EEG Alpha Asymmetry, Depression, and Cognitive Functioning

Davidson (1993) has proposed that hemispheric asymmetry in prefrontal as measured by electroencephalographic (EEG) power in the alpha (8-13Hz), is related to reactivity to affectively valenced stimuli. Davidson has proposed further that asymmetry is a stable trait, and that left frontal is a stable marker of vulnerability to depression. In Study 1, we Davidson's formulations by examining differences in frontal EEG alpha among currently depressed, previously depressed, and never subjects. As expected, currently and previously depressed subjects left frontal hypoactivation relative to never depressed controls, but did differ significantly from each other. In Study 2, we explored the associations among frontal EEG asymmetry, response to a negative mood induction endorsement of dysfunctional cognitions, and attentional processing of valenced stimuli. Contrary to predictions, frontal EEG asymmetry was to mood reactivity and cognitive functioning. Theoretical and implications of these findings are discussed.