Granö Ida, Mutanen Tuomas P, Tervo Aino, Nieminen Jaakko O, Souza Victor H, Fecchio Matteo, Rosanova Mario, Lioumis Pantelis, Ilmoniemi Risto J
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.
Open Res Eur. 2022 Jul 11;2:45. doi: 10.12688/openreseurope.14634.2. eCollection 2022.
Spontaneous cortical oscillations have been shown to modulate cortical responses to transcranial magnetic stimulation (TMS). However, whether these oscillations influence cortical effective connectivity is largely unknown. We conducted a pilot study to set the basis for addressing how spontaneous oscillations affect cortical effective connectivity measured through TMS-evoked potentials (TEPs). We applied TMS to the left primary motor cortex and right pre-supplementary motor area of three subjects while recording EEG. We classified trials off-line into positive- and negative-phase classes according to the mu and beta rhythms. We calculated differences in the global mean-field amplitude (GMFA) and compared the cortical spreading of the TMS-evoked activity between the two classes. Phase affected the GMFA in four out of 12 datasets (3 subjects × 2 stimulation sites × 2 frequency bands). Two of the observed significant intervals were before 50 ms, two between 50 and 100 ms, and one after 100 ms post-stimulus. Source estimates showed complex spatial differences between the classes in the cortical spreading of the TMS-evoked activity. TMS-evoked effective connectivity seems to depend on the phase of local cortical oscillations at the stimulated site. This work paves the way to design future closed-loop stimulation paradigms.
自发皮层振荡已被证明可调节皮层对经颅磁刺激（TMS）的反应。然而，这些振荡是否影响皮层有效连接性在很大程度上尚不清楚。我们进行了一项初步研究，为解决自发振荡如何影响通过TMS诱发电位（TEP）测量的皮层有效连接性奠定基础。我们在记录脑电图的同时，对三名受试者的左侧初级运动皮层和右侧辅助运动区应用TMS。我们根据μ和β节律将离线试验分为正相和负相类别。我们计算了全局平均场振幅（GMFA）的差异，并比较了两类之间TMS诱发活动的皮层扩散。相位在12个数据集中的4个（3名受试者×2个刺激部位×2个频段）影响了GMFA。观察到的两个显著间隔在刺激后50毫秒之前，两个在50到100毫秒之间，一个在100毫秒之后。源估计显示，两类在TMS诱发活动的皮层扩散方面存在复杂的空间差异。TMS诱发的有效连接性似乎取决于受刺激部位局部皮层振荡的相位。这项工作为设计未来的闭环刺激范式铺平了道路。
