Striatal hypoactivation and cognitive slowing in patients with partially remitted and remitted major depression

The present pilot study investigated neuronal correlates of executive functioning in patients previously diagnosed with recurrent major depressive disorder (MDD). The aim of the study was to examine a partially remitted and remitted MDD patient group with functional magnetic resonance imaging (fMRI) using a cognitive activation paradigm in order to probe aspects of response inhibition, attention shift, and working memory. Twenty MDD patients and 19 healthy controls, matched for age and sex, participated in the study. A working memory n-back task with single presentations of incongruent Stroop words was used, with the instruction to either remember the color of the ink the word was written in, or the color word itself, presented two or three words back in the presentation series. MR images were acquired on a 1.5-T GE Signa HD MR scanner. In addition to MR data, response time (RT) and response accuracy (RA) behavioral data were recorded. The behavioral results showed longer RT and lower RA in the MDD group compared to the control group across instruction conditions and working memory load. Based on previous studies of executive function, a composite region of interest (ROI) mask of the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC), caudate, and putamen was used in statistical analysis. Significant activation was observed in controls throughout this corticostriatal network. When compared to controls, patients showed no significant difference in the level of activation in the ACC and the DLPFC. However, in the putamen and caudate, hypoactivation in the patient group was observed. It was concluded that these effects could be due to a scar effect as a result of previous episodes of MDD.