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Journal of Neurophysiology Nov 2016Whereas the cerebral cortex has long been regarded by neuroscientists as the major locus of cognitive function, the white matter of the brain is increasingly recognized... (Review)
Review
Whereas the cerebral cortex has long been regarded by neuroscientists as the major locus of cognitive function, the white matter of the brain is increasingly recognized as equally critical for cognition. White matter comprises half of the brain, has expanded more than gray matter in evolution, and forms an indispensable component of distributed neural networks that subserve neurobehavioral operations. White matter tracts mediate the essential connectivity by which human behavior is organized, working in concert with gray matter to enable the extraordinary repertoire of human cognitive capacities. In this review, we present evidence from behavioral neurology that white matter lesions regularly disturb cognition, consider the role of white matter in the physiology of distributed neural networks, develop the hypothesis that white matter dysfunction is relevant to neurodegenerative disorders, including Alzheimer's disease and the newly described entity chronic traumatic encephalopathy, and discuss emerging concepts regarding the prevention and treatment of cognitive dysfunction associated with white matter disorders. Investigation of the role of white matter in cognition has yielded many valuable insights and promises to expand understanding of normal brain structure and function, improve the treatment of many neurobehavioral disorders, and disclose new opportunities for research on many challenging problems facing medicine and society.
Topics: Animals; Cognition; Humans; Nerve Net; Neural Pathways; White Matter
PubMed: 27512019
DOI: 10.1152/jn.00221.2016 -
NeuroImage Nov 2018Throughout infancy, childhood, and adolescence, our brains undergo remarkable changes. Processes including myelination and synaptogenesis occur rapidly across the first... (Review)
Review
Throughout infancy, childhood, and adolescence, our brains undergo remarkable changes. Processes including myelination and synaptogenesis occur rapidly across the first 2-3 years of life, and ongoing brain remodeling continues into young adulthood. Studies have sought to characterize the patterns of structural brain development, and early studies predominately relied upon gross anatomical measures of brain structure, morphology, and organization. MRI offers the ability to characterize and quantify a range of microstructural aspects of brain tissue that may be more closely related to fundamental neurodevelopmental processes. Techniques such as diffusion, magnetization transfer, relaxometry, and myelin water imaging provide insight into changing cyto- and myeloarchitecture, neuronal density, and structural connectivity. In this review, we focus on the growing body of literature exploiting these MRI techniques to better understand the microstructural changes that occur in brain white matter during maturation. Our review focuses on studies of normative brain development from birth to early adulthood (∼25 years), and places particular emphasis on longitudinal studies and newer techniques that are being used to study microstructural white matter development. All imaging methods demonstrate consistent, rapid microstructural white matter development over the first 3 years of life, suggesting increased myelination and axonal packing. Diffusion studies clearly demonstrate continued white matter maturation during later childhood and adolescence, though the lack of consistent findings in other modalities suggests changes may be mainly due to axonal packing. An emerging literature details differential microstructural development in boys and girls, and connects developmental trajectories to cognitive abilities, behaviour, and/or environmental factors, though the nature of these relationships remains unclear. Future research will need to focus on newer imaging techniques and longitudinal studies to provide more detailed information about microstructural white matter development, particularly in the childhood years.
Topics: Adolescent; Adult; Child; Child, Preschool; Human Development; Humans; Infant; Magnetic Resonance Imaging; Neuroimaging; White Matter; Young Adult
PubMed: 29305910
DOI: 10.1016/j.neuroimage.2017.12.097 -
JAMA Pediatrics Jan 2020The American Academy of Pediatrics (AAP) recommends limits on screen-based media use, citing its cognitive-behavioral risks. Screen use by young children is prevalent...
IMPORTANCE
The American Academy of Pediatrics (AAP) recommends limits on screen-based media use, citing its cognitive-behavioral risks. Screen use by young children is prevalent and increasing, although its implications for brain development are unknown.
OBJECTIVE
To explore the associations between screen-based media use and integrity of brain white matter tracts supporting language and literacy skills in preschool-aged children.
DESIGN, SETTING, AND PARTICIPANTS
This cross-sectional study of healthy children aged 3 to 5 years (n = 47) was conducted from August 2017 to November 2018. Participants were recruited at a US children's hospital and community primary care clinics.
EXPOSURES
Children completed cognitive testing followed by diffusion tensor imaging (DTI), and their parent completed a ScreenQ survey.
