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Comparison between auto-cross-correlation coefficients and coherence methods applied to the EEG for diagnostic
Marios Poulos1, Sozon Papavlasopoulos, Nikolaos Alexandris
1Department of Archive and Library Science, Ionian University, Elefterias Square, Palaia Anaktora, Greece. mpoulos@ionio.gr
Background:
Power-spectrum and coherence analysis of the EEG has often been applied in the study of various forms of brain dysfunction. The examination of differences in intra-hemispheric coherence and a novel method based on auto-cross-correlation algorithms between the left and right hemispheres of the same EEG are investigated in this paper.
Material/Methods:
Both coherence and the proposed method are computed from the same EEG segment across the EEG spectrum (0-64 Hz). In this experiment, five EEGs of different patients with severe brain damage were used. The novelty of this study lies in the fact that the autocorrelation coefficients are extracted in a particular spectrum, in contrast to the traditional coherence method, which is based on a measure of the square of the linear association between the two EEG signals from the entire EEG spectrum.
Results:
The results of the application of coherence and the proposed method showed that particular pairs of symmetrical cortex channels differed dramatically in specific damaged areas.
Conclusions:
Statistical analysis of the above results showed that the proposed method is more accurate than coherence because it could recognize the cases of the patients to a significant statistical degree, whereas the coherence method showed weakness in recognizing them.