Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; AMI Centre, Aalto NeuroImaging, Aalto University School of Science, Espoo, Finland.
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Brain Stimul. 2022 Mar-Apr;15(2):523-531. doi: 10.1016/j.brs.2022.01.016. Epub 2022 Feb 14.
Transcranial magnetic stimulation (TMS) is widely used in brain research and treatment of various brain dysfunctions. However, the optimal way to target stimulation and administer TMS therapies, for example, where and in which electric field direction the stimuli should be given, is yet to be determined.
To develop an automated closed-loop system for adjusting TMS parameters (in this work, the stimulus orientation) online based on TMS-evoked brain activity measured with electroencephalography (EEG).
We developed an automated closed-loop TMS-EEG set-up. In this set-up, the stimulus parameters are electronically adjusted with multi-locus TMS. As a proof of concept, we developed an algorithm that automatically optimizes the stimulation orientation based on single-trial EEG responses. We applied the algorithm to determine the electric field orientation that maximizes the amplitude of the TMS-EEG responses. The validation of the algorithm was performed with six healthy volunteers, repeating the search twenty times for each subject.
The validation demonstrated that the closed-loop control worked as desired despite the large variation in the single-trial EEG responses. We were often able to get close to the orientation that maximizes the EEG amplitude with only a few tens of pulses.
Optimizing stimulation with EEG feedback in a closed-loop manner is feasible and enables effective coupling to brain activity.
经颅磁刺激（TMS）广泛应用于大脑研究和各种脑功能障碍的治疗。然而，刺激的最佳靶向和 TMS 治疗的最佳方式，例如刺激应该给予的位置和电场方向，仍有待确定。
开发一种基于脑电图（EEG）测量的 TMS 诱发脑活动的自动闭环系统，在线调整 TMS 参数（在这项工作中，是刺激方向）。
我们开发了一种自动闭环 TMS-EEG 设置。在该设置中，通过多部位 TMS 电子调整刺激参数。作为概念验证，我们开发了一种自动优化刺激方向的算法，该算法基于单次 EEG 响应。我们应用该算法确定最大程度地提高 TMS-EEG 响应幅度的电场方向。该算法的验证是在六名健康志愿者中进行的，每个受试者重复搜索二十次。
验证表明，尽管单次 EEG 响应存在很大差异，但闭环控制按预期工作。我们通常可以用几十次脉冲就能接近最大限度地提高 EEG 幅度的方向。
通过闭环方式使用 EEG 反馈进行刺激优化是可行的，并且能够有效地与大脑活动耦合。
