Mazaheri Ali, Picton Terence W
Rotman Research Institute, Baycrest Centre for Geriatric Care, 3560 Bathurst Street, Toronto, Canada M6A 2E1.
Brain Res Cogn Brain Res. 2005 Jun;24(1):81-96. doi: 10.1016/j.cogbrainres.2004.12.013. Epub 2005 Feb 19.
This study measured the changes in the spectrum of the EEG (electroencephalogram) and in the event-related potentials (ERPs) as subjects detected an improbable target in a train of standard stimuli. The intent was to determine how these measurements are related, and to what extent the ERPs might represent phase-locked changes in EEG rhythms. The experimental manipulations were the stimulus modality (auditory or visual), the discriminability of the target, and the presence or absence of distraction. The ERPs showed sensory-evoked potentials that were specific to the modality and a target-evoked P300 wave that was later in the visual modality than in the auditory, and later and smaller when the discrimination was more difficult. The averaged EEG spectrograms showed that targets increased the frontal theta activity, decreased posterior and central alpha and beta activity, and decreased the central gamma activity. The scalp topography of the changes in the alpha and beta activity indicated a posterior desynchronization specific for the visual task and occurring with both targets and standards and a more widespread desynchronization for targets in either modality. Increased phase synchronization occurred during the event-related potentials, but modeling demonstrated that this can be seen when an evoked potential waveform is simply added to the background EEG. However, subtracting the spectrogram of the average ERP from the average spectrogram of the single trials indicated that phase-resetting of the background EEG rhythms can occur during the ERP. The idea that the ERPs and the EEG rhythms "share generators" can explain these findings.
本研究测量了受试者在一系列标准刺激中检测到一个不太可能出现的目标时，脑电图（EEG）频谱和事件相关电位（ERP）的变化。目的是确定这些测量之间的关系，以及ERP在多大程度上可能代表EEG节律的锁相变化。实验操作包括刺激方式（听觉或视觉）、目标的可辨别性以及是否存在干扰。ERP显示出特定于刺激方式的感觉诱发电位，以及目标诱发的P300波，该波在视觉刺激方式中比在听觉刺激方式中出现得更晚，并且在辨别更困难时出现得更晚且幅度更小。平均EEG频谱图显示，目标增加了额叶θ活动，降低了后部和中央α及β活动，并降低了中央γ活动。α和β活动变化的头皮地形图表明，视觉任务特有的后部去同步化在目标和标准刺激时均会出现，并且在任何一种刺激方式下，目标引起的去同步化更为广泛。在事件相关电位期间出现了相位同步增加，但建模表明，当将诱发电位波形简单地添加到背景EEG中时也能观察到这种情况。然而，从单次试验的平均频谱图中减去平均ERP的频谱图表明，在ERP期间背景EEG节律可能会发生相位重置。ERP和EEG节律“共享发生器”这一观点可以解释这些发现。
