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      Subsystem mechanisms of default mode network underlying white matter hyperintensity‐related cognitive impairment

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          Abstract

          Functional changes of default mode network (DMN) have been proven to be closely associated with white matter hyperintensity (WMH) related cognitive impairment (CI). However, subsystem mechanisms of DMN underlying WMH‐related CI remain unclear. The present study recruited WMH patients ( n = 206) with mild CI and normal cognition, as well as healthy controls (HC, n = 102). Static/dynamic functional connectivity (FC) of the DMN's three subsystems were calculated using resting‐state functional MRI. K‐means clustering analyses were performed to extract distinct dynamic connectivity states. Compared with the WMH‐NC group, the WMH‐MCI group displayed lower static FC within medial temporal lobe (MTL) and core subsystem, between core‐MTL subsystem, as well as between core and dorsal medial prefrontal cortex subsystem. All these static alterations were positively associated with information processing speed (IPS). Regarding dynamic FC, the WMH‐MCI group exhibited higher dynamic FC within MTL subsystem than the HC and WMH‐NC groups. Altered dynamic FC within MTL subsystem mediated the relationship between WMH and memory span (indirect effect: −0.2251, 95% confidence interval [−0.6295, −0.0267]). Additionally, dynamic FCs of DMN subsystems could be clustered into two recurring states. For dynamic FCs within MTL subsystem, WMH‐MCI subjects exhibited longer mean dwell time (MDT) and higher reoccurrence fraction (RF) in a sparsely connected state (State 2). Altered MDT and RF in State 2 were negatively associated with IPS. Taken together, these findings indicated static/dynamic FC of DMN subsystems can provide relevant information on cognitive decline from different aspects, which provides a comprehensive view of subsystem mechanisms of DMN underlying WMH‐related CI.

          Abstract

          • Static/dynamic FCs from DMN subsystems in WMH‐MCI subjects were significantly changed. These alterations helped facilitate the progression of WMH‐related CI.

          • Altered dynamic FC within MTL subsystem was shown to be a mediation framework between WMH and memory span.

          • Static and dynamic FC in DMN subsystems can provide relevant information on WMH‐related CI from different aspects.

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          The organization of the human cerebral cortex estimated by intrinsic functional connectivity.

          Information processing in the cerebral cortex involves interactions among distributed areas. Anatomical connectivity suggests that certain areas form local hierarchical relations such as within the visual system. Other connectivity patterns, particularly among association areas, suggest the presence of large-scale circuits without clear hierarchical relations. In this study the organization of networks in the human cerebrum was explored using resting-state functional connectivity MRI. Data from 1,000 subjects were registered using surface-based alignment. A clustering approach was employed to identify and replicate networks of functionally coupled regions across the cerebral cortex. The results revealed local networks confined to sensory and motor cortices as well as distributed networks of association regions. Within the sensory and motor cortices, functional connectivity followed topographic representations across adjacent areas. In association cortex, the connectivity patterns often showed abrupt transitions between network boundaries. Focused analyses were performed to better understand properties of network connectivity. A canonical sensory-motor pathway involving primary visual area, putative middle temporal area complex (MT+), lateral intraparietal area, and frontal eye field was analyzed to explore how interactions might arise within and between networks. Results showed that adjacent regions of the MT+ complex demonstrate differential connectivity consistent with a hierarchical pathway that spans networks. The functional connectivity of parietal and prefrontal association cortices was next explored. Distinct connectivity profiles of neighboring regions suggest they participate in distributed networks that, while showing evidence for interactions, are embedded within largely parallel, interdigitated circuits. We conclude by discussing the organization of these large-scale cerebral networks in relation to monkey anatomy and their potential evolutionary expansion in humans to support cognition.
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            Vascular contributions to cognitive impairment and dementia: a statement for healthcare professionals from the american heart association/american stroke association.

            This scientific statement provides an overview of the evidence on vascular contributions to cognitive impairment and dementia. Vascular contributions to cognitive impairment and dementia of later life are common. Definitions of vascular cognitive impairment (VCI), neuropathology, basic science and pathophysiological aspects, role of neuroimaging and vascular and other associated risk factors, and potential opportunities for prevention and treatment are reviewed. This statement serves as an overall guide for practitioners to gain a better understanding of VCI and dementia, prevention, and treatment. Writing group members were nominated by the writing group co-chairs on the basis of their previous work in relevant topic areas and were approved by the American Heart Association Stroke Council Scientific Statement Oversight Committee, the Council on Epidemiology and Prevention, and the Manuscript Oversight Committee. The writing group used systematic literature reviews (primarily covering publications from 1990 to May 1, 2010), previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and, when appropriate, formulate recommendations using standard American Heart Association criteria. All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. After peer review by the American Heart Association, as well as review by the Stroke Council leadership, Council on Epidemiology and Prevention Council, and Scientific Statements Oversight Committee, the statement was approved by the American Heart Association Science Advisory and Coordinating Committee. The construct of VCI has been introduced to capture the entire spectrum of cognitive disorders associated with all forms of cerebral vascular brain injury-not solely stroke-ranging from mild cognitive impairment through fully developed dementia. Dysfunction of the neurovascular unit and mechanisms regulating cerebral blood flow are likely to be important components of the pathophysiological processes underlying VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage of the brain, and VCI. The neuropathology of cognitive impairment in later life is often a mixture of Alzheimer disease and microvascular brain damage, which may overlap and synergize to heighten the risk of cognitive impairment. In this regard, magnetic resonance imaging and other neuroimaging techniques play an important role in the definition and detection of VCI and provide evidence that subcortical forms of VCI with white matter hyperintensities and small deep infarcts are common. In many cases, risk markers for VCI are the same as traditional risk factors for stroke. These risks may include but are not limited to atrial fibrillation, hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore, these same vascular risk factors may be risk markers for Alzheimer disease. Carotid intimal-medial thickness and arterial stiffness are emerging as markers of arterial aging and may serve as risk markers for VCI. Currently, no specific treatments for VCI have been approved by the US Food and Drug Administration. However, detection and control of the traditional risk factors for stroke and cardiovascular disease may be effective in the prevention of VCI, even in older people. Vascular contributions to cognitive impairment and dementia are important. Understanding of VCI has evolved substantially in recent years, based on preclinical, neuropathologic, neuroimaging, physiological, and epidemiological studies. Transdisciplinary, translational, and transactional approaches are recommended to further our understanding of this entity and to better characterize its neuropsychological profile. There is a need for prospective, quantitative, clinical-pathological-neuroimaging studies to improve knowledge of the pathological basis of neuroimaging change and the complex interplay between vascular and Alzheimer disease pathologies in the evolution of clinical VCI and Alzheimer disease. Long-term vascular risk marker interventional studies beginning as early as midlife may be required to prevent or postpone the onset of VCI and Alzheimer disease. Studies of intensive reduction of vascular risk factors in high-risk groups are another important avenue of research.
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              Tracking whole-brain connectivity dynamics in the resting state.

