α Power, α asymmetry and anterior cingulate cortex activity in depressed males and females

Abstract

Left fronto-cortical hypoactivity, thought to reflect reduced activity in approach-related systems, and right parietal hypoactivity, associated with emotional under-arousal, have been noted in major depressive disorder (MDD). Altered theta activity in the anterior cingulate cortex (ACC) has also been associated with the disorder. We assessed resting frontal and parietal alpha asymmetry and power in non-medicated MDD (N = 53; 29 females) and control (N = 43; 23 females) individuals. Theta activity was examined using standardized low-resolution electromagnetic tomography (sLORETA) in the ACC [BA24ab and BA32 comprising the rostral ACC and BA25/subgenual (sg) ACC]. The MDD group, and particularly depressed males, displayed increased overall frontal and parietal alpha power and left midfrontal hypoactivity (alpha(2)-indexed). They also exhibited increased sgACC theta(2) activity. MDD females had increased right parietal activity, suggesting increased emotive arousal. Thus, unmedicated depressed adults were characterized by lower activity in regions implicated in approach/positive affective tendencies as well as diffuse cortical hypoarousal, though sex specific modulations emerged. Altered theta in the sgACC may reflect emotion regulation abnormalities in MDD.

Figure 1

Anterior cingulate cortex (ACC) regions of interest (ROIs). Top panel: ROI consisting of voxels from BA24. Middle panel: ROI consisting of voxels from BA25 (subgenual ACC). Bottom panel: ROI consisting of voxels in BA32.

Figure 2

Midfrontal alpha₂ asymmetry in the Major Depressive Disorder (MDD) and control groups (sex collapsed; *p<.05). Negative values reflect greater left alpha₂ power (i.e., decreased relative left cortical activity); positive values reflect greater right alpha₂ power (i.e., decreased relative right cortical activity).

Figure 3

Parietal alpha₂ asymmetry in the females and males with Major Depressive Disorder (MDD) (*p<.05). Negative values reflect greater left alpha₂ power (i.e., decreased relative left cortical activity or, conversely, increased relative right cortical activity); positive values reflect greater right alpha₂ power (i.e., decreased relative right cortical activity).

Figure 4

Theta₂ activity in BA25/subgenual anterior cingulate cortex (sgACC) in the Major Depressive Disorder (MDD) and control groups (sex collapsed; *p<.05).