Fig. 1.

(A) Workflow for determining and correcting the phase shift to enhance the correlation between the internal and external waveforms. Three quantitative phase-domain methods were applied, including phase-space oval fitting (POF), principal component analysis (PCA), and analytical signal analysis (ASA). The correlation between the phase-shift–corrected external and internal waveforms was compared with the original correlation and to the waveforms' maximum time-domain cross-correlation (TCC). (B) Representative ellipse and principal components found for participant 2 through the POF and PCA methods, respectively. (C) Representative instantaneous phases of and the phase shift between (inset) the internal and external waveforms calculated for participant 2 using the ASA method. Abbreviations: Ext = external; Int = internal.