Quantification of Pseudo-Periodicity of Alpha Rhythm in Meditation EEG
As meditation demonstrates its significant healing power, researchers have been trying to find a more scientific way to study the mechanism. In our study of Zen meditation EEG (electroencephalogram), variation of alpha rhythmic frequency is considered as an important index to be monitored in the beginning of meditation session. It might be related to different meditation stages corresponding to various degrees of mindfulness states. Reliable estimate of the alpha rhythmic variation becomes crucial to the exploration of meditation scenario. Conventional methods for spectral analysis hardly discriminate subtle variation of alpha frequency. This paper describes a method based on the periodicity transform (PT) to track the time-varying, instantaneous frequency of alpha rhythm by analyzing the running principal period (RPP). The method is thus abbreviated as PBFT (period-based frequency tracker). Compared with the short-time Fourier transform (STFT) widely applied to the EEG, the proposed method contributes clearer and more proper results about the frequency variation of alpha rhythms and is useful to the study on meditation EEG.