Thalamic metabolic rate predicts EEG alpha power in healthy control subjects but not in depressed patients

Background: EEG alpha power has been demonstrated to be inversely related t o mental activity and has subsequently been used as an indirect measure of brain activation, The hypothesis that the thalamus serves as a neuronal osc illator of alpha rhythms has been supported by studies in animals, but only minimally by studies in humans. Methods: In the current study, PET-derived measures of regional glucose met abolism, EEG, and structural MRI were obtained from each participant to ass ess the relation between thalamic metabolic activity and alpha power in dep ressed patients and healthy controls. The thalamus was identified and drawn on each subject's MRI, The MRI was then co-registered to the corresponding PET scan and metabolic activity front the thalamus extracted Thalamic acti vity was then correlated with a 30-min aggregated average of alpha EEG powe r: Results: Robust inverse correlations were observed in the control data, ind icating that greater thalamic metabolism is correlated with decreased alpha power No relation was found in the depressed patient data. Conclusions: The results are discussed in the context of a possible abnorma lity in thalamocortical circuitry associated with depression. (C) 1999 Soci ety of Biological Psychiatry.