Event-related calculation of band power changes can be used to quantify event-related desynchronization, event-related synchronization, and event-related coherence (ERCoh). It is shown that in the case of a motor task especially, the ERCoh time course depends on the type of EEG derivation used, whereby referenced EEG data can result in a bilateral coherence increase, although both hemispheres generate independent sensorimotor rhythms. It is further shown that not only Rolandic mu rhythms but also central beta rhythms display a lack of interhemispheric linear phase coupling.
Department of Medical Informatics, Institute of Biomedical Engineering, and Ludwig Boltzmann Institute for Medical Informatics and Neuroinformatics, Technical University Graz, Austria; and *Department of Biomedical Engineering, Faculty of Health Sciences, University of Cape Town, South Africa
Address correspondence and reprint requests to Gert Pfurtscheller, Department of Medical Informatics, Institute of Biomedical Engineering and Ludwig Boltzmann Institute for Medical Informatics and Neuroinformatics, Technical University Graz Inffeldgasse 16a/II, A-8010 Graz, Austria.
This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung in Austria, Projekt P11571-MED.
1 In earlier publications the following definition was used: MATH 1
With this definition, negative numbers are obtained for ERS %. Because ERD is defined as power decrease and ERS as power increase, it is more precise when the following expression is used: MATH 2