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On the recording reference contribution to EEG correlation, phase synchrony, and coherence.

Sanqing Hu¹, Matt Stead, Qionghai Dai

¹Department of Neurology, Division of Epilepsy and Electroencephalography, Mayo Clinic, Rochester, MN 55905, USA. Sanqing.Hu@drexel.edu

IEEE Transactions on Systems, Man, and Cybernetics. Part B, Cybernetics : a Publication of the IEEE Systems, Man, and Cybernetics Society

|January 29, 2010

Summary

The recording reference signal significantly impacts electroencephalography (EEG) measures like correlation, phase synchrony, and magnitude squared coherence (MSC). Understanding this influence is crucial for accurate analysis of brain signal synchronization.

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Area of Science:

Neuroscience
Signal Processing
Biomedical Engineering

Background:

Electroencephalography (EEG) signal synchronization is often assessed using correlation, phase synchrony, and magnitude squared coherence (MSC).
Previous research indicates that the choice of recording reference signal can confound the interpretation of these synchronization measures.
Standard EEG montages like bipolar and average reference do not fully resolve the issue of reference signal influence.

Purpose of the Study:

To analyze the impact of reference signal amplitude and power on EEG signal correlation, phase synchrony, and MSC.
To investigate the contribution of the recording reference on bivariate measures in referential intracranial EEG (iEEG) recordings.
To demonstrate the significant influence of the recording reference on synchronization analysis.

Main Methods:

Mathematical analysis of the influence of reference signal amplitude and power on correlation, phase synchrony, and MSC.
Application of a previously developed method to identify and extract reference signal contribution in iEEG.
Experimental investigation using referential iEEG data from human subjects.

Main Results:

Reference signal amplitude variations can cause non-monotonic changes in phase synchrony and correlation, with even small amplitude changes having significant effects.
Reference signal power variations can lead to non-monotonic changes in MSC, decreasing to zero before increasing to one.
High amplitude or power reference signals consistently increase correlation, phase synchrony, and MSC values.

Conclusions:

The recording reference signal critically affects EEG synchronization measures (correlation, phase synchrony, MSC).
Reference signal characteristics (amplitude, power) can either enhance or diminish observed synchronization.
Accurate interpretation of EEG synchronization requires careful consideration and potential correction for reference signal contributions.