A three-dimensional reconstruction of the R-R interval (RRI) signal extracted from the continuous electrocardiogram (ECG) signals in phase space for a different individual (B) under various external and internal stimulation conditions: (a) baseline (B1) RRI before control drink administration, (b) baseline (B2) RRI after control drink administration, (c) negative picture cue exposure after control drink administration, and (d) paced breathing after control drink administration. Phase space data were plotted with a delay parameter of 1 and embedding dimension parameters of 3 (B2 baseline), 4 (B1 baseline and negative picture cue exposure), and 5 (paced breathing).