  There is mounting evidence of a link between the properties of
electroencephalograms (EEGs) of depressive patients and the outcome of
pharmacotherapy. The goal of this study was to develop an EEG biomarker of
antidepressant treatment response which would require only a single EEG
measurement. We recorded resting, 21-channel EEG in 17 inpatients suffering
from bipolar depression in eyes closed and eyes open conditions. The EEG
measurement was performed at the end of the short washout period which followed
previously unsuccessful pharmacotherapy. We calculated the normalized wavelet
power of alpha rhythm using two referential montages and an average reference
montage. In particular, in the occipital (O1, O2, Oz) channels the wavelet
power of responders was up to 84% higher than that of nonresponders. Using a
novel classification algorithm we were able to correctly predict the outcome of
treatment with 90% sensitivity and 100% specificity. The proposed biomarker
requires only a single EEG measurement and consequently is intrinsically
different from biomarkers which exploit the changes in prefrontal EEG induced
by pharmacotherapy over a given time.
