Functional brain activity in patients with amnestic mild cognitive impairment: an rs-fMRI study

Abstract

Background: Amnestic mild cognitive impairment (aMCI) is an early stage of Alzheimer's disease (AD). Regional homogeneity (ReHo) and amplitude of low-frequency fluctuation (ALFF) are employed to explore spontaneous brain function in patients with aMCI. This study applied ALFF and ReHo indicators to analyze the neural mechanism of aMCI by resting-state functional magnetic resonance imaging (rs-fMRI).

Methods: Twenty-six patients with aMCI were included and assigned to the aMCI group. The other 26 healthy subjects were included as a healthy control (HC) group. Rs-fMRI was performed for all participants in both groups. Between-group comparisons of demographic data and neuropsychological scores were analyzed using SPSS 25.0. Functional imaging data were analyzed using DPARSF and SPM12 software based on MATLAB 2017a. Gender, age, and years of education were used as covariates to obtain ALFF and ReHo indices.

Results: Compared with HC group, ALFF decreased in the left fusiform gyrus, left superior temporal gyrus, and increased in the left cerebellum 8, left inferior temporal gyrus, left superior frontal gyrus (BA11), and right inferior temporal gyrus (BA20) in the aMCI group (p < 0.05, FWE correction). In addition, ReHo decreased in the right middle temporal gyrus and right anterior cuneiform lobe, while it increased in the left middle temporal gyrus, left inferior temporal gyrus, cerebellar vermis, right parahippocampal gyrus, left caudate nucleus, right thalamus, and left superior frontal gyrus (BA6) (p < 0.05, FWE correction). In the aMCI group, the ALFF of the left superior frontal gyrus was negatively correlated with Montreal Cognitive Assessment (MoCA) score (r = -0.437, p = 0.026), and the ALFF of the left superior temporal gyrus was positively correlated with the MoCA score (r = 0.550, p = 0.004). The ReHo of the right hippocampus was negatively correlated with the Mini-Mental State Examination (MMSE) score (r = -0.434, p = 0.027), and the ReHo of the right middle temporal gyrus was positively correlated with MMSE score (r = 0.392, p = 0.048).

Conclusion: Functional changes in multiple brain regions rather than in a single brain region have been observed in patients with aMCI. The abnormal activity of multiple specific brain regions may be a manifestation of impaired central function in patients with aMCI.

Keywords: amnestic mild cognitive impairment; amplitude of low-frequency fluctuation; imaging marker; regional homogeneity; resting-state functional magnetic resonance imaging.

Figure 1

(A) Comparison of MMSE scores between two groups (*p < 0.001). (B) Comparison of MOCA scores between two groups (*p < 0.001).

Figure 2

Brain area maps of ALFF changes in brain regions of the aMCI group compared to HC group. (A) Axial map, (B) Sagittal map, (C) Coronal map, (D) 3D map, ALFF = amplitude of low- frequency fluctuations.

Figure 3

Brain area maps of ReHo changes in the brain regions of the aMCI group compared to HC group. (A) Axial map, (B) Sagittal map, (C) Coronal map, (D) 3D map, ReHo regional homogeneity.

Figure 4

Correlation between the functional index data of brain regions and the neuropsychological scale scores. (A) Correlation analysis between Frontal_Sup_Orb_LALFF values and MoCA scores, (B) Correlation analysis between Temporal_Pole_Sup_L ALFF values and MoCA scores, (C) Correlation analysis between ParaHippocampal R ReHo values and MMSE scores, (D) Correlation analysis between Temporal_Mid_R ReHo values and MMSE scores.