scholarly journals Microstructure of Human Corpus Callosum across the Lifespan: Regional Variations in Axon Caliber, Density, and Myelin Content

2020 ◽  
Author(s):  
Jonathan D Lynn ◽  
Chaitali Anand ◽  
Muzamil Arshad ◽  
Roya Homayouni ◽  
David R Rosenberg ◽  
...  
Keyword(s):  
Corpus Callosum ◽  
Age Differences ◽  
Geometric Mean ◽  
Large Diameter ◽  
Fiber Density ◽  
Regional Patterns ◽  
Water Fraction ◽  
Age Related ◽  
Developmental Progression ◽  
Myelin Water Fraction

Abstract The myeloarchitecture of the corpus callosum (CC) is characterized as a mosaic of distinct differences in fiber density of small- and large-diameter axons along the anterior–posterior axis; however, regional and age differences across the lifespan are not fully understood. Using multiecho T2 magnetic resonance imaging combined with multi-T2 fitting, the myelin water fraction (MWF) and geometric-mean of the intra-/extracellular water T2 (geomT2IEW) in 395 individuals (7–85 years; 41% males) were examined. The approach was validated where regional patterns along the CC closely resembled the histology; MWF matched mean axon diameter and geomT2IEW mirrored the density of large-caliber axons. Across the lifespan, MWF exhibited a quadratic association with age in all 10 CC regions with evidence of a positive linear MWF-age relationship among younger participants and minimal age differences in the remainder of the lifespan. Regarding geomT2IEW, a significant linear age × region interaction reflected positive linear age dependence mostly prominent in the regions with the highest density of small-caliber fibers—genu and splenium. In all, these two indicators characterize distinct attributes that are consistent with histology, which is a first. In addition, these results conform to rapid developmental progression of CC myelination leveling in middle age as well as age-related degradation of axon sheaths in older adults.

scholarly journals LIFESPAN AGE-RELATED DIFFERENCES IN THE REGIONAL WHITE MATTER MICROSTRUCTURE OF THE HUMAN CORPUS CALLOSUM

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S945-S945
Author(s):  
John Lynn ◽  
Chaitali Anand ◽  
Muzamil Arshad ◽  
Dalal Khatib ◽  
Jeffrey Stanley ◽  
...  
Keyword(s):  
White Matter ◽  
Corpus Callosum ◽  
Geometric Mean ◽  
Age Groups ◽  
Fiber Density ◽  
Linear Effect ◽  
Water Fraction ◽  
General Linear Model Analysis ◽  
Age Related ◽  
Axonal Density

Abstract The corpus callosum (CC) connects homologous cortical structures across hemispheres and is the largest white matter tract in the human brain. Post-mortem studies suggest that CC myelination begins in infancy, reaches a plateau in the middle age, and declines in the later years. The latter is accompanied by myelin disruption and reduction in fiber density and diameter, i.e. changes in intra-/extracellular water space. We used multi-echo T2 imaging to estimate, via multi-exponential T2 relaxation of water, the myelin water fraction (MWF), a direct proxy for myelin content, and geometric mean T2 (geomT2IEW) that reflects water in the intra-/extracellular space, to investigate age differences in five CC regions covering its anterior to posterior span in 395 healthy individuals (7-85 years; 161M+235F). The general linear model analysis of MWF showed main effects of age and age-squared conditioned on interactions by CC region. Univariate polynomial regressions on three age groups (7-29, 30-59, and 60-85 years) revealed the overall quadratic association between age and MWF as mainly driven by the positive linear relationship in the youngest group and minimal differences in the remainder of the lifespan, save for two weak negative linear associations in the anterior/middle CC body. With geomT2, a main linear effect of age, and significant interactions between age and age-squared by region were observed. The positive linear association was especially prominent in the regions with greater fiber density. The results are consistent with CC myelination into adulthood and decreased axonal density and diameter but not prominent myelin degeneration in elderly individuals.

scholarly journals Multicenter measurements of myelin water fraction and geometric mean T2: Intra- and intersite reproducibility

2013 ◽  
Vol 38 (6) ◽  
pp. 1445-1453 ◽  
Author(s):  
Sandra M. Meyers ◽  
Irene M. Vavasour ◽  
Burkhard Mädler ◽  
Trudy Harris ◽  
Eric Fu ◽  
...  
Keyword(s):  
Geometric Mean ◽  
Water Fraction ◽  
Myelin Water Fraction

scholarly journals Age-Related Measurements of the Myelin Water Fraction derived from 3D multi-echo GRASE reflect Myelin Content of the Cerebral White Matter

