Multimodal MRI Analysis Of Visual Deprivation Effects On Human Brain Structural And Functional Networks

Objective: This study aims to investigate changes in cortical structure,fiber connectivity,and functional networks in totally blind patients following complete loss of vision using multimodal magnetic resonance imaging techniques,and seeks to analyze the correlation between the duration of blindness and these changes.Based on that,the study categorizes blind subjects into early-onset and late-onset blindness groups according to the age of onset,with attempts to study differences in cortical structure,fiber connections,and functional networks between these groups.The insights gained from this research offer a more extensive understanding of how total blindness impacts brain structure and function,making it an essential building block for future research on visual cortical prosthetics.Methods: 34 totally blind patients who met the selection criteria were recruited,along with 25 healthy volunteers who were matched for gender,age,and educational level.In order to avoid bias,all participants were screened with the MMSE and Mo CA scales to ensure comparable mental,intellectual,and cognitive baselines.A 3.0T MRI scanner was used for whole-brain scanning to obtain structural images,diffusion tensor imaging(DTI),and resting-state BOLD f MRI raw data.Softwares including SPM12,CAT12,FSL,and GRETNA were used to preprocess and postprocess the structural images,DTI,and BOLD f MRI data.From these,cortical structural parameters,fiber indices based on TBSS,functional modular connection data,and network attribute indices based on graph theory for the blind and control groups were obtained.The indices data for the blind and control groups were analyzed for differences using a two-sample T-test.The differences obtained were further analyzed for correlations with the duration of blindness using multiple linear regression.Within the blind group,subjects were divided into early-onset and late-onset blindness groups based on the age of onset,and a two-sample T-test was used to analyze differences in cortical structure indices,fiber indices,functional connections,and functional network attributes between the two groups.Results: 1.The primary changes in cortical structure between the blind individuals and the healthy control group were found in the bilateral pericalcarine cortex,right lingual gyrus,posterior part of the left middle frontal gyrus,and the left superior parietal gyrus.Alterations in fiber connections of the fibers primarily involved in visual information processing were observed in;the bilateral superior and inferior longitudinal fasciculus,inferior fronto-occipital fasciculus,anterior thalamic radiation,and the forceps major of the corpus callosum.Changes in functional connectivity included a decrease in the connection strength within the visual module,a weakened connection between the visual and hand-body motor modules,and an enhanced connection between the visual and frontoparietal modules.In terms of network node attributes,multiple brain region node attributes within the visual network of blind individuals were diminished,whereas certain brain region node attributes within the Default Mode Network(DMN)and Ventral Attention Network(VAN)were enhanced.2.The cortical parameter that showed a linear correlation with the duration of blindness was the gyrification index of the left superior parietal gyrus,it was positively correlated;The fiber parameter that showed a linear correlation was the Radial Diffusivity(RD)value,with the correlated fibers including the bilateral inferior longitudinal fasciculus,inferior fronto-occipital fasciculus,and the forceps major of the corpus callosum,all showing positive correlations;The inter-modular connection strength showing a correlation was between the visual and hand-body motor modules,exhibiting a negative correlation;The network node attribute correlations included a positive correlation with the degree centrality of Region 75 within the DMN and a positive correlation with the local node efficiency of Region 235 within the VAN.3.The primary differences in cortical parameters between the early-onset and late-onset blindness groups were located in the bilateral orbital frontal cortex and the left fusiform gyrus.The main differences in fiber parameters involved fibers associated with visuospatial language processing,including the left superior and inferior longitudinal fasciculus,and the left inferior fronto-occipital fasciculus.The conduction functions of these fibers were diminished in the early-onset blindness group compared to the late-onset group.Differences in network node attributes included enhanced attributes in certain brain regions of the Default Mode Network(DMN)and Salience Network(SN)in the early-onset blindness group compared to the late-onset group.Simultaneously,the node attributes of region 172 within the visual network were enhanced in the early-onset blindness group compared to the late-onset group.Conclusion: The primary impacts of visual loss on the brain structure and functional networks of blind individuals are alterations in the cortex,fiber connections,and network attributes related to visual function,with some of these changes correlating with the duration of blindness.Meanwhile,due to the loss of this crucial sensory function,other functional networks including the DMN,Ventral Attention Network(VAN),and Attention Network(AN)undergo compensatory changes,leading to functional network reorganization.As early-onset blindness occurs before the brain has completely integrated various developmental sensory information,functional reorganization is more apparent in early-onset blindness patients compared to late-onset patients.Moreover,degeneration of fibers related to visuospatial language is more evident in early-onset blindness patients.In addition,due to more pronounced changes in the DMN and AN functional networks in early-onset blindness patients,their risk of developing mental disorders may be higher and should be closely monitored.