Brain electrical asymmetries during cognitive task performance in depressed and nondepressed subjects.
BACKGROUND
Studies using electroencephalogram (EEG) measures of activation asymmetry have reported differences in anterior asymmetry between depressed and nondepressed subjects. Several studies have suggested reciprocal relations between measures of anterior and posterior activation asymmetries. We hypothesized that depressed subjects would fail to show the normal activation of posterior right hemisphere regions in response to an appropriate cognitive challenge.


METHODS
EEG activity was recorded from 11 depressed and 19 nondepressed subjects during the performance of psychometrically matched verbal (word finding) and spatial (dot localization) tasks. Band power was extracted from all epochs of artifact-free data and averaged within each condition. Task performance was also assessed.


RESULTS
Depressed subjects showed a specific deficit in the performance of the spatial task, whereas no group differences were evident on verbal performance. In posterior scalp regions, nondepressed controls had a pattern of relative left-sided activation during the verbal task and relative right-sided activation during the spatial task. In contrast, depressed subjects failed to show activation in posterior right hemisphere regions during spatial task performance.


CONCLUSIONS
These findings suggest that deficits in right posterior functioning underlie the observed impairments in spatial functioning among depressed subjects.
Henriques
J B
JB
Department of Psychology, University of Wisconsin-Madison 53706, USA.
Davidson
R J
RJ
D000328:Adult; D003071:Cognition / Q000502:physiology*; D003866:Depressive Disorder / Q000503:physiopathology* / Q000523:psychology; D004569:Electroencephalography; D004594:Electrophysiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D014705:Verbal Behavior