Performance of different synchronization measures in real data: A case study on electroencephalographic signals.

We study the synchronization between left and right hemisphere rat electroencephalographic ~EEG! channelsby using various synchronization measures, namely nonlinear interdependences, phase synchronizations, mutualinformation, cross correlation, and the coherence function. In passing we show a close relation betweentwo recently proposed phase synchronization measures and we extend the definition of one of them. In threetypical examples we observe that except mutual information, all these measures give a useful quantificationthat is hard to be guessed beforehand from the raw data. Despite their differences, results are qualitatively thesame. Therefore, we claim that the applied measures are valuable for the study of synchronization in real data.Moreover, in the particular case of EEG signals their use as complementary variables could be of clinicalrelevance.