Regional brain functions in the resting state indicative of potential differences between depression and chronic pain

Abstract

Complex relationships between depression and chronic pain have been reported in previous studies. However, only a few neuroimaging studies have investigated similarities and differences in neural systems underlying them. We examined the brain functions in the resting state of 43 patients with depression, 41 patients with chronic pain (somatoform pain disorder) and 41 healthy controls, by using regional homogeneity (ReHo) and functional connectivity analysis. Depressive symptoms were assessed by using the Beck Depression Inventory-Second Edition (BDI-II). ReHo values for the dorsolateral prefrontal cortex (DLPFC) significantly decreased for chronic pain patients, and functional connectivity between the DLPFC and thalamus decreased only for these patients. These findings are indicative of distinct brain functions related to depression and chronic pain. Understanding these differences would further elucidate the pathophysiology of these conditions.

Figure 1

ReHo values for one sample t-test (A) for patients with depression, (B) for patients with chronic pain, and (C) for healthy controls.

Figure 2

(A) Different ReHo values in the DLPFC are shown (p (FWE corrected) < 0.05). Scatter-plots illustrate these correlations. *p < 0.01, Bonferroni post hoc test. DLPFC; dorsolateral prefrontal cortex, D; depression, C; chronic pain and H; healthy controls. Each error bar represents one standard error. (B) Hypoconnectivity in the DLPFC and thalamus is noted in the chronic pain patients (p (FWE corrected) < 0.05). Scatter-plots illustrate these correlations. *p < 0.01, Bonferroni post hoc test. Each error bar represents one standard error.