Başar Erol, Gölbaşı Bilge Turp
Brain Dynamics, Cognition and Complex Systems Research Center, Istanbul Kultur University, 34156 Istanbul, Turkey.
Cogn Neurodyn. 2014 Dec;8(6):437-45. doi: 10.1007/s11571-014-9301-5. Epub 2014 Aug 1.
The present research aims to show that the occurrence of alpha blocking or event-related desynchronization (ERD) strongly depends on the amplitude and also on the phase angle of alpha activity at the stimulus onset. Simple visual stimulation was presented to 17 healthy subjects during EEG recording. An O2 electrode was used for analysis with a 32 channel EEG sampling system. We used a segmentation of raw data in order to obtain the evoked potential. Prestimulus and poststimulus activities were filtered in the alpha (8-13 Hz) frequency band. Later, four different events (blocked, time-locked, phase-locked, and eliminated) were separately averaged. Phase-locked sweeps were determined by application of inter-trial coherence analysis. The evaluation of the data shows that "time-locked and phase-locked sweeps" were the dominating pattern and not "the blocked pattern", which occurred only when the prestimulus alpha was high. In the analyses of EEG-EP sweeps, only 22 % of epochs showed (ERD). The ANOVA revealed significant differences between four different alpha responses (F(3,48) = 11.175; p < 0.001). Furthermore, alpha oscillations in time-locked responses were significantly higher than blocked (p < 0.0001). The analyses clearly demonstrate that important precaution is needed when using the ERD as a cognitive or pathological marker.
本研究旨在表明，α阻断或事件相关去同步化（ERD）的出现强烈依赖于刺激开始时α活动的幅度以及相位角。在脑电图（EEG）记录期间，对17名健康受试者进行简单视觉刺激。使用O2电极通过32通道EEG采样系统进行分析。我们对原始数据进行分段以获得诱发电位。刺激前和刺激后的活动在α（8 - 13赫兹）频段进行滤波。随后，分别对四种不同事件（阻断、时间锁定、相位锁定和消除）进行平均。通过应用试次间相干分析确定相位锁定扫描。数据评估表明，“时间锁定和相位锁定扫描”是主导模式，而非“阻断模式”，后者仅在刺激前α值较高时出现。在EEG - EP扫描分析中，只有22%的时段显示出（ERD）。方差分析显示四种不同α反应之间存在显著差异（F(3,48) = 11.175；p < 0.001）。此外，时间锁定反应中的α振荡明显高于阻断反应（p < 0.0001）。分析清楚地表明，在将ERD用作认知或病理标志物时需要采取重要的预防措施。
