M-ECG: extracting heart signals with a novel computational analysis of magnetoencephalography data

Figures

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  Figure 1. The preprocessing pipeline used in this study to isolate MEG-derived electrocardiogram (M-ECG) signals, including cardiac independent component (C-IC), independent electrocardiogram (I-ECG), and reference channel (REF).

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  Figure 2. Automatically detected valid R-peaks for reference channel (REF) (A) and cardiac independent component (C-IC) (B) for participant 1 (280–300 s). Red dots indicate the detected valid peaks on each signal.

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  Figure 3. Original vs. corrected RR intervals for reference channel (REF) (A) and cardiac independent component (C-IC) (B) for participant 1 (0–360 s). The corrected signal is shown in red, while the uncorrected signal appears in blue.

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  Figure 4. Comparison of the averaged peak-to-peak reference channel (REF), cardiac independent component (C-IC), and independent electrocardiogram (I-ECG) signals for participant 1. REF is shown in red, C-IC in green, and I-ECG in blue.

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  Figure 5. Dynamic time warping (DTW) of RR intervals (seconds) with independent electrocardiogram (I-ECG) vs. reference channel (REF) (A), and I-ECG vs. cardiac independent component (C-IC) (B) for participant 1. The lower the DTW value, the more similar the two signals are, with a value closer to zero indicating a better alignment and higher similarity.

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  Figure 6. The continuous wavelet transform (CWT) analysis using the Morlet wavelet reveals time–frequency patterns in independent electrocardiogram (I-ECG) (A), cardiac independent component (C-IC) (B), and reference channel (REF) (C) signals from participant 1, with recurrent high-power bursts over 20 s corresponding to R waves.

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  Figure 7. Power spectral density (PSD) between reference channel (REF), cardiac independent component (C-IC), and independent electrocardiogram (I-ECG) RR intervals for participant 1 (0–360 s). Low frequency (LF) and high frequency (HF) bands are analyzed across REF (blue), C-IC (orange), and I-ECG (green) signals. Very-low-frequency (VLF) band is shown for completeness but is not interpreted due to short recording duration.