Desynchronized white matter function and structure in drug-naive first-episode major depressive disorder patients

Abstract

BackgroundMajor depressive disorder (MDD) is a highly prevalent mental disease. Using magnetic resonance imaging (MRI), although numerous studies have revealed the alterations in structure and function of grey matter (GM), few studies focused on the synchronization of white matter (WM) structure and function in MDD. The aim of this study was to investigate whether functional and structural abnormalities of WM play an essential role in the neurobiological mechanisms of MDD.MethodsGradient-echo imaging sequences at 3.0T were used to gather resting state functional MRI (rsfMRI) data, which were performed on 33 drug-naive first-episode MDD patients and 34 healthy controls (HCs). After data preprocessed, amplitude of low frequency fluctuation (ALFF) of WM was calculated. ALFF values in different frequency bands were analyzed, including typical (0.01–0.15 Hz) band, slow-4 (0.027–0.073 Hz) and slow-5 (0.01–0.027 Hz) bands. In addition, the fractional anisotropy (FA) values in WM in 23 patients and 26 HCs were examined using tract-based spatial statistics (TBSS) and tractography based on diffusion tensor imaging (DTI). Pearson correlation analysis was applied to analyze the relationships between ALFF values and Hamilton Depression Scale (HAMD) and Hamilton Anxiety Scale (HAMA).ResultsCompared with the HCs, MDD patients showed decreased ALFF values in posterior thalamic radiation (PTR) and superior longitudinal fasciculus (SLF) in slow-5 frequency band, no significant differences of ALFF values were found in typical and slow-4 frequency bands. In addition, there were no significant differences in FA values with TBSS analysis as well as the number of fibers in PTR and SLF with tractography analysis between two groups. Further correlation analysis showed that the ALFF value in SLF was negatively correlated with HAMA-2 score (r = −0.548, pFDR = 0.037) in patients.ConclusionOur results indicated that WM dysfunction may be associated with the pathophysiological mechanism of depression. Our study also suggested that the functional damage of the WM may precedes the structural damage in first-episode MDD patients. Furthermore, for mental disorders, slow-5 frequency band may be a more sensitive functional indicator for early detection of abnormal spontaneous brain activity in WM.

Whole-brain, gray, and white matter time-locked functional signal changes with simple tasks and model-free analysis

“…However, multiple reports have demonstrated successful detection and analysis of BOLD signals in white matter ( 11 , 12 ). For example, previous studies have reported white matter BOLD signal responses to tasks and at rest ( 13 – 16 ), relationships between white matter signals and the gray matter regions to which they connect ( 17 – 19 ), alterations of white matter BOLD signal in disease/disorder ( 20 – 25 ), and finally, robust, reproducible network properties of white matter BOLD signals ( 18 , 26 ). Importantly, recent reports have confirmed that white matter responses to stimuli are similar to, but different from, those in gray matter ( 13 , 14 , 27 , 28 ), generally indicating a slower response, smaller percent signal change, and variation across regions ( 29 ).…”