Resting - state functional MR changes in Alzheimer's disease patients visualized by amplitude of low - frequency fluctuation and fraction of amplitude of low - frequency fluctuation

Abstract

Objective To investigate the difference of amplitude of low-frequency fluctuation (ALFF) and fraction of amplitude of low-frequency fluctuation (f ALFF) between Alzheimer's disease (AD) patients and normal aging (NA) controls by voxel-based analysis. Methods Thirty-one AD patients and 44 NA controls were enrolled in the study.Blood oxygen level dependent functional (BOLD) EPI data were obtained during resting-state by using 32-channel head coil.Data were realigned,normalized and then smoothed with 8 mm FWHM kernel.Resting-state f MRI toolkit (version 1.6) was used to generate ALFF and f ALFF images.Independent two sample t-test was performed with SPM5 to compare ALFF and f ALFF of AD and NA controls.Pearsoncorrelation analysis was performed to examine the relationship between MMSE score and ALFF,f ALFF parameters.The significance level was set to be uncorrected 0.001 on the voxel level and 0.05 on the cluster level. Results AD patients showed increased ALFF in left temporal lobe (0.492±0.119) and right cingulated cortex (0.434±0.093) of AD patients,which were 0.443±0.068 and 0.380±0.081 in NA controls (t=2.658,2.227,P<0.05).Decreased f ALFF was found in bilateral posterior cingulate cortices (1.167±0.203) and increased f ALFF was found in bilateral temporal lobes (left 1.226±0.127,right 1.146±0.214) with left side dominance,which were 1.453±0.269,1.134±0.088,1.014±0.132 in NA controls (t=5.001,3.695,3.285,P<0.05).Bilateral temporal ALFF and f ALFF correlated with MMSE positively (r=0.768—0.909,P<0.05) with left dominance. Conclusion AD patients showed increased resting-state functional MRI changes correlated with MMSE scorein the temporal lobes with left dominance,which indicated left temporal lobe may be the best location for the observation of disease progression in AD patients. Key words: Alzheimer disease; Magnetic resonance imaging