Figure 1. The schematics of global analysis.

Spatiotemporally processed signals recorded from multiple points on a line, showing staggered action potentials upstrokes consistent with wavefront propagation (A). Same signals as A shifted to align the upstrokes (B). The first principle component $\left(W_1\right)$ displays alternans (C). Spectrogram of C, showing a 1:2 peak of alternans (D). The second principle component $\left(W_2\right)$ displays more pronounced alternans larger than C (E). Spectrogram of E, shows a prominent 1:2 peak of alternans (F). The bar in A depicts 200 ms.