Abstract:

Since the introduction of the time-frequency analysis technique into the field of EEG data in the 1980’s, researchers can excavate non-phase locked components in EEG signals, overcoming the previous shortcomings of traditional ERP methods. In the field of psychology, the two most commonly used time-frequency analysis methods are wavelet transform and Hilbert transform. Power, phase locking index (PLI), and coherence are three important indices of time-frequency analysis. Power in different frequency band is typically considered to reflect different mental processes. For example, α power is frequently related to selective attention, while γ energy is often associated with feature binding. Researchers use PLI to investigate the mechanism generated by an ERP component. Coherence indicates the exchange of information between long-distance brain regions and cognitive control of higher-level brain regions in the low-level brain regions, which show different patterns in various complex cognitive tasks.

Key words: time-frequency analysis, wavelet transform, Hilbert transform, power, PLI, coherence