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Tobias D. Faizy ◽  
Dushyant Kumar ◽  
Gabriel Broocks ◽  
Christian Thaler ◽  
Fabian Flottmann ◽  
...  
Keyword(s):  
White Matter ◽  
Cerebral White Matter ◽  
Water Fraction ◽  
Age Related ◽  
Myelin Water Fraction

Myelin Water Fraction and Intra/Extracellular Water Geometric Mean T 2 Normative Atlases for the Cervical Spinal Cord from 3T MRI

2019 ◽  
Vol 30 (1) ◽  
pp. 50-57 ◽  
Author(s):  
Hanwen Liu ◽  
Emil Ljungberg ◽  
Adam V. Dvorak ◽  
Lisa Eunyoung Lee ◽  
Jackie T. Yik ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Cervical Spinal Cord ◽  
Geometric Mean ◽  
Extracellular Water ◽  
3T Mri ◽  
Water Fraction ◽  
Myelin Water Fraction

scholarly journals Age-Related Differences in White Matter: Understanding Tensor-Based Results Using Fixel-Based Analysis

2021 ◽  
Author(s):  
Shannon Kelley ◽  
John Plass ◽  
Andrew R Bender ◽  
Thad A Polk
Keyword(s):  
White Matter ◽  
Age Differences ◽  
Diffusion Tensor ◽  
Internal Capsule ◽  
Cerebral White Matter ◽  
Fiber Density ◽  
Cingulum Bundle ◽  
Age Related ◽  
Structural Differences ◽  
Diffusion Tensor Imaging Dti

Abstract Aging is associated with widespread alterations in cerebral white matter (WM). Most prior studies of age differences in WM have used diffusion tensor imaging (DTI), but typical DTI metrics (e.g., fractional anisotropy; FA) can reflect multiple neurobiological features, making interpretation challenging. Here, we used fixel-based analysis (FBA) to investigate age-related WM differences observed using DTI in a sample of 45 older and 25 younger healthy adults. Age-related FA differences were widespread but were strongly associated with differences in multi-fiber complexity (CX), suggesting that they reflected differences in crossing fibers in addition to structural differences in individual fiber segments. FBA also revealed a frontolimbic locus of age-related effects and provided insights into distinct microstructural changes underlying them. Specifically, age differences in fiber density were prominent in fornix, bilateral anterior internal capsule, forceps minor, body of the corpus callosum, and corticospinal tract, while age differences in fiber cross section were largest in cingulum bundle and forceps minor. These results provide novel insights into specific structural differences underlying major WM differences associated with aging.

scholarly journals Myelin water fraction decrease in individuals with chronic mild traumatic brain injury and persistent symptoms

Heliyon ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. e06709
Author(s):  
Bretta Russell-Schulz ◽  
Irene M. Vavasour ◽  
Jing Zhang ◽  
Alex L. MacKay ◽  
Victoria Purcell ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Mild Traumatic Brain Injury ◽  
Water Fraction ◽  
Persistent Symptoms ◽  
Myelin Water Fraction

Age Differences in the Social Associative Learning of Trust Information

2022 ◽  
Author(s):  
Kendra Leigh Seaman ◽  
Alexander P. Christensen ◽  
Katherine Senn ◽  
Jessica Cooper ◽  
Brittany Shane Cassidy
Keyword(s):  
Older Adults ◽  
Age Differences ◽  
Social Cues ◽  
Trust Game ◽  
Time Model ◽  
Younger Adults ◽  
Cortical Areas ◽  
Age Related ◽  
The Social ◽  
Over Time

Trust is a key component of social interaction. Older adults, however, often exhibit excessive trust relative to younger adults. One explanation is that older adults may learn to trust differently than younger adults. Here, we examine how younger (N=33) and older adults (N=30) learn to trust over time. Participants completed a classic iterative trust game with three partners. Younger and older adults shared similar amounts but differed in how they shared money. Compared to younger adults, older adults invested more with untrustworthy partners and less with trustworthy partners. As a group, older adults displayed less learning than younger adults. However, computational modeling shows that this is because older adults are more likely to forget what they have learned over time. Model-based fMRI analyses revealed several age-related differences in neural processing. Younger adults showed prediction error signals in social processing areas while older adults showed over-recruitment of several cortical areas. Collectively, these findings suggest that older adults attend to and learn from social cues differently from younger adults.

Brain myelin water fraction is associated with APOE4 allele status in patients with cognitive impairment

2021 ◽  
Author(s):  
Mina Park ◽  
Hong Pyo Lee ◽  
Junghyeob Kim ◽  
Dong Hyun Kim ◽  
Yeonsil Moon ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Water Fraction ◽  
Apoe4 Allele ◽  
Allele Status ◽  
Myelin Water Fraction
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