EEG coherence and power in the discrimination of psychiatric disorders and medication effects

Electroencephalogram (EEG) coherence (COH) and power measures were included in a series of stepwise discriminant analyses to determine which variables were most sensitive in the differentiation of four psychiatric inpatient groups and two major classes of psychotropic medication. Eight channels of eyes-closed, bipolar EEG activity were recorded from 74 inpatients (paranoid schizophrenics, dysthymics, major affectives receiving tricyclics, neuroleptics, or no medication, and geriatrics). Discriminant analyses were conducted for theta, alpha, and fast beta frequency bands for power variables, COH variables, and the resultant significant power and COH discriminating variables. Without exception, COH measures, usually in the alpha band, were more sensitive than power measures in differentiating the various groups. Results suggested that COH decreases with age, is greatest in paranoid schizophrenics, decreases with neuroleptic medication, and increases with tricyclic antidepressants. Group differences were interpreted in accordance with an arousal model for COH.