To explore the features of resting state functional magnetic resonance imaging (rs-fMRI) in the patients with mild cognitive impairment (MCI) after during the process of converting to Alzheimer's disease (AD) dementia. To study the correlation of the brain function imaging and neuropsychological scores in converted MCI subjects with the purpose of finding the potential functional biomarkers which may predict the conversion of MCI to AD dementia in short term using resting state functional MRI.

Twenty-seven patients with MCI and 31 age, gender and years of education matched normal controls (NC) were enrolled in this study and neuropsychological assessment and rs-fMRI data were acquired respectively at the baseline and follow-up. Functional connectivity strength (FCS) analyses were used to assess the functional differences among the groups of MCI-converters (MCI-c), MCI-non converters (MCI-nc) and NC. Variance analyses were used to compare the group differences in age, years of education and each neuropsychological assessment. In addition, Chi-squared test was used to compare group differences in gender. Then, Kruskal-Wallis test was used to compare group differences in the interval time of twice data collection. Group differences in FCS values were analyzed by general linear model. Finally, correlation analyses were used to evaluate the relationships between the FCS values of the brain regions with group differences and neuropsychological assessment scores in MCI patients.

(1) Significant group differences of FCS among the MCI-c, MCI-nc and NC groups were observed in bilateral angular gyri, bilateral orbitofrontal cortex, right precentral gyrus, left paracentral lobule, left precuneus, right fusiform, right middle occipital gyrus, right superior occipital gyrus, left cerebellum. (2) The MCI-c showed decreased FCS in bilateral angular gyri, right middle occipital gyrus, right superior occipital gyrus, right inferior occipital gyrus, right fusiform, left precuneus, and left paracentral lobule, as compared to MCI-nc, the cluster was 149, 114, 186, 56, 48, 33, 38 and 102 voxels, respectively;P<0.05, respectively. The correlation analysis showed that the FCS values of the right angular gyrus were negative correlated with the MMSE scores (r=-0.561, P=0.017).

This study revealed that the comparison of rs-fMRI imaging data between MCI-c and MCI-nc at baseline is of great benefits in analysing the imaging characteristics of patients during converting from MCI to AD. The feature of FCS in rs-fMRI in right angular gyrus might serve as early indicators for the dysfunction and progression from MCI to AD.

Mild cognitive impairment; Alzheimer's disease; Magnetic resonance imaging; Conversion