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Principal components analysis (PCA) can facilitate analysis of event-related potential (ERP) components. Geomin, Oblimin, Varimax, Promax, and Infomax (independent components analysis) were compared using a simulated data set. Kappa settings for Oblimin and Promax were also systematically compared. Finally, the rotations were also analyzed in a two-step PCA procedure, including a contrast between spatiotemporal and temporospatial procedures. Promax was found to give the best overall results for temporal PCA, and Infomax was found to give the best overall results for spatial PCA. The current practice of kappa values of 3 or 4 for Promax and 0 for Oblimin was supported. Source analysis was meaningfully improved by temporal Promax PCA over the conventional windowed difference wave approach (from a median 32.9 mm error to 6.7 mm). It was also found that temporospatial PCA produced modestly improved results over spatiotemporal PCA.

Consistent with the notion that emotional stimuli receive preferential attention and perceptual processing, many event-related potential (ERP) components appear sensitive to emotional stimuli. In an effort to differentiate components that are sensitive to emotional versus neutral stimuli, the current study utilized temporospatial principal components analysis to analyze ERPs from a large sample (N=82) while pleasant, neutral, and unpleasant images were passively viewed. Several factors sensitive to emotional stimuli were identified-corresponding to the N1, early posterior negativity (EPN), and P3; multiple factors resembling the late positive potential (LPP) emerged. Results indicate that the N1 represents the earliest component modulated by emotional stimuli; the EPN and the LPP represent unique components; the scalp-recorded LPP appears to include a P3-like positivity as well as additional positivities at occipital and central recording sites.

Falkenstein, Hohnsbein, and Hoorman (1994) suggested that common measures of P300 latency confound a "P-SR" component whose latency corresponds to stimulus evaluation time and a "P-CR" component whose latency varies with response-selection time, thus casting doubt on work in mental chronometry that relies on P300 latency. We report here a replication and extension of Falkenstein et al. (1994) using a high-density 129-electrode montage with 11 subjects. Spatiotemporal PCA was used to extract the components of the ERP. A centroid measure is also introduced for detecting waveform-timing changes beyond just peak latency. In terms of componentry, we argue that the P-SR and the P-CR, correspond to the P3a/Novelty P3 and the P300, respectively. Conceptually, we dispute the proposed distinction between stimulus evaluation and response selection. We suggest a four-stage ERP model of information processing and place the P3a and the P300 in this framework.

Distinct event-related potential effects have been related to familiarity and recollection processes underlying recognition memory. Familiarity has been conceptualized as similar either to perceptual priming mechanisms supporting implicit memory or to amodal global-matching processes that should show little sensitivity to perceptual variables. The present experiment manipulated the study modality of words (auditory, visual) that were visually tested for recognition memory. The mid-frontal (300-500 ms) old/new effect often attributed to familiarity was not affected by study modality, so it appears related to an amodal familiarity process. An earlier (176-260 ms) fronto-polar old/new effect was perceptually specific in that it was observed only following visual study. The parietal old/new effect (400-800 ms), often attributed to recollection, was similar following both visual and auditory study. Temporal-spatial PCA clarified the separability of these effects.

We used a novel application of principal components analysis (spatiotemporal PCA) to decompose the event-related brain potentials (ERPs) obtained with a dense electrode array, with the purpose of elucidating the late ERP components elicited by deviant stimuli under "attend" and "ignore" conditions. First, a "spatial" PCA was performed to identify a set of scalp distributions (spatial factors or "virtual electrodes") that accounted for the spatial variance in the data set. The data were expressed as spatial factor scores or "virtual ERPs" measured at each of the virtual electrodes. These virtual ERPs were submitted to a "temporal" PCA, yielding a set of temporal factors or "virtual epochs." Statistical analyses of the temporal factor scores found that (1) attended deviant stimuli elicited the P300 and Novelty P3 components, the latter being largest for highly salient nontargets: (2) "ignored" deviants elicited a small Novelty P3, and depending on the primary task, a small P300: and (3) the classical Slow Wave consisted of separate frontal-negative and posterior-positive components.

In this study, we examined the relationship between the novelty P3 and the P300 components of the brain event-related potential (ERP). Fifteen subjects responded manually to the rare stimuli embedded either in a classical auditory oddball series or in a series in which "novel" stimuli were inserted. The electroencephalogram (EEG) was recorded with a dense array of 129 electrodes. The data were analyzed by using spatial Principal Components Analysis (PCA) to identify a set of orthogonal scalp distributions, "virtual electrodes" that account for the spatial variance. The data were then expressed as ERPs measured at each of the virtual electrodes. These ERPs were analyzed using temporal PCA, yielding a set of "virtual epochs." Most of the temporal variance of the rare events was associated with a virtual electrode with a posterior topography, that is, with a classical P300, which was active during the virtual epoch associated with the P300. The novel stimuli were found to elicit both a classical P300 and a component focused on a virtual electrode with a frontal topography. We propose that the term Novelty P3 should be restricted to this frontal component.