Mazaheri Ali, Jensen Ole
F. C. Donders Centre for Cognitive Neuroimaging, P.O. Box 9101, NL-6500 HB Nijmegen, The Netherlands.
Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2948-52. doi: 10.1073/pnas.0505785103. Epub 2006 Feb 10.
There is currently a debate as to whether event-related potentials and fields measured by using electroencephalography or magnetoencephalography are generated by ongoing oscillatory activity becoming phase-reset in response to a given stimulus. We performed a magnetoencephalography study measuring brain activity in response to visual stimuli. Using a measure termed the phase-preservation index we investigated the phase of oscillatory alpha activity (8-13 Hz) before and after the stimulus. We found that in single trials the alpha oscillations after visual stimuli preserve their phase relationship with respect to the phase before the stimuli. This finding argues against phase-resetting of ongoing oscillations as being responsible for visually evoked responses. The event-related field can be explained primarily by stimulus-locked activity in the band that is absent before the stimulus. These findings suggest that different neuronal events are responsible for generating the ongoing oscillations and the visually evoked responses.
目前存在一场争论，即通过脑电图或脑磁图测量的事件相关电位和场是否由持续的振荡活动在响应给定刺激时发生相位重置所产生。我们进行了一项脑磁图研究，测量对视觉刺激的脑活动。使用一种称为相位保持指数的测量方法，我们研究了刺激前后振荡性阿尔法活动（8 - 13赫兹）的相位。我们发现，在单次试验中，视觉刺激后的阿尔法振荡相对于刺激前的相位保持其相位关系。这一发现反对将持续振荡的相位重置视为视觉诱发反应的原因。事件相关场主要可以由刺激前不存在的频段中与刺激锁定的活动来解释。这些发现表明，不同的神经元事件负责产生持续振荡和视觉诱发反应。
