A neuronal fiber tracking study for major depressive disorder using MR diffusion tensor imaging with fiber tractography

Diffusion tensor imaging (DTI) had been proved to be a powerful tool to investigate the white matter integrity and visualize the neuronal axons in vivo. Most of the DTI-based studies mainly used the region-of-interest approach to investigate the abnormalities in areas of white matter tracts involved in mood regulation for patients with major depressive disorder (MDD). In this study, we explored the structure of the fiber connections in whole-brain white matter for both major depressive patients and healthy subjects based on the DTI tractography. With the automatic anatomical labeling (AAL) process, each individual brain can be partitioned into ninety regions in normalized space so that the number of the connected fibers and histograms of the fiber lengths between any paired regions can be estimated. Twenty-three MDD patients and twenty-four age and gender-matched normal subjects were recruited. Our results concluded that: 1) the numbers of connected fibers revealed significant increase (pvalue <; 0.005) in the MDD group compared with the normal group in mood-regulation related region pairs consisting of right superior frontal gyrus to right pallidum, right putamen to right precuneus, left pallidum to left precuneus, left superior parietal gyrus to right superior occipital gyrus, left middle occipital gyrus to right middle temporal gyrus, and both side lingual gyrus to both side superior temporal gyrus. Only two region pairs manifested significant decrease (p-value <; 0.005) in patient group, which were right insula to right superior temporal gyrus, and right precuneus to right inferior temporal gyrus; 2) the distributions of the connected fiber lengths for the detected region pairs with the increasing or decreasing fibers in MDD group were between 10 to 30 mm.