Power spectra and coherence in the EEG of a vegetative patient with severeasymmetric brain damage

Objectives: To examine differences in power spectra and intra-hemispheric c oherence between the left and right hemispheres in the presence of severe a symmetric brain damage. Methods: Power spectra and coherence functions were computed for a patient with severe damage to subcortical gray matter structures on the right side but relative preservation on the left. Results: Power spectra differed modestly over the hemispheres, with greater low frequency power and less high frequency power over the more damaged ri ght hemisphere. Coherence differed dramatically, with marked reduced cohere nce over the right hemisphere, particularly frontally where the damage was most extensive. Conclusions: Damage to subcortical structures of one hemisphere may result in a marked reduction in coherence in the ipsilateral EEG with only a modes t change in the power spectrum. We speculate that the physiologic basis of this selective change is damage to structures mediating communication betwe en cortical areas. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.