A Resting-state FMRI Study Of Brain Functional Connectivity Changes In High Myopia

Objective: High myopia is defined as a spherical ?-6.00 diopters, it is also called pathological myopia. Although with a corrected visual acuity, the visual function, such as visual field and contrast sensitivity, is abnormal in high myopia with respect to emmetropics. Previous studies have observed that long-term high myopia can lead to brain structural changes and even abnormal visual attention. Nevertheless, there is little study about the effect of high myopia on brain neural activity. The present study aims to investigate the influence of long-period abnormal visual experience on resting-state brain functional connectivity in the high myopia and to provide an experimental basis to understand the impact and neural mechanism of abnormal visual experience on the brain function.Materials and methods: Fifty-nine right-handed students from Tianjin Medical University were recruited for the study and 27 of them were high myopia(age: 21-25 years, 5 males) with a spherical ?-6.00 diopters. The onset age of myopia was no less than 9 years old. The remaining 32 were emmetropics taken as normal controls(age: 18-25 years, 14 males). There was no significant difference in age or education level between the high myopia and normal controls groups, whereas uncorrected visual acuity of the two eyes showed significant group difference. Resting-state functional magnetic resonance imaging(f MRI) data and 3D W1 TI structural images were obtained from all participants.For the resting-state f MRI data, data-driven method of functional connectivity density mapping(FCDM) was used to investigate difference of short- and long-range FCD between the high myopia and normal controls. A correlation analysis was performed between FCD in regions showing significant group difference and the uncorrected visual acuity of high myopia. Moreover, seed-based functional connectivity analysis was used to investigate the group difference of functional connectivity between regions of interest(ROI) that showing long-range FCD alterations. Based on these results, brain network functional connectivity analysis was further performed. For the 3D W1 TI structural images, group difference of gray matter volume was explored on basis of regions showing FCD alterations between the high myopia and normal controls.Results: The high myopia group showed decreased short-range FCD in bilateral posterior cingulate cortex/precuneus(PCC/pre Cun). Meanwhile, reduced long-range FCD was observed in right PCC/pre Cun, left inferior temporal gyrus(ITG), right supramarginal gyrus(SMG) and right rostrolateral prefrontal cortex(rl PFC) in the high myopia. The long-range FCD of the right rl PFC displayed a significantly positive correlation with the uncorrected visual acuity of high myopia. ROI-based functional connectivity analysis demonstrated that the high myopia group showed decreased functional connectivity not only between the right SMG and rl PFC, but also between the ventral attention network, which the SMG belongs to, and the frontoparietal control network, which the rl PFC belongs to. Additionally, the high myopia showed significantly reduced gray matter volume in the rl PFC.Conclusions: 1. The decreased short- and long-range FCD in the PCC/pre Cun indicates that the function of PCC/pre Cun for controlling efficient allocation of spatial attention may be abnormal in high myopia.2. The decreased long-range FCD in the ITG, which locates in the ventral visual pathway and involves in controlling for visual attention, may indicate that the function of ITG for attentional modulation is abnormal in high myopia.3. The high myopia showed reduced functional connectivity not only between the SMG and rl PFC, but also between the ventral attention network, which the SMG belongs to, and the frontoparietal control network, which the rl PFC belongs to. It suggests a reduced ability of frontoparietal control network in modulating the attention network.4. The reduced gray matter volume in the rl PFC may suggest that high myopia can cause not only the brain functional changes, but also the brain structural changes.