Analysis of Amplitude Modulation of EEG Based on Holo-Hilbert Spectrum Analysis During General Anesthesia

Objective: The study aims to investigate the relationship between amplitude modulation (AM) of EEG and anesthesia depth during general anesthesia. Methods: In this study, Holo-Hilbert spectrum analysis (HHSA) was used to decompose the multichannel EEG signals of 15 patients to obtain the spatial distribution of AM in the brain. Subsequently, HHSA was applied to the prefrontal EEG (Fp1) obtained during general anesthesia surgery in 15 and 34 patients, and the α-θ and α-δ regions of feature (ROFs) were defined in Holo-Hilbert spectrum (HHS) and three features were derived to quantify AM in ROFs. Results: During anesthetized phase, an anteriorization of the spatial distribution of AMs of α-carrier in brain was observed, as well as AMs of α-θ and α-δ in the EEG of Fp1. The total power (<inline-formula><tex-math notation="LaTeX">${\bm{P}}_{\bm{total}}$</tex-math></inline-formula>), mean carrier frequency (<inline-formula><tex-math notation="LaTeX">$\bm{M}{\bm{F}}_{\bm{C}}$</tex-math></inline-formula>) and mean amplitude frequency (<inline-formula><tex-math notation="LaTeX">$\bm{M}{\bm{F}}_{\bm{AM}}$</tex-math></inline-formula>) of AMs changed during different anesthesia states. Conclusion: HHSA can effectively analyze the cross-frequency coupling of EEG during anesthesia and the AM features may be applied to anesthesia monitoring. Significance: The study provides a new perspective for the characterization of brain states during general anesthesia, which is of great significance for exploring new features of anesthesia monitoring.