Kayser Jürgen, Tenke Craig E
Department of Biopsychology, New York State Psychiatric Institute, New York, NY 10032, USA.
Clin Neurophysiol. 2006 Feb;117(2):348-68. doi: 10.1016/j.clinph.2005.08.034. Epub 2005 Dec 13.
To evaluate the effectiveness and comparability of PCA-based simplifications of ERP waveforms versus their reference-free Laplacian transformations for separating task- and response-related ERP generator patterns during auditory oddball tasks.
Nose-referenced ERPs (31 sites total) were recorded from 66 right-handed adults during oddball tasks using syllables or tones. Response mode (left press, right press, silent count) and task was varied within subjects. Spherical spline current source density (CSD) waveforms were computed to sharpen ERP scalp topographies and eliminate volume-conducted contributions. ERP and CSD data were submitted to separate covariance-based, unrestricted temporal PCAs (Varimax) to disentangle temporally and spatially overlapping ERP and CSD components.
Corresponding ERP and CSD factors were unambiguously related to known ERP components. For example, the dipolar organization of a central N1 was evident from factorized anterior sinks and posterior sources encompassing the Sylvian fissure. Factors associated with N2 were characterized by asymmetric frontolateral (tonal: frontotemporal R > L) and parietotemporal (phonetic: parietotemporal L > R) sinks for targets. A single ERP factor summarized parietal P3 activity, along with an anterior negativity. In contrast, two CSD factors peaking at 360 and 560 ms distinguished a parietal P3 source with an anterior sink from a centroparietal P3 source with a sharply localized Fz sink. A smaller parietal but larger left temporal P3 source was found for silent count compared to button press. Left or right press produced opposite, region-specific asymmetries originating from central sites, modulating the N2/P3 complex.
CSD transformation is shown to be a valuable preprocessing step for PCA of ERP data, providing a unique, physiologically meaningful solution to the ubiquitous reference problem. By reducing ERP redundancy and producing sharper, simpler topographies, and without losing or distorting any effects of interest, the CSD-PCA solution replicated and extended previous task- and response-related findings.
Eliminating ambiguities of the recording reference, the combined CSD-PCA approach systematically bridges between montage-dependent scalp potentials and distinct, anatomically-relevant current generators, and shows promise as a comprehensive, generic strategy for ERP analysis.
评估基于主成分分析（PCA）的事件相关电位（ERP）波形简化方法与无参考拉普拉斯变换方法在听觉oddball任务中分离任务相关和反应相关ERP发生器模式的有效性和可比性。
在oddball任务中，使用音节或音调记录了66名右利手成年人的鼻参考ERP（共31个位点）。反应模式（左按、右按、默读计数）和任务在受试者内变化。计算球面样条电流源密度（CSD）波形以锐化ERP头皮地形图并消除容积传导贡献。ERP和CSD数据分别提交给基于协方差的无限制时间PCA（Varimax），以解开时间和空间上重叠的ERP和CSD成分。
相应的ERP和CSD因子与已知的ERP成分明确相关。例如，中央N1的偶极组织从包括外侧裂的分解前向汇和后向源中明显可见。与N2相关的因子的特征是目标的不对称额外侧（音调：额颞部右>左）和顶颞部（语音：顶颞部左>右）汇。一个单一ERP因子总结了顶叶P3活动以及一个前负波。相比之下，在360和560毫秒达到峰值的两个CSD因子区分了一个具有前向汇的顶叶P3源和一个具有尖锐定位的Fz汇的中央顶叶P3源。与按键相比，默读计数时发现顶叶P3源较小但左侧颞叶P3源较大。左按或右按产生相反的、源自中央位点的区域特异性不对称性，调节N2/P3复合体。
CSD变换被证明是ERP数据PCA的一个有价值的预处理步骤，为普遍存在的参考问题提供了一个独特的、具有生理意义的解决方案。通过减少ERP冗余并产生更清晰、更简单的地形图，且不丢失或扭曲任何感兴趣的效应，CSD-PCA解决方案复制并扩展了先前与任务和反应相关的发现。
消除记录参考的模糊性，联合CSD-PCA方法系统地架起了蒙太奇依赖头皮电位与不同的、解剖学相关电流发生器之间的桥梁，并显示出作为ERP分析的一种全面、通用策略的前景。
