Study of heart-rate variability in a video task using Holo-Hilbert spectral analysis

•The effectiveness of using HHSA in analyzing the modulation and carrier frequencies of HRV was demonstrated.•The modulation and carrier frequencies in HRV was organized in a Holo-Hilbert spectrum (HHS) visualization.•The modulation frequency of very high-frequency band in HRV was analyzed.•The power of very high-frequency band in HRV can be an index to indicate the condition of sympathovagal balance. In this study, we applied the Holo-Hilbert spectral analysis (HHSA) method to analyze HRV in electrocardiography (ECG) signals. The HHSA intends to interpret the measured interbeat-interval (IBI) signal as the multiplication of an oscillatory signal (carrier wave) with a modulatory signal (envelope wave). Instantaneous frequency analysis (IFA) was adopted to calculate the frequency modulation (FM) and amplitude modulation (AM) frequencies at each time point. The probability of FM-AM distribution across the whole measured IBI signal was accumulated and displayed on a Holo-Hilbert spectrum (HHS). Twenty healthy subjects were recruited in our ECG study. Each subject was requested to view two video clips, including one relaxing video clip and one horror video clip. We observed the very high-frequency (VHF) band was modulated by a ∼0.05 Hz AM frequency on the calculated HHS. The value of VHF power was significantly decreased (p