White matter abnormalities are associated with the declined ability of reasoning and problem-solving in major depressive disorder.

Objectives: Executive function in people with depression is linked to the integrity of white matter fibers in the brain. We hypothesized that the maze tests in neuropsychological tests assessed reasoning and problem-solving abilities dependent on the integrity of brain white matter fibers, and assessed this relationship using diffusion tensor imaging (DTI) in depressed patients and healthy controls.

Methods: Participants aged from 18 to 50 years were recruited from Zhumadian Second People's Hospital from July 2018 to August 2019. The sample included 33 clinically diagnosed individuals with major depressive disorder (MDD) and 24 healthy volunteers (HVs). All subjects underwent Neuropsychological assessment battery (NAB) maze tests and DTI. Tract-based spatial statistics technology in FSL software was used to process DTI data, and threshold-free cluster enhancement (TFCE) was used to perform multiple comparison corrections. The fractional anisotropy (FA) of white matter fibers in the MDD group and HVs group were compared and extracted. Pearson correlation was used to analyze the relationship between FA and NAB scores and HAMD scores.

Results: The mean NAB maze test score for the MDD group was lower than the HVs group, and the difference was statistically significant (F = 11.265, p = .037). The FA value of the body of corpus callosum and cerebral peduncle right in the depression group was lower than that in the healthy control group, and the difference was statistically significant (p < .05). FA value of the body of corpus callosum was positively correlated with NAB score (r = 0.400, p = .036), but not with the HAMD score (r = 0.065, p = .723).

Conclusions: The decreased ability of reasoning and problem-solving in MDD may be due to the decreased integrity of the white matter fibers of the body of the corpus callosum.