The degree of the brain structural white matter networks in the first–episode and recurrent depressed patients

Abstract

Objective To explore the differences of the degree indicating the density of the connectivity of nodes between the brain structural white matter networks in the first–episode (FD), recurrent (RD) depressed patients and the healthy control (HC) subjects. Method The diffusion tensor imaging data were obtained from 29 FD patients, 20 RD patients and 57 HC subjects. The whole cerebral cortex was divided into 90 regions by the anatomical label map. Fiber tracking was performed in the whole cerebral cortex of each subject to reconstruct white matter tracts of the brain using the fiber assignment by continuous tracking algorithm. And then the brain structural networks were constructed using the complex network theory. The nodal degree of the brain networks of FD and RD were compared with that of HC, and then the correlations between the degree of the significant nodes and the clinical features of patients were explored. Result The degree of the nodes in the networks of FD descended significantly in the left putamen (11.83±2.28) when compared with HC (13.95±2.33; t=–4.02; P=0.000 13, survived correction). That of RD descended significantly (the right dorsolateral superior frontal gyrus (7.80 ± 1.43); the left putamen (11.75±2.07) when compared with HC (9.70 ± 2.89, 13.95 ± 2.33; t= –3.81, –3.73; P=0.000 31, 0.000 37, survived correction). That of RD descended significantly in the right dorsolateral superior frontal gyrus (7.80 ± 1.43) when compared with FD (9.62±1.78; t=–3.80; P=0.000 42, survived correction). The distribution of the hub regions in the patient and healthy were similar and the left putamen was the same hub region for both groups. Significant negative correlations were found between the degree of the right dorsolateral superior frontal gyrus and the number of episodes (r=–0.42, P=0.002 6) and the course of the disease (r=–0.41, P=0.003 7) in the patient. Conclusions The degree of the connectivity between the frontal region and putamen are possibly decreased in the depressed patient. The left putamen is in the importance role in the brain network and the damage of its connected fibers may be the common structural changes in both FD and RD. The damage of the fibers connected to the frontal region is related with the recurrent course of the depressed patients. Key words: Depressive disorder; First episode; Recurrent; Diffusion tensor imaging; Brain structural network