Abstract
Quantitative EEG analysis was done on 29 medicated right-handed depressive patients at age over 45 and age and sex matched right-handed 20 normal controls. The patients were all diagnosed as major depression with melancholia by DSM-III-R and were divided into anxiety type (n=17) and retardation type (n=12) evaluated with the Hamilton rating scale for depression.
Eye closed resting EEGs were recorded on a data recorder from the 16 electrode leads (10-20 system). Artifact rejected 3 minutes EEGs were analyzed by off-line with Fast Fourier Transform from the bilateral frontal (F3, F4), parietal (P3, P4) and occipital (O1, O2) regions. The mean values of absolute amplitude power (μV) and the mean Z scores of inter-, and intrahemispheric coherence were obtained in theta 1 (4.0-6.0 Hz), theta 2 (6.0-8.0 Hz), alpha 1 (8.0-10.5 Hz), alpha 2 (10.5-13.0 Hz), beta 1 (13.0-20.0 Hz), and beta 2 (20.0-40.0 Hz) frequency bands respectively.
The main findings were:
1) Beta 1 and beta 2 power were greater in patients with anxiety type depression than in normal controls, and the differences were statistically significant over the parietal and occipital regions in beta 1 and the frontal region in beta 2. The anxiety type was distin-guished from the retardation type with the increase of beta 2 power. The retardation type showed higher alpha 1 power over the frontal region and lower alpha 2 power over the occipital region than normal controls.
2) Both types showed greater frontal predominant ratio to the parietal in beta 2 power than did normal controls. The retardation type was distinguished from the anxiety type with the right predominance in beta 1 power over the frontal region.
3) Both groups of patients showed lower frontal interhemispheric coherences than normal controls in each band. In particular, the anxiety type showed significantly lower alpha 2 band and lower beta 1 and beta 2 bands. The parietal interhemispheric coherence was lower in the anxiety type but higher in the retardation type than in normal controls in each band, and this difference was prominent in theta 2 band.
4) The two groups of patients showed higher fronto-parietal intrahemispheric coher-ences in both hemispheres than the normal controls in each band. Especially, the anxiety type showed higher in theta 2 and alpha 1 bands.
5) These results suggest that the depressive patients have abnormal inter- and intra-hemispheric functions, including hypofrontality, and that there may be those differences between the anxiety type and the retardation type.
