Statistical detection of between-group differences in event-related potentials

Objective: Many event-related potential (ERP) situations do not fulfill the multivariate statistics requirement of more cases than measurements. Five simulation studies were carried to select a sensitive test for comparing tw o independent groups of ERPs. Methods: Simulated signal and noise waveforms were generated using differen t combinations of parameters: cases or replications per group, correlation between data points, number of points, signal-to-noise ratio (S/N), etc. Th e false alarm (FA) rate of each method was assessed and their sensitivity c ompared over sets of 2000 simulated experiments per condition. Results: Study 1 identified the 'Projection onto Centroids Difference Vecto rs' (PCDV) method of Haig and Gordon (Brain Topogr 1995;8:67) as very good, but its FA rate was erratic under several conditions. The following studie s served to shape the implementation parameters of a version of PCDV, terme d PCDVp, that assesses significance through random permutations of the case labels. The final form is very sensitive. For instance, with two groups of 48 trials of 30-point EEG-like waveforms, its power for alpha = 0.05 is ab out 50% at S/N 1.0 and 90% at S/N 1.5 (amplitude). Conclusion: PCDVp requires no a priori knowledge and is sensitive to detect differences between independent sets of waveforms, topographies or spatio- temporal data. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.