Callosal Parcellation Mapping Based On Brain White Matter Netowrks And Its Application In Brain Connectivity Of Schizophrenia

Schizophrenia is one of the primary mental disorders in our modern society.Its etiology is not yet clear,while clinically abnormalities in emotion,attention,behavior,thinking and other aspects has been shown.So far,there are no effective prevention and treatment methods,and the disease often accompanies the patient for a lifetime.As the human brain's largest white matter(WM)fiber tissue,the corpus callosum is the key organization for the interhemispheric transfer of various primary and high-order cognitive information.Early studies have exhibited that patients with schizophrenia have thinner corpus callosum and exhibit abnormal functional activity during interhemispheric transmitting various primary and higher functional information tasks.Although the structural and functional abnormalities on corpus callosum have been investigated in schizophrenia,the underlying functional magnetic resonance imaging(fMRI)bloodoxygenation-level-dependent(BOLD)signals from corpus callosum and how the functional information was abnormally transferred between corpus callosum and other brain regions remains unclear.Blood oxygenation level dependent(BOLD)based fMRI signals can detect hemodynamic changes relating to intrinsic neural activity.Using fMRI signals,temporally synchronized brain activity can be assessed across local brain regions.However,most of these studies in fMRI have primarily focused on the gray-matter BOLD signals.The BOLD signals within WM have typically been considered to be noise dominated and rarely reported in neuroimaging literature.Recent studies confirm that WM BOLD signals can reflect the cerebral intrinsic neural and cannot simply be regarded as noise.This dissertation will provide new opportunities for understanding the interhemispheric transfer in schizophrenia.Adopting multimodal neuroimaging method,the dissertation will explore the intrinsic relationships between corpus callosum and WM functional networks(WM-FNs)from the novel WM functional imaging field and its application in schizophrenia.This dissertation is summarized into two parts and includes four main components.The first part of this dissertation,we will develop new methods and formulate theories to establish the functional and structural parcellation maps of corpus callosum closely related with distinct WM-FNs.Since BOLD signals within WM remains controversial,it will be a problem how to confirm that the unique connectivity pattern between corpus callosum and WM-FNs is caused by cerebral neural activity,rather than random physiological noise.To this end,combing with resting-state fMRI and diffusion tensor imaging(DTI)dataset,the study establishes the functional and structural parcellation maps of corpus callosum.In addition,we estimate the reproducibility of callosal parcellation map using other datasets.This part includes two main components as follows:Firstly,this dissertation establishes the functional parcellation map of corpus callosum corresponding to different WM-FNs.Using the K-means clustering approach,symmetric WM-FNs are obtained from the high-resolution fMRI dataset of human connectome project.Subsequently,the functional parcellation map of corpus callosum corresponding to different WM-FNs is obtained by performing the partial correlation and winner-take-all algorithms.The corpus callosum has a unique spatial distribution pattern relating to different WM-FNs.The different subregions of corpus callosum are associated with different primary and high-order functional systems in the human brain.This dissertation opens a new window for understanding the information communication from corpus callosum to whole-brain functional networks,which could help understand the neural substrates underlying normal interhemispheric functional connectivity as well as the dysfunctions in various mental disorders.Secondly,this dissertation establishes the structural parcellation map of corpus callosum corresponding to different WM-FNs.Combing resting-state fMRI and diffusion tensor imaging(DTI)dataset,this study extracts the fiber bundles connecting the WMFNs and corpus callosum,and further obtain a population-based callosal probabilistic parcellation map.These results show that the functional and structural parcellation maps have a good overlap,suggesting the existance of callosal parcellation map corresponding to different WM-FNs.Additionally,the correspondence of functional and structural parcellation maps suggests that BOLD signals within WM are not random noise,but can reflect the neural activity in the human brain.The second part of this dissertation investigates the abnormal interhemispheric information transfer in schizophrenia.The neural mechanism of hallucinations,delusions and cognitive impairment in schizophrenia has not been fully elucidated,and it is urgent to find new direction to fully describe brain-impaired mechanism of schizophrenia.This dissertation proposes to establish the abnormal connectivity pattern between corpus callosum and WM-FNs from a novel WM functional filed,which will reveal the neural mechanism of clinical manifestations in schizophrenia.This part includes two main components as follows:Firstly,adopting the voxel-mirrored homotopic connectivity method,this dissertation investigates the abnormal homotopic connectivity in schizophrenia,and then determines through which callosal subregions these fibers connecting to the bilateral abnormal regions pass.The results show the abnormally decreased homotopic connectivity in the bilateral middle occipital gyrus,corpus callosum,precentral gyrus and postcentral gyrus and abnormal structural connectivity in the corpus callosum and precentral gyrus,which provides the foundation for the subsequent study on the abnormal connectivity between corpus callosum and WM-FNs in schizophrenia.Secondly,adopting a multimodal neuroimaging approach,this dissertation analyzes the abnormal connectivity of callosal-WM-cortical circuit,and characterizes the internal relationships between abnormal connectivity and clinical manifestation of schizophrenia.These results exhibit the abnormal connectivity of callosal-WM-cortical circuit connecting to gray matter visual network,executive control network,ventral attention network,and default network.This dissertation reveals the abnormal interhemispheric information transfer of callosal-WM-cortical circuit,and provides important clues for understanding impairments in delusions,hallucinations,and cognitive impairment in schizophrenia.This dissertation establishes the parcellation map of corpus callosum corresponding to different WM-FNs from the new WM functional imaging field,forming a new method and theoretical foundation for exploring various mental disorders.Adopting above method and theories,this dissertation further investigates the abnormal functional and structural connectivity of callosal-WM-cortical circuit,which provides important clues for in-depth understanding the neuropathological mechanism of abnormal interhemispheric information transmission in schizophrenia.