MAIN OUTCOMES AND MEASURES
ScreenQ is a 15-item measure of screen-based media use reflecting the domains in the AAP recommendations: access to screens, frequency of use, content viewed, and coviewing. Higher scores reflect greater use. ScreenQ scores were applied as the independent variable in 3 multiple linear regression models, with scores in 3 standardized assessments as the dependent variable, controlling for child age and household income: Comprehensive Test of Phonological Processing, Second Edition (CTOPP-2; Rapid Object Naming subtest); Expressive Vocabulary Test, Second Edition (EVT-2; expressive language); and Get Ready to Read! (GRTR; emergent literacy skills). The DTI measures included fractional anisotropy (FA) and radial diffusivity (RD), which estimated microstructural organization and myelination of white matter tracts. ScreenQ was applied as a factor associated with FA and RD in whole-brain regression analyses, which were then narrowed to 3 left-sided tracts supporting language and emergent literacy abilities.
RESULTS
Of the 69 children recruited, 47 (among whom 27 [57%] were girls, and the mean [SD] age was 54.3 [7.5] months) completed DTI. Mean (SD; range) ScreenQ score was 8.6 (4.8; 1-19) points. Mean (SD; range) CTOPP-2 score was 9.4 (3.3; 2-15) points, EVT-2 score was 113.1 (16.6; 88-144) points, and GRTR score was 19.0 (5.9; 5-25) points. ScreenQ scores were negatively correlated with EVT-2 (F2,43 = 5.14; R2 = 0.19; P < .01), CTOPP-2 (F2,35 = 6.64; R2 = 0.28; P < .01), and GRTR (F2,44 = 17.08; R2 = 0.44; P < .01) scores, controlling for child age. Higher ScreenQ scores were correlated with lower FA and higher RD in tracts involved with language, executive function, and emergent literacy abilities (P < .05, familywise error-corrected), controlling for child age and household income.
CONCLUSIONS AND RELEVANCE
This study found an association between increased screen-based media use, compared with the AAP guidelines, and lower microstructural integrity of brain white matter tracts supporting language and emergent literacy skills in prekindergarten children. The findings suggest further study is needed, particularly during the rapid early stages of brain development.
Topics: Child, Preschool; Cross-Sectional Studies; Diffusion Tensor Imaging; Female; Humans; Male; Neuropsychological Tests; Screen Time; United States; White Matter
PubMed: 31682712
DOI: 10.1001/jamapediatrics.2019.3869 -
Aging Mar 2023
Topics: Humans; White Matter; Facial Pain; Chronic Pain
PubMed: 36934329
DOI: 10.18632/aging.204584 -
Frontiers in Immunology 2022Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in... (Review)
Review
Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in depressive disorder could be a result of impaired cerebral blood flow (CBF) and CBF self-regulation, impaired blood-brain barrier function, inflammatory factors, genes and environmental factors. Additionally, white matter changes in patients with depression are associated with clinical variables such as differential diagnosis, severity, treatment effect, and efficacy assessment. This review discusses the characteristics, possible mechanisms, clinical relevance, and potential treatment of white matter alterations caused by depressive disorders.
Topics: Cerebrovascular Circulation; Depressive Disorder; Humans; White Matter
PubMed: 35634314
DOI: 10.3389/fimmu.2022.826812 -
Current Opinion in Neurology Dec 2020In the study of brain-injured patients with disorders of consciousness (DoC), structural and functional MRI seek to provide insights into the neural correlates of... (Review)
Review
PURPOSE OF REVIEW
In the study of brain-injured patients with disorders of consciousness (DoC), structural and functional MRI seek to provide insights into the neural correlates of consciousness, identify neurophysiologic signatures of covert consciousness, and identify biomarkers for recovery of consciousness.
RECENT FINDINGS
Cortical volume, white matter volume and integrity, and structural connectivity across many grey and white matter regions have been shown to vary with level of awareness in brain-injured patients. Resting-state functional connectivity (rs-FC) within and between canonical cortical networks also correlates with DoC patients' level of awareness. Stimulus-based and motor-imagery fMRI paradigms have identified some behaviorally unresponsive DoC patients with cortical processing and activation patterns that mirror healthy controls. Emerging techniques like dynamic rs-FC have begun to identify temporal trends in brain-wide connectivity that may represent novel neural correlates of consciousness.
SUMMARY
Structural and functional MRI will continue to advance our understanding of brain regions supporting human consciousness. Measures of regional and global white matter integrity and rs-FC in particular networks have shown significant improvement over clinical features in identifying acute and chronic DoC patients likely to recover awareness. As they are refined, functional MRI paradigms may additionally provide opportunities for interacting with behaviorally unresponsive patients.
Topics: Brain; Consciousness; Consciousness Disorders; Humans; Magnetic Resonance Imaging; White Matter
PubMed: 33044234
DOI: 10.1097/WCO.0000000000000873 -
Neurology May 2019To determine whether free water (FW) content, initially developed to correct metrics derived from diffusion tensor imaging and recently found to be strongly associated...
OBJECTIVE
To determine whether free water (FW) content, initially developed to correct metrics derived from diffusion tensor imaging and recently found to be strongly associated with vascular risk factors, may constitute a sensitive biomarker of white matter (WM) microstructural differences associated with cognitive performance but remains unknown.
