Department of Neurology, University Hospital, LMU Munich, Munich, Germany.
German Center for Vertigo and Balance Disorders, University Hospital, LMU Munich, Munich, Germany.
Eur J Neurosci. 2020 Apr;51(7):1657-1675. doi: 10.1111/ejn.14543. Epub 2019 Aug 28.
Self-motion perception is a key aspect of higher vestibular processing, suggested to rely upon hemispheric lateralization and alpha-band oscillations. The first aim of this study was to test for any lateralization in the EEG alpha band during the illusory sense of self-movement (vection) induced by large optic flow stimuli. Visual stimuli flickered at alpha frequency (approx. 10 Hz) in order to produce steady state visually evoked potentials (SSVEPs), a robust EEG measure which allows probing the frequency-specific response of the cortex. The first main result was that differential lateralization of the alpha SSVEP response was found during vection compared with a matched random motion control condition, supporting the idea of lateralization of visual-vestibular function. Additionally, this effect was frequency-specific, not evident with lower frequency SSVEPs. The second aim of this study was to test for a causal role of the right hemisphere in producing this lateralization effect and to explore the possibility of selectively modulating the SSVEP response. Transcranial alternating current stimulation (tACS) was applied over the right hemisphere simultaneously with SSVEP recording, using a novel artefact removal strategy for combined tACS-EEG. The second main result was that tACS enhanced SSVEP amplitudes, and the effect of tACS was not confined to the right hemisphere. Subsequent control experiments showed the effect of tACS requires the flicker frequency and tACS frequency to be closely matched and tACS to be of sufficient intensity. Combined tACS-SSVEPs are a promising method for future investigation into the role of neural oscillations and for optimizing tACS.
自我运动感知是高级前庭处理的一个关键方面，据推测它依赖于半球侧化和α 波段振荡。本研究的第一个目的是测试在由大光流刺激引起的虚幻自我运动（视动）期间，α 波段脑电图中是否存在任何侧化。视觉刺激以α 频率（约 10 Hz）闪烁，以产生稳态视觉诱发电位（SSVEP），这是一种强大的脑电图测量方法，可用于探测皮层的频率特异性反应。第一个主要结果是，与匹配的随机运动对照条件相比，在视动期间发现了 α SSVEP 反应的差异侧化，这支持了视觉-前庭功能侧化的想法。此外，这种效应是频率特异性的，低频 SSVEP 中并不明显。本研究的第二个目的是测试右半球在产生这种侧化效应中的因果作用，并探索选择性调节 SSVEP 反应的可能性。经颅交流电刺激（tACS）在 SSVEP 记录的同时应用于右半球，使用一种新的用于组合 tACS-EEG 的伪影去除策略。第二个主要结果是，tACS 增强了 SSVEP 幅度，并且 tACS 的效果不仅局限于右半球。随后的对照实验表明，tACS 的效果需要闪烁频率和 tACS 频率紧密匹配，并且 tACS 强度足够。组合 tACS-SSVEP 是未来研究神经振荡作用和优化 tACS 的有前途的方法。
