EEG Alpha Asymmetry, Depression, and Cognitive Functioning

Ian H. Gotlib
Stanford University, Stanford, CA, USA

CharanRanganathand J. Peter Rosenfeld
Northwestern University, Evanston, USA

Davidson (1993) has proposed that hemispheric asymmetry in prefrontal activation, as measured by electroencephalographic (EEG) power in the alpha band (8± 13Hz), is related to reactivity to affectively valenced stimuli. David- son has proposed further that asymmetry is a stable trait, and that left frontal hypoactivation is a stable marker of vulnerability to depression.  In Study 1, we tested Davidson’ s formulations by examining differences in frontal EEG alpha asymmetry among currently depressed, previously depressed, and never depressed subjects. As expected, currently and previously depressed subjects showed left frontal hypoactivation relative to never depressed controls, but did not differ signifcantly from each other. In Study 2, we explored the associations among frontal EEG asymmetry, response to a negative mood induction procedure, endorsement of dysfunctional cognitions, and attentional processing of valenced stimuli. Contrary to predictions, frontal EEG asymmetry was unrelated to mood reactivity and cognitive functioning. Theoretical and methodological implications of these findings are discussed.

Functional connectivity in major depression: increased phase synchronization between frontal cortical EEG-source estimates

Sebastian Olbrich, Anja Tränkner, Tobias Chittka, Ulrich Hegerl, Peter Schönknecht
Psychiatry Research Neuroimaging (Impact Factor: 3.36). 01/2014; DOI:10.1016/j.pscychresns.2014.02.010

ABSTRACT Structural and metabolic alterations in prefrontal brain areas, including the subgenual (SGPFC), medial (MPFC) and dorsolateral prefrontal cortex (DLPFC), have been shown in major depressive disorder (MDD). Still it remains largely unknown how brain connectivity within these regions is altered at the level of neuronal oscillations. Therefore, the goal was to analyze prefrontal electroencephalographic phase synchronization in MDD and its changes after antidepressant treatment. In 60 unmedicated patients and 60 healthy controls (HC), a 15-min resting electroencephalogram (EEG) was recorded in subjects at baseline and in a subgroup of patients after 2 weeks of antidepressant medication. EEG functional connectivity between the SGPFC and the MPFC/DLPFC was assessed with eLORETA (low resolution brain electromagnetic tomography) by means of lagged phase synchronization. At baseline, patients revealed increased prefrontal connectivity at the alpha frequency between the SGPFC and the left DLPFC/MPFC. After treatment, an increased connectivity between the SGPFC and the right DLPFC/MPFC at the beta frequency was found for MDD. A positive correlation was found for baseline beta connectivity and reduction in scores on the Hamilton Depression Rating Scale. MDD is characterized by increased EEG functional connectivity within frontal brain areas. These EEG markers of disturbed neuronal communication might have potential value as biomarkers.