Barry Robert J, Rushby Jacqueline A, Johnstone Stuart J, Clarke Adam R, Croft Rodney J, Lawrence Carlie A
Brain & Behaviour Research Institute and Department of Psychology, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
Clin Neurophysiol. 2004 Nov;115(11):2593-601. doi: 10.1016/j.clinph.2004.06.004.
We aimed to examine the relation between the phase of electroencephalogram (EEG) alpha activity at stimulus onset and event-related potentials (ERPs) in a fixed-inter-stimulus interval auditory 'oddball' task, using a novel conceptualisation of orthogonal phase effects (cortical negativity versus positivity, negative driving versus positive driving, waxing versus waning).
EEG responses to button-press targets, from 14 subjects presented with 4 blocks of 150 stimuli (50% target probability), were examined. Pre-stimulus alpha activity (8-13 Hz) at Pz was assessed for each trial by digital filtering of the EEG. The alpha cycle at Pz, starting from a negative-going zero crossing, was used to sort trials into 4 phases, for which ERPs were derived from both the filtered and unfiltered EEG activity at Fz, Cz, and Pz.
Preferred brain states in this paradigm were indicated by an 8% greater occurrence of negative driving than positive driving, and a 33% greater occurrence of waxing than waning phases. Negative driving phases were associated with increased N1 latencies and decreased N2 amplitudes. Latencies of N1 and P2 were reduced in waxing phases. These reflected systematic changes in alpha frequency and amplitude at stimulus onset.
In a fixed-inter-stimulus interval paradigm, component frequencies of the EEG are dynamically adjusted in order to provide brain states at the moment of stimulus presentation which differentially affect the EEG correlates of stimulus processing.
The results add to our understanding of the genesis of the ERP, indicating the importance of the dynamic interplay between instantaneous EEG activity and stimulus processing reflected in the ERP.
我们旨在通过对正交相位效应（皮质负性与正性、负向驱动与正向驱动、增强与减弱）的一种新颖概念化，研究在固定刺激间隔听觉“oddball”任务中刺激开始时脑电图（EEG）α活动的相位与事件相关电位（ERP）之间的关系。
研究了14名受试者对按键目标的EEG反应，这些受试者接受了4个包含150个刺激（目标概率为50%）的组块。通过对EEG进行数字滤波，评估每次试验在Pz处的刺激前α活动（8 - 13 Hz）。从负向过零点开始的Pz处的α周期用于将试验分为4个相位，对于这些相位，ERP是从Fz、Cz和Pz处的滤波和未滤波EEG活动中得出的。
该范式中偏好的脑状态表现为负向驱动比正向驱动出现的频率高8%，增强比减弱阶段出现的频率高33%。负向驱动阶段与N1潜伏期增加和N2波幅降低相关。N1和P2的潜伏期在增强阶段缩短。这些反映了刺激开始时α频率和波幅的系统性变化。
在固定刺激间隔范式中，EEG的成分频率会动态调整，以便在刺激呈现时刻提供不同影响刺激处理的EEG相关指标的脑状态。
这些结果增进了我们对ERP起源的理解，表明了瞬时EEG活动与ERP中反映的刺激处理之间动态相互作用的重要性。
