Giannini Marcello, Alexander David M, Nikolaev Andrey R, van Leeuwen Cees
Laboratory for Perceptual Dynamics, Brain & Cognition Research Unit, KU Leuven - University of Leuven, Tiensestraat 102, Box 3711, 3000, Leuven, Belgium.
Brain Topogr. 2018 Jul;31(4):608-622. doi: 10.1007/s10548-018-0622-2. Epub 2018 Jan 25.
In spontaneous, stimulus-evoked, and eye-movement evoked EEG, the oscillatory signal shows large scale, dynamically organized patterns of phase. We investigated eye-movement evoked patterns in free-viewing conditions. Participants viewed photographs of natural scenes in anticipation of a memory test. From 200 ms intervals following saccades, we estimated the EEG phase gradient over the entire scalp, and the wave activity, i.e. the goodness of fit of a wave model involving a phase gradient assumed to be smooth over the scalp. In frequencies centered at 6.5 Hz, large-scale phase organization occurred, peaking around 70 ms after fixation onset and taking the form of a traveling wave. According to the wave gradient, most of the times the wave spreads from the posterior-inferior to anterior-superior direction. In these directions, the gradients depended on the size and direction of the saccade. Wave propagation velocity decreased in the course of the fixation, particularly in the interval from 50 to 150 ms after fixation onset. This interval corresponds to the fixation-related lambda activity, which reflects early perceptual processes following fixation onset. We conclude that lambda activity has a prominent traveling wave component. This component consists of a short-term whole-head phase pattern of specific direction and velocity, which may reflect feedforward propagation of visual information at fixation.
在自发、刺激诱发和眼动诱发的脑电图中,振荡信号呈现出大规模、动态组织的相位模式。我们研究了自由观看条件下的眼动诱发模式。参与者在预期进行记忆测试的情况下观看自然场景照片。从扫视后200毫秒的时间间隔开始,我们估计了整个头皮上的脑电图相位梯度以及波活动,即涉及假设在头皮上平滑的相位梯度的波模型的拟合优度。在以6.5赫兹为中心的频率下,出现了大规模的相位组织,在注视开始后约70毫秒达到峰值,并呈现出行波的形式。根据波梯度,大多数情况下波从后下向前上方向传播。在这些方向上,梯度取决于扫视的大小和方向。波传播速度在注视过程中降低,特别是在注视开始后50至150毫秒的时间间隔内。这个时间间隔对应于与注视相关的λ活动,它反映了注视开始后的早期感知过程。我们得出结论,λ活动有一个突出的行波成分。这个成分由具有特定方向和速度的短期全脑相位模式组成,可能反映了注视时视觉信息的前馈传播。