Amplitude of low-frequency fluctuation and functional connectivity analysis based resting-state functional magnetic resonance imaging study in bipolar II depression patients

Abstract

Objective To examine the characteristics of spontaneous activity of brain regions in bipolar Ⅱ depression patients by using resting state fMRI technology, and explore the pathogenesis of bipolar Ⅱ depression. Methods In total 21 bipolar Ⅱ depression patients (BD group) and 21 gender-, age- and education-matched healthy controls (HC group) were recruited. The patients were diagnosed according to the DSM-Ⅳ criteria, and the symptoms were evaluated by the Montgomery-Asberg Depression Rating Scale (MADRS), HAMD17 and HAMA. The resting-state data was collected via a 3.0 T GE MRI, and was analyzed using an amplitude of low-frequency fluctuation (ALFF) approach, and two-samples t test was used to analyze the difference between BD group and HC group. Correlation analysis was used between the mean value of ALFF in brain regions which were significantly different from the other regions and the depression severity. The brain areas that were significantly different from the other brain regions were regarded as regions of interest, and were made functional connectivity with the whole brain. The functional connectivity was compared between the two groups to explore the impaired emotional network in bipolar Ⅱ depression. Results The ALFFs of left paracentral lobule(t=3.80), right precuneus (t=3.54) and right precentral gyrus(t=3.66) in BD group were significantly higher than HC group (all P<0.05, GRF correction) . In BD group, the ALFFs of the left orbital frontal gyrus (r=0.75) and right orbital frontal gyrus (r=0.80) were positively correlated with the HAMA score. The ALFFs of bilateral gyri rectus (r=0.73) and brain regions near the left insular lobe (r=0.74) were positively correlated with the HAMD17 score. The ALFF of region 2 of right cerebellar peduncles (r=-0.65) was negatively correlated with the MADRS score (all P<0.05) . The functional connectivity between paracentral lobule, precuneus, precentral gyrus and left middle frontal gyrus, left anterior cingulate gyrus together with its lateral gyrus in BD group was significantly increased relative to HC group (t=4.47, 4.07; both P<0.05), while the functional connectivity between the right rectangular shape crack and the cortex around was decreased in BD group (t=4.54, P<0.05). Conclusion In bipolar Ⅱ depression patients, the brain function of left paracentral lobule, right precuneus and right precentral gyrus may be impaired and correlated with severity of depressive. Key words: Bipolar disorder; Magnetic resonance imaging; Resting state; Amplitude of low-frequency fluctuation; Functional connectivity