Functional Connectivity Of Thalamo-cortical Pathway And Brain Functional Network Analysis In Primary Angle-closure Glaucoma By Using Resting State FMRI

Objective: To improve the understanding of the potential neural mechanism and help for early clinical diagnosis and treatment in patients with primary angle-closure glaucoma?PACG?,we aimed to investigate the alterations of functional connectivity of thalamo-cortical pathway and brain functional network by using voxel-wise functional connectivity?FC?and graphy theory analysis in resting state fMRI.Methods: 33 patients with PACG?PACG group?and 33 age-and gender-matched healthy controls?healthy controls,HC group?were recruited in our study,all the PACG patients were performed by ophthalmic testing,including intraocular pressure?IOP?,retinal nerve fiber layer?RNFL?,cup to disc ratio?CDR?and visual activity?VA?.All of the subjects underwent SIEMENS Trio Tim 3.0T MR scan to get resting-state functional MRI?RS-fMRI?data.Data analysis include:?1?Isolating bold data,?2?Data preprocessing by using DPARSFA software;?3?Parceling the bilateral thalamus into each 7 region of interest?ROI?and using those ROIs to make a functional connectivity analysis with the whole brain voxel,then using independent two-sample t-test to analyze differences between the two groups?AlphaSim correction,P < 0.01?;?4?Using Gretna software,the 116 Automated Anatomical Labeling?AAL?template regions were parcellated into the brain network nodes,functional connectivity was applied to calculate the Pearson coefficient.The global and regional properties were computed by graph theoretical analysis,and the brain network topological differences in regional properties between the two groups were compared by two-sample t-test?false discovery rate correction,FDR,P<0.05?;?5?Analysizing the correlation coefficient and network properties values of changed brain regions,and the relationships between those values and clinical parameters were further examined by SPSS V.17.0.Results:?1?Compared with HC group,decreased FC was found along the thalamic ROIs-visual pathways?parietal lobe/precuneus,frontal lobe/inferior frontal gyrus?and nonvisual pathways?paracentral lobule,postcentral gyru,limbic lobe/hippocampus?of PACG,and increased FC in thalamic ROIs-visual pathways?occipital lobe,parietal lobe/inferior parietal lobe,temporal lobe/inferior temporal gyrus?and nonvisual pathways?anterior lobe of cerebellum/cuneus??P < 0.01,AlphaSim correction,clusters? 29?.?2?Over the sparsity range?0.1⁰.6?,both the networks of PACG and HC group exhibited efficient small-world characteristics,and normalized clustering coefficient????1,normalized characteristic path length????1,small-wordness????1.?3?Over the minimum and maximum sparsity range?0.32⁰.42?,compared with the HC group,the functional brain networks in PACG showed a slightly lower ??P: 0.283⁰.453?,and a no changed ??P: 0.463⁰.993?,resulting in a slightly lower ??P: 0.322⁰.548?,however,the alterations of those differences were found to be not statistically significant changed?P>0.05,FDR correction?.The global(E_global)and local(E_local)efficiency were also found no significant changed?P>0.05,FDR correction?.?4?In the minimum sparsity range of 0.32,compared with the HC group,decreased normalized degree in the primary and secondary visual cortex?bilateral calcarine,left superior occipital gyrus,right inferior occipital gyrus,bilateral cuneus?,whereas increased normalized degree in the dorsal visual pathway brain regions?right thalamus,bilateral middle temporal gyrus?,and nonvisual pathway brain regions?bilateral supplementary motor area,right parahippocampal,right paracentral lobule,right inferior frontal?opercular part??were found in PACG?P<0.05,FDR correction?.Decreased normalized node betweenness in dorsal visual pathway brain regions?left superior/inferior occipital gyrus,bilateral cuneus,left lingual gyrus?,and nonvisual pathway brain regions?left superior frontal gyrus,left superior/middle frontal gyrus?orbital part?,left hippocampus,left putamen,left cerebelum,and vermis?;meanwhile,increased normalized node betweenness in the dorsal/ventral visual pathway regions?right middle temporal gyrus,right middle temporal pole,left inferior temporal gyrus?,and nonvisual pathway regions?right parahippocampal,right paracentral lobule,bilateral inferior frontal gyrus?opercular part?,bilateral supramarginal gyrus?were found in PACG patients?P<0.05,FDR correction?.?5?In the sparsity range of 0.32,positive correlation was found between the left middle frontal gyrus?orbital part?of normalized node betweenness and vertical CDR?r=0.406,P=0.019?,and between the left supramarginal gyrus?r=0.357,P=0.041?,right supramarginal gyrus?r=0.558,P=0.001?and left putamen?r=0.355,P=0.043?of normalized node betweenness and visual activity?VA?.The negative correlation was found between the right cuneus of normalized degree and VA?r=-0.371,P=0.034?.The other brain regions values of correlation coefficient and network properties?noamalized node betweenness and degree?were found no significant correlation with RNFLT,CDR,IOP and VA.Conclusions:?1?The abnormalities in FC of thalamic ROIs within and outside visual pathways?somatomotor and emotion-cognition?in PACG group,which had an effection on visual related cognitive function of PACG;?2?PACG group exhibited efficient small-world characteristics,tending to a homogenization brain global construction.?3?The visual and nonvisual?somatomotor?brain regions were changed in PACG group,including default mode network?DMN?,which may be one of the mechanisms of abnormal psychological activities in PACG patients.?4?The visual brain regions of PACG had a correlation with VA,and nonvisual brain regions had an correlation with CDR and VA.