Impaired upper alpha synchronisation during working memory retention in depression and depression following traumatic brain injury

Rates of major depressive disorder (MDD) following traumatic brain injury (TBI) are higher than in the general population. Individuals with depression following traumatic brain injury (TBI-MDD) exhibit working memory (WM) impairments. Electrophysiological evidence has suggested that parieto-occipital upper alpha synchronisation may enhance WM retention by inhibiting irrelevant processes. The current research assessed whether retention period WM parieto-occipital upper alpha activity is disrupted in groups with TBI-only (N = 20), MDD (N = 17), and TBI-MDD (N = 15) compared to healthy controls (N = 31). Behavioural data indicated poorer performance in MDD and TBI-MDD. Parietal-occipital upper alpha was reduced in the MDD and TBI-MDD groups, but was unaffected in TBI-only. These results suggest inhibitory deficits may account for WM impairments in MDD and TBI-MDD, and that for individuals with TBI-MDD it may be the depression rather than the TBI that impairs WM.