Amplitude of low-frequency fluctuation in major depressive patients with hypomanic symptoms: a fMRI study in resting-state

Abstract

Objective To investigate the characteristics of hypomanic symptoms (HS) to the brain neural activity in the resting-state of the patients with major depressive disorder (MDD). Methods Twenty-three patients from 54 patients with MDD were defined as MDD with HS because their HCL-32 scores were higher than or equal to 12. The rest 31 patients were defined as MDD patients without HS because of the lower scores. After checking the match of the factors such as gender and age et al, there were 19 MDD patients with HS, 19 patients without HS and 19 healthy controls in the final analysis. We analyzed the impact of HS to the regional brain function of the patients with MDD by amplitude of low-frequency fluctuation (ALFF). Results The patients with MDD had abnormal resting-state brain activity in a diffuse brain areas compared to healthy controls by the ALFF analysis. Compared to the patients without HS, the ALFF of the depressed MDD patients with HS were significantly higher in the bilateral orbitofrontal cortex (OFC; left OFC: MNI(x,y,z): - 34,56,- 10; t=5.26; right OFC: MNI(x,y,z): 20, 66, - 2; t=493) and superior frontal cortex (SFC; left SFC: MNI(x,y,z): -4, 66, 8; t=4.12; right SFC: MNI(x,y,z): 14, 56, 18, t=3.97, all P< 0.05); while lower in bilateral thalamus and left fusiform gyrus (P<0.05). Correlation analysis of ALFF at each voxel in the whole brain against the HCL-32 in the patients with MDD revealed significantly positive correlation in OFC (r=0.363, 0.426, 0.405, all P<0.05), negative correlation in left thalamus and left fusiform gyrus (r=- 0.352, P<0.05; r=- 0.468, P<0.01). Conclusions The study suggested that there were differences between the two subgroups patients with MDD defined by the HCL-32. Compared to the MDD without HS patients, MDD with HS patients showed increase ALFF in bilateral frontal cortex (especially the OFC), and decrease ALFF in left thalamus and left fusiform gyrus. These features may be regarded as the biomarker of the MDD patients who were positive to HCL-32 screening. Key words: Major depressive disorder; Hypomanic symptoms; Resting state; Functional magnetic resonance imaging; Amplitude of low-frequency fluctuation