Pattern of impaired working memory during major depression

BACKGROUND: The aim of this study was to assess working memory (WM) in patients with major depressive disorder (MDD), using a robust parametric WM task (the n-back task). METHODS: Twenty patients with MDD and twenty healthy controls completed a visual version of the paradigm, comprising four levels of task difficulty (i.e. 0-, 1-, 2-, and 3-back). Performance accuracy and reaction time (RT) were measured at each difficulty level. RESULTS: In comparison with controls, patients with MDD exhibited slower RTs (F((1,38)) = 25.16, p < 0.001), and reduced accuracy (F((1,38)) = 5.93, p < 0.001). There was no diagnosis-specific effect of task difficulty on performance accuracy. However, the faster response to memory (1-3-back) than to shadowing (0-back) tasks observed in controls was not as pronounced in patients. CONCLUSIONS: These observations support a relatively specific impairment of WM/central executive function in MDD, which may potentially mediate the diverse pattern of cognitive dysfunction noted in MDD. The parametric n-back task is applicable to subjects with MDD and yields results interpretable across the dimensions of task difficulty and performance in controls and patients.