Fuentemilla Ll, Marco-Pallarés J, Grau C
Neurodynamics Laboratory, Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Passeig de la Vall d'Hebron 171, 08035 Barcelona, Catalonia, Spain.
Neuroimage. 2006 Apr 15;30(3):909-16. doi: 10.1016/j.neuroimage.2005.10.036. Epub 2006 Jan 11.
Nowadays, the mechanisms involved in the genesis of event-related potentials (ERPs) are a matter of debate among neuroscientists. Specifically, the debate lies in whether ERPs arise due to the contribution of a fixed-polarity and fixed-latency superimposed neuronal activity to background electroencephalographic oscillations (evoked model) and/or due to a partial phase synchronization of the ongoing EEG (oscillatory model). The participation of the two mechanisms can be explored by the spectral power modulation and phase coherence of scalp EEG rhythms, respectively. However, an important limitation underlies their measurement: the fact that an added neural activity will be relatively phase-locked to stimulus, thus enhancing both spectral power and phase synchrony measures and making the contribution of each mechanism less clear-cut. This would not be relevant in the case that an increase in phase concentration was not accompanied by any concurrent spectral power modulation, thus opening the way to an oscillatory-based explanation. We computed event-related spectral power modulations and phase coherence to an auditory repeated-stimulus presentation paradigm with tone intensity far from threshold (90 dB SPL), in which N1 decreases its amplitude (N1 gating) as an attenuation brain process. Our data indicate that evoked and oscillatory activity could contribute together to the non-attenuated N1, while N1 to repeated stimuli could be explained by partial phase concentration of scalp EEG activity without concurrent power increase. Therefore, our results show that both increased spectral power and partial phase resetting contribute differentially to different ERPs. Moreover, they show that certain ERPs could arise through reorganization of the phase of ongoing scalp EEG activity only.
如今，事件相关电位（ERP）产生的机制是神经科学家们争论的焦点。具体而言，争论在于ERP的产生是由于具有固定极性和固定潜伏期的叠加神经元活动对背景脑电图振荡的贡献（诱发模型）和/或由于持续脑电图的部分相位同步（振荡模型）。这两种机制的参与情况可分别通过头皮脑电图节律的频谱功率调制和相位相干性来探究。然而，它们的测量存在一个重要局限性：即额外的神经活动会相对与刺激锁相，从而增强频谱功率和相位同步测量，使得每种机制的贡献变得不那么明确。如果相位集中增加而没有任何同时发生的频谱功率调制，这种情况就不相关，从而为基于振荡的解释开辟了道路。我们计算了对音调强度远高于阈值（90 dB SPL）的听觉重复刺激呈现范式的事件相关频谱功率调制和相位相干性，其中N1作为一种衰减的脑过程，其振幅会降低（N1门控）。我们的数据表明，诱发活动和振荡活动可能共同促成未衰减的N1，而对重复刺激的N1可以通过头皮脑电图活动的部分相位集中来解释，而没有同时的功率增加。因此，我们的结果表明，频谱功率增加和部分相位重置对不同的ERP有不同的贡献。此外，它们表明某些ERP可能仅通过正在进行的头皮脑电图活动相位的重组而产生。