METHODS
Five hundred thirty-six cognitively diverse individuals, aged 77 ± 8 years, received yearly comprehensive clinical evaluations and a baseline MRI examination of whom 224 underwent follow-up MRI. WM microstructural measures, including FW, fractional anisotropy, and mean diffusivity corrected for FW and WM hyperintensity burden were computed within WM voxels of each individual. Baseline and change in MRI metrics were then used as independent variables to explain baseline and change in episodic memory (EM), executive function (EF), and Clinical Dementia Rating (CDR) scores using linear, logistic, and Cox proportional-hazards regressions.
RESULTS
Higher baseline FW and WM hyperintensity were associated with lower baseline EM and EF, higher baseline CDR, accelerated EF and EM decline, and higher probability to transition to a more severe CDR stage ( values <0.01). Annual change in FW was also found to be associated with concomitant change in cognitive and functional performance ( values <0.01).
CONCLUSIONS
This study finds cross-sectional and longitudinal associations between FW content and trajectory of cognitive and functional performance in a large sample of cognitively diverse individuals. It supports the need to investigate the pathophysiologic process that manifests increased FW, potentially leading to more severe WM territory injury and promoting cognitive and functional decline.
Topics: Aged; Aged, 80 and over; Anisotropy; Biomarkers; Brain; Cognition; Cross-Sectional Studies; Executive Function; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neuropsychological Tests; Water; White Matter
PubMed: 30952798
DOI: 10.1212/WNL.0000000000007449 -
Functional Neurology 2016Quantitative magnetic resonance imaging can be combined with advanced biophysical models to measure microstructural features of white matter. Non-invasive... (Review)
Review
Quantitative magnetic resonance imaging can be combined with advanced biophysical models to measure microstructural features of white matter. Non-invasive microstructural imaging has the potential to revolutionize neuroscience, and acquiring these measures in clinically feasible times would greatly improve patient monitoring and clinical studies of drug efficacy. However, a good understanding of microstructural imaging techniques is essential to set realistic expectations and to prevent over-interpretation of results. This review explains the methodology behind microstructural modeling and imaging, and gives an overview of the breakthroughs and challenges associated with it.
Topics: Brain; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Models, Neurological; White Matter
PubMed: 28072382
DOI: 10.11138/fneur/2016.31.4.217 -
BioMed Research International 2017Hypertensive intracerebral hemorrhage (ICH) could very probably trigger white matter injury in patients. Through the continuous study of white matter injury after... (Review)
Review
Hypertensive intracerebral hemorrhage (ICH) could very probably trigger white matter injury in patients. Through the continuous study of white matter injury after hypertensive ICH, we achieve a more profound understanding of the pathophysiological mechanism of its occurrence and development. At the same time, we found a series of drugs and treatment methods for the white matter repair. In the current reality, the research paradigm of white matter injury after hypertensive ICH is relatively obsolete or incomplete, and there are still lots of deficiencies in the research. In the face of the profound changes of stroke research perspective, we believe that the combination of the lenticulostriate artery, nerve nuclei of the hypothalamus-thalamus-basal ganglia, and the white matter fibers located within the capsula interna will be beneficial to the research of white matter injury and repair. This paper has classified and analyzed the study of white matter injury and repair after hypertensive ICH and also rethought the shortcomings of the current research. We hope that it could help researchers further explore and study white matter injury and repair after hypertensive ICH.
Topics: Animals; Cerebral Hemorrhage; Female; Humans; Hypertension; Male; Stroke; White Matter
PubMed: 28680884
DOI: 10.1155/2017/6138424 -
CNS Neuroscience & Therapeutics Oct 2019The predilection site of intracerebral hemorrhage (ICH) is in the basal ganglia, which is rich in white matter (WM) fiber bundles, such as cerebrospinal tract in the... (Review)
Review
The predilection site of intracerebral hemorrhage (ICH) is in the basal ganglia, which is rich in white matter (WM) fiber bundles, such as cerebrospinal tract in the internal capsule. ICH induced damage to this area can easily lead to severe neurological dysfunction and affects the prognosis and quality of life of patients. At present, the pathophysiological mechanisms of white matter injury (WMI) after ICH have attracted researchers' attention, but studies on the repair and recovery mechanisms and therapy strategies remain rare. In this review, we mainly summarized the WM recovery and treatment strategies after ICH by updating the WMI-related content by reviewing the latest researches and proposing the bottleneck of the current research.
Topics: Animals; Brain; Cerebral Hemorrhage; Genetic Therapy; Humans; Neuroprotective Agents; Stem Cell Transplantation; White Matter
PubMed: 31578825
DOI: 10.1111/cns.13226