Related Experiment Video
Updated: Jun 16, 2026
12:03
A Method for Tracking the Time Evolution of Steady-State Evoked Potentials
Published on: May 25, 2019
Phase-compensated averaging for analyzing electroencephalography and magnetoencephalography epochs
Ayumu Matani1, Yasushi Naruse, Yasushi Terazono
1Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8561, Japan. matani@isp.ac
IEEE Transactions on Bio-Medical Engineering
|February 23, 2010
Summary
This study introduces phase-compensated averaging for electroencephalography (EEG) and magnetoencephalography (MEG) to analyze spontaneous brain activity. The novel method reveals directional phase-synchronizing relationships between brain regions, offering new insights beyond conventional techniques.
Area of Science:
- Neuroscience
- Signal Processing
- Biophysics
Background:
- Conventional stimulus-locked averaging in EEG/MEG treats spontaneous activity as noise, obscuring phase-related phenomena.
- Researchers studying long-distance synchronization, phase-reset, and event-related synchronization/desynchronization (ERD/ERS) require methods to analyze ongoing brain activity.
Purpose of the Study:
- To propose and evaluate a novel complex-weighted averaging method, phase-compensated averaging, for investigating phase-related phenomena in EEG/MEG data.
- To demonstrate the capability of phase-compensated averaging to selectively analyze phase-locked spontaneous activity and reveal directional phase-synchronizing relationships.
Main Methods:
- Developed a complex-weighted averaging technique (phase-compensated averaging) where EEG/MEG channels act as triggers by setting instantaneous phases to 0.
- Validated the method through simulations to assess its fundamental characteristics.
- Applied the method to analyze flash evoked potentials and reconstruct EEG/MEG time series.
Main Results:
- Simulations confirmed the method's ability to selectively average ongoing spontaneous activity phase-locked to each channel, evaluating directional phase-synchronizing relationships.
- Analysis of flash evoked potentials revealed directional phase-synchronizing relationships from frontal to occipital channels.
- The method recovered experimental sequence information potentially lost with conventional averaging and enabled direct visualization of long-distance synchronization and phase-reset.
Conclusions:
- Phase-compensated averaging is an effective technique for investigating phase-related phenomena in EEG/MEG data.
- The method enhances the understanding of brain connectivity by clarifying directional phase-synchronizing relationships.
- Event-related synchronization/desynchronization (ERD/ERS) can be interpreted as a consequence of phase-resetting events within the brain's spontaneous activity.
