A near-infrared spectroscopy study of brain activation during the Verbal Fluency Task and the Tower of London Test in patients with major depressive disorder

Abstract

Objective To explore the correlation between depression and brain activation in patients with major depressive disorders(MDD) during the Verbal Fluency Task(VFT) and the Tower of London Test(TOL) using near-infrared spectroscopy(NIRS). Methods Thirty-five depression patients and thirty-five healthy controls matched with age and sex were both measured of oxygenated hemoglobin concentration(oxy-Hb) changes in the prefrontal cortex (PFC) by NIRS during VFT and TOL tasks. The severity of depression and anxiety symptoms were assessed by Hamilton Rating Scale for Depression (HAMD), Hamilton Anxiety Rating Scale (HAMA) and Beck Depression Rating Scale(BDI). The average [oxy-Hb] changes in each region of interest (ROI) were compared between the two groups by using an independent sample t test. Then the correlation between the average (oxy-Hb) changes of ROI during the task tests and the scores of HAMD、HAMA and BDI was explored by Spearman analysis in MDD group. Results During VFT and TOL, the average (oxy-Hb) changes in ROI of dorsolateral PFC and the ventrolateral PFC were significantly lower in MDD group ((0.18±0.19) mmol·mm vs. (0.29±0.22) mmol·mm, (-0.01±0.16) mmol·mm vs. (0.08±0.14) mmol·mm; t=-2.195,P=0.032, t=-2.448,P=0.017). The Spearman correlation analysis found that the average (oxy-Hb) changes in the frontopolar of MDD during TOL were negatively associated with the total scores of HAMD and BDI(r=-0.354, P=0.037; r=-0.495,P=0.003), and the average (oxy-Hb) changes in the left lateral PFC in MDD during TOL were negatively associated with the total scores of BDI (r=-0.349, P=0.040). Conclusions The function of frontopolar and lateral PFC in MDD is significantly impaired. Activation in the frontopolar and the left lateral PFC during TOL task will be much less if the depression becomes more severe. By using NIRS, TOL may be a good active task to measure the brain function. Key words: Depressive disorder; Spectroscopy near-infrared; Verbal fluency task; Tower of London test