Magnetic Resonance Imaging Based Brain Network Construction And Its Application Research

A sophisticated and highly organized system,the human brain is capable of processing multiple tasks with high efficiency.The interconnected regions of the brain delineate the operation patterns of integration and segregation,which indicates the ability to rapidly organize specialized information from distributed brain regions in a functional manner.Therefore,brain connectome has been widely applied in research on brain mechanisms and psychiatric disorders.Extraction of regional morphometric features is one of the major steps in constructing a morphological brain network.Individual brain atlas statistical parametric mapping(IBASPM)is a toolbox that involves a fully automated stream for realizing the individualization of brain atlas,individual atlas-based segmentation,and measurement of regional gray matter volume in the subjects' native space by implementing an inverse deformation field.So far,this morphometric feature has never been applied to build morphological brain networks.Furthermore,despite the remarkable progress of studies on morphological connectomes in recent years,such research mainly focuses on the population-based similarity of morphometric structures.Although several novel approaches have been developed to extract structural information directly from T1-weighted MR images and obtain interregional connectivity for a single subject,most previous studies have built their morphological networks by using only one morphometric feature mathematically.Hence,we first extended previous studies by proposing novel ideas for realizing the formation of individual morphological brain networks and applied it to the research of early-stage Alzheimer's disease(AD).Additionally,episodic memory is the memory of autobiographical events,related to the times and places.Previous studies have documented that episodic memory exhibits both rapid improvement in the developing brain and fast decline in the aging brain,making it one of the most dynamically changing functions across the lifespan.However,there is no study heretofore conducted to explore the life-long changes of episodic memory.Hence,this dissertation focused on the above scientific topics,trying to develop novel methods of morphological brain network construction and applying multi-modality brain networks to explore brain mechanism and psychiatric disorders.The key research components including:1.By constructing morphological brain networks based on the regional gray matter volume extracted via IBASPM for both young and aging groups,this study endeavors to explore further alterations in normal aging.We found the reduced volumetry of the aging group mainly localized in the orbitofrontal cortex,lateral temporal cortex,and cingulate cortex.In stark contrast with the brains of the young group,increased positive connection strength was primarily identified within the aging patients' frontal lobe.Moreover,the spatial distribution of global hubs in the aging group manifests right lateralization.These new findings suggest the feasibility of using IBASPM-extracted volume measurements to build a morphological network,which could provide valuable supplementary information.2.Taking advantage of the fact that multiple morphometric features can be extracted from a single brain region,the interregional morphological connections were computed as the correlation of feature vectors instead of as one feature,and each of these vectors comprised nine complementary morphometric features.Small-worldness was observed in all the subjects,as well network robustness.The results indicate that the multiple morphometric features can be applied to form a rational and reproducible individual-based morphological brain network.3.By using the above-mentioned individual morphological brain network,this study attempts to explore the connective anomalies in the early stage of AD.AD is one of the most common forms of dementia that gradually and adversely impacts memory and cognition.As the influence of AD differs among patients,using individual morphological brain networks to investigate the relationship between cognitive functions and brain network structures would provide the most accurate results.The findings show that the significantly affected connections were observed across multiple regions,primarily related to the left entorhinal cortex.In addition,profound correlation was noted of the cognitive functioning score and global efficiency in the AD patients,which indicates the potential role of graphics properties in the determination of early-stage AD patients.Overall,the findings further confirm the selective AD-related disruptions in morphological brain networks and also suggest the feasibility of applying the morphological graphics properties in the discrimination of early-stage AD patients.4.Based on the resting-state functional MRI scans of the infants(neonates,one-year-olds and two-year-olds)together with young adults and aging subjects were studied to characterize the life-long development of hippo-cortical functional connectivity,so as to systematically describe the changes pattern of episodic memory.The hippocampus is central to memory,particularly episodic memory.Our results revealed fast synchronization during infancy,dramatic specialization between two years of age and young adulthood,and marked decline during aging.Compared with higher-order and primary functional systems,changes within the HDMS were the most dramatic across all three stages examined(i.e.,during infancy,between infancy and adulthood,and after adulthood).Our delineation of the lifespan HDMS functional connectivity growth trajectories provides a potential neural basis for the observed development of episodic memory.For instance,the mechanism of infantile amnesia may be related to the reorganization of connectivity during childhood.Our findings suggest that hippocampus-dependent functional connectivity measures may have the potential to serve as candidate objective biomarkers to help design effective interventions to either promote better memory development during early childhood,or to slow down memory decline during the aging process.