Başar E, Rahn E, Demiralp T, Schürmann M
Institute of Physiology, Medical University Lübeck, Germany.
Electroencephalogr Clin Neurophysiol. 1998 Mar;108(2):101-9. doi: 10.1016/s0168-5597(97)00039-7.
Frontal visual evoked potentials (VEPs) were studied in order to extend the application of a recently introduced algorithm for selective averaging of evoked potentials. This algorithm is based on the inverse relationship between amplitudes of alpha or theta components of the spontaneous EEG activity and evoked potential (EP) amplitudes. Stimuli were only applied if the root mean square (RMS) value of the ongoing EEG at the lead F4 was below an individual threshold level ('selective stimulation'). For this comparison, the EEG was filtered in one of the frequency ranges 'alpha', 'theta' and 'alpha and theta', respectively. 'Alpha' and 'alpha-and-theta-dependent' selective stimulation conditions resulted in significant amplitude increases (P < 0.05) at the input reference channel F4 and partly at ipsihemispherical temporal and parietal leads and at Cz. The largest increase of 35% at F4 (P < 0.01) was obtained with visual stimulation during low prestimulus theta activity. We conclude that spontaneous theta activity of the frontal cortex may be a factor influencing the amplitudes of frontal VEPs. A sophisticated analysis of frontal EPs, mainly in the framework of cognitive studies, should consider the theta activity prior to stimulation.
为了扩展最近引入的一种用于诱发电位选择性平均的算法的应用，对额部视觉诱发电位（VEP）进行了研究。该算法基于自发脑电图活动的α或θ成分的振幅与诱发电位（EP）振幅之间的反比关系。仅当导联F4处的持续脑电图的均方根（RMS）值低于个体阈值水平时才施加刺激（“选择性刺激”）。为了进行此比较，脑电图分别在“α”、“θ”和“α和θ”频率范围之一中进行滤波。“α”和“α和θ依赖”选择性刺激条件导致输入参考通道F4以及部分同侧半球颞叶和顶叶导联以及Cz处的振幅显著增加（P < 0.05）。在低刺激前θ活动期间进行视觉刺激时，F4处获得了最大35%的增加（P < 0.01）。我们得出结论，额叶皮质的自发θ活动可能是影响额部VEP振幅的一个因素。对额部EP的深入分析，主要在认知研究的框架内，应考虑刺激前的θ活动。
