Interhemispheric asymmetry of EEG coherence as a reflection of different functional states of the human brain.

EEG coherence analysis was used to study aspects of the synchronisation of electrical processes in the left and right cerebral hemispheres of right-handed and left-handed healthy subjects in a state of calm wakefulness. Right-handed subjects showed a greater coherence in the left hemisphere and left-handed subjects in the right hemisphere. There were also differences between right-handed and left-handed subjects in the regional profiles of interhemispheric asymmetry and in the interhemispheric asymmetry of individual spectral bands. These differences may reflect variations in the involvement of cortical and subcortical cerebral structures in the formation of the hemispheric specificity. Changes in interhemispheric coherence with the onset of drowsiness were also observed. This suggests that changes in the interconnections of neural networks are also involved in changes in arousal. Certain characteristic regional interhemispheric asymmetry patterns and asymmetries in the spectral bands appear to be necessary for normal human brain function.