A Comparison of Surrogate Tests for Phase Synchronization Analysis of Neural Signals

Various studies show that advanced cognitive function is integrated by multiple interacted cortical regions. To investigate this mechanism, various measures, such as phase synchronization (PS) and partial directed coherence, has been applied to evaluate the pattern of neural connectivity among brain regions. However, some problems on quantifying neural connectivity are still open to be answered. For example, how to determine whether an estimated PS index (PSI) is significant big or not? Surrogate test is one main way to provide a threshold of significance for reference. Though many surrogate methods have been proposed, but which one is more suitable for PS analysis is not known yet. To deal with this question, this study performed a comparison of surrogate tests for the mean phase coherence based PSI with Electroencephalography (EEG) signals. Four different surrogate methods were compared, and results showed that among these methods, the rank-shuffled surrogate method is the most suitable one in providing significance test for PS analysis.