              Spontaneous fluctuations are a hallmark of recordings of neural signals, emergent over time scales spanning milliseconds and tens of minutes. However, investigations of intrinsic brain organization based on resting-state functional magnetic resonance imaging have largely not taken into account the presence and potential of temporal variability, as most current approaches to examine functional connectivity (FC) implicitly assume that relationships are constant throughout the length of the recording. In this work, we describe an approach to assess whole-brain FC dynamics based on spatial independent component analysis, sliding time window correlation, and k-means clustering of windowed correlation matrices. The method is applied to resting-state data from a large sample (n = 405) of young adults. Our analysis of FC variability highlights particularly flexible connections between regions in lateral parietal and cingulate cortex, and argues against a labeling scheme where such regions are treated as separate and antagonistic entities. Additionally, clustering analysis reveals unanticipated FC states that in part diverge strongly from stationary connectivity patterns and challenge current descriptions of interactions between large-scale networks. Temporal trends in the occurrence of different FC states motivate theories regarding their functional roles and relationships with vigilance/arousal. Overall, we suggest that the study of time-varying aspects of FC can unveil flexibility in the functional coordination between different neural systems, and that the exploitation of these dynamics in further investigations may improve our understanding of behavioral shifts and adaptive processes.
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                Author and article information

                Contributors
                xuyun20042001@aliyun.com
                Journal
                Hum Brain Mapp
                Hum Brain Mapp
                10.1002/(ISSN)1097-0193
                HBM
                Human Brain Mapping
                John Wiley & Sons, Inc. (Hoboken, USA )
                1065-9471
                1097-0193
                01 February 2023
                15 April 2023
                : 44
                : 6 ( doiID: 10.1002/hbm.v44.6 )
                : 2365-2379
                Affiliations
                [ 1 ] Department of Neurology Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University Nanjing China
                [ 2 ] Department of Neurology, Drum Tower Hospital, Medical School and The State Key Laboratory of Pharmaceutical Biotechnology, Institute of Brain Science Nanjing University Nanjing China
                [ 3 ] Department of Radiology Affiliated Drum Tower Hospital of Nanjing University Medical School Nanjing China
                [ 4 ] Jiangsu Key Laboratory for Molecular Medicine Medical School of Nanjing University Nanjing China
                [ 5 ] Jiangsu Province Stroke Center for Diagnosis and Therapy Nanjing China
                [ 6 ] Nanjing Neurology Clinic Medical Center Nanjing China
                Author notes
                [*] [* ] Correspondence

                Yun Xu, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 ZhongShan Road, Nanjing, Jiangsu 210008, China.

                Email: xuyun20042001@ 123456aliyun.com ;

                Author information
                https://orcid.org/0000-0002-8795-6122
                https://orcid.org/0000-0002-3953-0290
                Article
                HBM26215
                10.1002/hbm.26215
                10028636
                36722495
                53c1751b-ec9c-45d9-aec9-28e7d9cb3b04
                © 2023 The Authors. Human Brain Mapping published by Wiley Periodicals LLC.

                This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

                History
                : 09 January 2023
                : 07 December 2022
                : 10 January 2023
                Page count
                Figures: 7, Tables: 5, Pages: 15, Words: 11216
                Funding
                Funded by: Jiangsu Province Key Medical Discipline
                Award ID: ZDXKA2016020
                Funded by: Jiangsu Provincial Key Research and Development Program , doi 10.13039/501100013058;
                Award ID: BE2020620
                Funded by: National Natural Science Foundation of China , doi 10.13039/501100001809;
                Award ID: 81630028
                Award ID: 81920108017
                Funded by: National Key Research and Development Program of China , doi 10.13039/501100012166;
                Award ID: 2016YFC1300504
                Funded by: the National Science and Technology Innovation 2030 ‐‐ Major program of “Brain Science and Brain‐Like Research”
                Award ID: 2022ZD0211800
                Categories
                Research Article
                Research Articles
                Custom metadata
                2.0
                April 15, 2023
                Converter:WILEY_ML3GV2_TO_JATSPMC version:6.2.6 mode:remove_FC converted:21.03.2023

                Neurology
                cognitive impairment,default mode network,resting‐state functional mri,subsystem,white matter hyperintensity

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