Systematic Review of the Literature, and an Investigation of the Roles of Severity, Gender and Cerebral Sites, in the relationship Between Alpha Electroencephalographic Asymmetry and Depression

Abstract

The approach-withdrawal model of depression hypothesizes that depression is characterized by: (i) behavioural withdrawal from negative aversive stimuli (which is associated with increased activation of the right frontal lobe) and (ii) reduced interaction with positive pleasant stimuli (which is evidenced by reduced activation of the left frontal lobe). Therefore, depressed individuals show greater activation in the right vs the left frontal lobes. However, experimental findings in this field of research have shown some inconsistencies in depressed participants. To investigate these inconsistencies, this thesis focused on two tasks. First, a comprehensive review of the literature on the occurrence of alpha EEG asymmetry in depression was undertaken. From this, three important issues which affect the occurrence of alpha EEG asymmetry were identified vis-à-vis the roles of: (i) depression severity, (ii) gender, and (iii) cerebral locations where alpha asymmetry occurs (i.e., frontal, temporal, parietal and occipital sites). Therefore, the second section of this thesis comprises an investigation of the relationship between alpha EEG asymmetry and these three issues.