The EEG and differential diagnosis in psychogeriatrics.

A model for differentiating cerebral dysfunction in senile, arteriosclerotic dementia, and depressive states is proposed on the basis of electrocortical topographic measures of EEG coherence. Bipolar EEGs were recorded from central, parietal, occipital and temporal areas in 24 elderly patients with a firm clinical diagnosis of senile dementia, senile arteriosclerosis or depression. Power and coherence spectra were computed on 20 second epochs recorded during eyes open, eyes closed and photic stimulation. Significant group differences were reported in both power and coherence measures. Power results were uniform for all channels but coherence values differed significantly with derivation. The best discriminator between groups was EEG coherence estimates between right parietal and temporal derivation. Correlations between clinical symptomatology and EEG coherence supported the direction of the discrimination between groups. The EEG coherence function is discussed as a potential measure of neuro-functional pathology in psychiatry.