Interhemispheric functional connectivity in primary insomnia: a resting-state functional MRI study

Objective: To investigate the resting-state functional connectivity between the two hemispheres in primary insomnia(PI) using voxel-mirrored homotopic connectivity(VMHC) based on resting-state functional MRI(fMRI). Methods: Eighteen PI patients and 19 healthy volunteers matched for age and sex underwent resting- state fMRI scans in a 1.5 T scanner. Pittsburgh sleep quality index(PSQI) was performed for all subjects. The data was pre-processed by SPM 8 and then the VMHC values were calculated by REST software. The VMHC values between the two groups were compared by two-sample t-test. The statistical map with significant differences of VMHC value was obtained. Results Compared to the controls, PI patients showed significant VMHC decreases in the middle frontal gyrus(MFG), superior frontal gyrus(SFG), orbitofrontal cortex(OFC), hippocampus, thalamus, insula and a few occipital regions including cuneus and lingual gyrus(voxel size 1269-7425 mm³, t = -4.47--2.74, P < 0.05, Alphasim corrected). Negative correlation was observed between VMHC coefficients(0.324 ± 0.247) of OFC and the PSQI score (10.1 ± 1.7) in PI patients(r = -0.69, P < 0.01). The other regions showing significant VMHC changes had no correlation with the PSQI score(P > 0.05). Conclusions: These findings suggest that the functional coordination between homotopic brain regions is impaired in PI patients. Interhemispheric RSFC may serve as a useful method for evaluating PI where neural connectivity is implicated in the pathophysiology. (authors)