EEG hemispheric asymmetries during cognitive tasks in depressed patients with high versus low trait anxiety
Carlye B.G. Manna1,3, Craig E. Tenke1,2, Nathan A. Gates1,3, Jürgen Kayser1,2, Joan C. Borod3, Jonathan W. Stewart2, Patrick J. McGrath2, Gerard E. Bruder1,2
1Division of Cognitive Neuroscience, New York State Psychiatric Institute, New York, NY, USA; 2Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA; 3Department of Psychology and Neuropsychology Subprogram, Queens College and The Graduate Center of the City University of New York, Flushing, NY, USA
Received 25 March 2010; accepted 21 June 2010; published 18 October 2010.
Abstract
Studies of regional hemispheric asymmetries point to relatively less activity in left frontal and right posterior regions in depression. Anxiety has been associated with increased right posterior activity, which may be related to arousal and, in anxious-depressed individuals, offset the posterior asymmetry typically seen in depression. These asymmetries have been indexed by resting EEG or inferred through the use of lateralized auditory and visual tasks (e.g., dichotic listening and chimeric faces). However, associations between regional EEG activity and neurocognitive function in depression or anxiety remain unclear. The present study used matched verbal (Word Finding) and spatial (Dot Localization) tasks to compare task-related alpha asymmetries in depressed patients grouped according to level of trait anxiety. EEG and behavioral performance were recorded from depressed patients with high anxiety (n = 14) or low anxiety (n = 14) and 21 age- and education-matched healthy adults during the two tasks, and alpha power was averaged within each task. As predicted, the two patient groups exhibited opposite patterns of regional hemispheric alpha asymmetry. Greater right than left central-parietal activation was seen in the high-anxiety depressed group during the spatial task, whereas greater left than right frontal-central activation was found in the low-anxiety depressed group during the verbal task. Group differences in task performance were in the expected direction but did not reach statistical significance. These results are consistent with Heller's two-dimensional model of depression and anxiety and highlight the sensitivity of task-related EEG alpha in discriminating among subgroups of depressed patients differing in trait anxiety.
Key Words: depression, anxiety, EEG, alpha asymmetry, verbal/spatial processing