A 1H magnetic resonance spectroscopy imaging study on the working memory and brain biochemical metabolism in untreated obsessive-compulsive disorder patients comorbid with and without major depressive disorder

Abstract

Objective To investigate the differences of working memory and brain biochemical metabolism between untreated obsessive-compulsive disorder (OCD) patients comorbid with and without major depressive disorder (MDD) by proton magnetic resonance spectroscopy (1H-MRS). Methods Thirty-five patients with OCD, 38 patients with OCD comorbid MDD, and 41 healthy controls were studied in our study. 2-back, visual space memory test (VSMT), digit span test (DST) and Stroop color and word test (SCWT) were performed to evaluate working memory. And the 3 groups were also measured the levels of N-acetylaspartate (NAA), choline-containing compounds (Cho) and creatine (Cr) in frontal lobe and basal ganglia by using 1H-MRS, the ratios of NAA/Cr and Cho/Cr were calculated. Results The accurate answer number of 2-back task in both OCD patients comorbid with and without MDD were lower than that in healthy control (P=0.022, 0.049), and the completion time of VSMT ( (1 963±1 193) ms vs. (1 302±587) ms) and SCWT-C ( (16.6±4.2) s vs. (13.9±4.3) s) in OCD comorbid with MDD patients were longer than healthy controls (P=0.004, 0.007) .Also, OCD patients comorbid with MDD had lower score in VSMT, digit span forward, digit span backward and total DST than that in healthy controls (P=0.003, 0.020, 0.042, 0.006) . The NAA/Cr ratio in the left prefrontal white matter of OCD comorbid with MDD patients was significantly lower than that in healthy controls (2.07±0.40 vs. 2.32±0.33, P=0.017) . Conclusions OCD patients comorbid with MDD have verbal, visuospatial working memory impairments and inhibition dysfunction of central executive system, and OCD without MDD patients only have verbal working memory impairments. In addition, neuronal dysfunction in the left prefrontal white matter was found in OCD comorbid with MDD. Key words: Obsessive-compulsive disorder; Depressive disorder; Magnetic resonance spectroscopy; Comorbidity; Working memory