Altered regional homogeneity of brain spontaneous signals in SIV infected rhesus macaque model.

BACKGROUND: Regional homogeneity (ReHo), a measurement from resting-state functional magnetic imaging (rs-fMRI) to reflect local synchronization of brain activities, has been widely explored in previous studies of neurological diseases. SIV infected model for detecting the neurological changes with progression was studied.

METHODS: In the study, six rhesus macaques infected by simian immunodeficiency virus (SIV) were scanned by resting-state fMRI at the following time points: before SIV inoculation (baseline), 12weeks and 24weeks post inoculation (12wpi, 24wpi). Meanwhile, the immunological parameters including serum percentage of CD4+ T cell, CD4/CD8 ratio and absolute CD4+ T cell number were measured and analyzed.

RESULTS: In comparison of baseline, significant decreased ReHo was found in the left superior frontal gyrus, left superior temporal gyrus, left hippocampus, right precuneus, left angular gyrus, and bilateral occipital gyrus; in contrast increased ReHo in putamen at 12wpi. Moreover, at the time of 24wpi, decreased ReHo was observed in the right postcentral gyrus, left precentral gyrus, posterior cingulated gyrus and thalamus, while ReHo was increased in the left putamen, hippocampus, left anterior cingulated cortex and precentral cortex. The correlation analysis revealed that ReHo in the superior frontal gyrus showed negative association with CD4/CD8 ratio and positive with absolute CD4+ T cell number. The correlation analysis showed that percentage of CD4+ was correlated with the ReHo values in right middle frontal gyrus, bilateral thalamus and amygdala positively; negative relationship with left putamen, left superior frontal gyrus, left superior and middle temporal gyrus.

CONCLUSION: The study first indicates that hippocampus, putamen, frontal and occipital lobe were impaired by using rs-fMRI and correlated with immunological parameters. Thus, ReHo value can be utilized as a noninvasive biomarker of spontaneous brain activity changes caused by the progression of neurological impairments.