Early neuroimaging features of subthreshold depression: Abnormalities in frontoparietal white matter microstructure and functional activity.

Subthreshold depression (StD) is a prevalent mood disorder, and may be at higher risk of depression. Although previous neuroimaging studies have investigated brain abnormalities in StD, the changes of structure and functional activities in the frontoparietal network (FPN) remain far from be elucidated. In the present study, we aimed to investigate structural and functional activity changes in FPN among young individuals with StD, utilizing diffusion tensor imaging (DTI) and functional magnetic resonance imaging(fMRI). Tract-based spatial statistic analysis revealed that individuals with StD had decreased fractional anisotropy (FA) within the bilateral body and genu of the corpus callosum. Additionally, tractography analysis indicated a significant reduction in white matter fiber in the middle cingulum and left paracentral lobule in individuals with StD. The functional connectivity (FC) was significantly decreased between the medial and paracortical cingulate gyrus - medial superior frontal gyrus, the anterior cingulate and paracortical cingulate gyrus - precuneus, and the medial superior frontal gyrus - dorsal superior frontal gyrus in individuals with StD. Furthermore, a significant negative correlation was observed between FC and the Center for Epidemiologic Studies Depression (CESD) scores in the medial superior frontal gyrus - dorsal superior frontal gyrus. Besides, the regional homogeneity in the precuneus was significantly increased and positively correlated with CESD scores. The betweenness centrality in the medial superior frontal gyrus was significantly decreased. In summary, the present study demonstrated FPN structural and functional abnormalities associated with StD, which may offer valuable insight for future clinical research of StD.