Directed coherence as a measure of interhemispheric correlation of EEG.

Based on a bidirectional model and the temporal relation of the signals, directed coherence is defined to describe the EEG correlation according to the direction of information transmission in the frequency domain. The interhemispheric directed coherences of EEG pairs in the prefrontal, frontal, central, parietal and occipital cortices were investigated. Statistically, significantly greater right-left directed coherences were found in the parietal and occipital regions than that of the left-right direction for alpha activity. The results indicate different information processing for different frequency bands between the left and right hemispheres, and this can not be derived from the examination of original coherence. This may suggest that the measure of directed coherence can provide more information than that of original coherence.