Demiralp T, Ademoglu A, Comerchero M, Polich J
Department of Physiology, Istanbul Medical Faculty, Istanbul University, Capa-Istanbul, Turkey.
Brain Topogr. 2001 Summer;13(4):251-67. doi: 10.1023/a:1011102628306.
Target/standard discrimination difficulty and the degree of stimulus "novelty" were manipulated systematically in a three-stimulus odd-ball task to assess how these variables affect target and non-target P300 scalp distributions for visual stimuli. Wavelet transformation (WT) analyses were performed on the non-target (P3a) and target (P3b) ERPs to assay how the underlying electroencephalographic (EEG) activity was affected by both the difficulty and novelty factors. When target/standard discrimination was easy, P300 amplitude was higher for the target than the non-target across all electrode sites, and both demonstrated parietal maximums. In contrast, when target/standard discrimination was difficult, non-target amplitude (P3a) was higher and earlier over the frontal/central electrode sites for both levels of novelty, whereas target amplitude (P3b) was greater parietally and occurred later than the non-target components and was generally unaffected by non-target novelty level. The WT analyses indicated that appreciable theta activity was related to the more novel non-target stimuli; primarily target component delta coefficients were affected by the discrimination difficulty variable. The findings suggest that target/standard discrimination difficulty, rather than stimulus novelty, determines P3a generation for visual stimuli but that the underlying theta oscillations are differentially affected by stimulus novelty. WT analysis methods are discussed along with the theoretical and neurophysiological implications of the findings.
在一项三刺激异常球任务中，系统地操纵了目标/标准辨别难度和刺激“新颖性”程度，以评估这些变量如何影响视觉刺激的目标和非目标P300头皮分布。对非目标（P3a）和目标（P3b）事件相关电位进行小波变换（WT）分析，以测定潜在的脑电图（EEG）活动如何受到难度和新颖性因素的影响。当目标/标准辨别容易时，在所有电极部位，目标的P300波幅高于非目标，且两者均在顶叶出现最大值。相反，当目标/标准辨别困难时，对于两种新颖性水平，在额叶/中央电极部位，非目标波幅（P3a）更高且出现更早，而目标波幅（P3b）在顶叶更大，且比非目标成分出现更晚，并且一般不受非目标新颖性水平的影响。WT分析表明，明显的θ活动与更新颖的非目标刺激有关；主要目标成分的δ系数受辨别难度变量的影响。研究结果表明，对于视觉刺激，目标/标准辨别难度而非刺激新颖性决定了P3a的产生，但潜在的θ振荡受刺激新颖性的影响不同。本文讨论了WT分析方法以及研究结果的理论和神经生理学意义。
