 theta 峰频率来个性化 tACS 频率。
将个性化 theta tACS 应用于 FPN 可改善高 WM 负载下的运动序列学习任务表现（p < 0.001），但低 WM 负载下则不然。主动刺激可显著提高高 WM 负载任务的速度（p < 0.001）和准确性（p = 0.03）。此外，刺激方案可提高 N-back 任务中 2-back 任务的表现（p = 0.013），但不能提高 1-back 和 3-back 任务的表现。
当 WM 负载较高时，通过对 FPN 进行个性化双焦点 theta tACS，可以增强运动序列学习任务的表现，这表明这种刺激方案的效果取决于学习任务期间的认知需求。这些数据为 WM 过程和 FPN 在健康老年人执行运动序列学习任务中的关键参与提供了进一步的因果证据。这些发现为对抗与年龄相关的运动表现、学习能力和 WM 表现下降开辟了新的令人兴奋的可能性。
