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Updated: Apr 20, 2026
High-resolution Functional Magnetic Resonance Imaging Methods for Human Midbrain
Published on: May 10, 2012
Gray matter myelination of 1555 human brains using partial volume corrected MRI images
Rebecca Shafee1, Randy L Buckner2, Bruce Fischl3
1Center for Brain Science, Harvard University, Cambridge, MA 02138, USA; Department of Genetics, Harvard Medical School, 77 Ave Louis Pasteur, Boston, MA 02115, USA; Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA.
Abstract:
The myelin content of the cortex changes over the human lifetime and aberrant cortical myelination is associated with diseases such as schizophrenia and multiple sclerosis. Recently magnetic resonance imaging (MRI) techniques have shown potential in differentiating between myeloarchitectonically distinct cortical regions in vivo. Here we introduce a new algorithm for correcting partial volume effects present in mm-scale MRI images which was used to investigate the myelination pattern of the cerebral cortex in 1555 clinically normal subjects using the ratio of T1-weighted (T1w) and T2-weighted (T2w) MRI images. A significant linear cross-sectional age increase in T1w/T2w estimated myelin was detected across an 18 to 35 year age span (highest value of ~ 1%/year compared to mean T1w/T2w myelin value at 18 years). The cortex was divided at mid-thickness and the value of T1w/T2w myelin calculated for the inner and outer layers separately. The increase in T1w/T2w estimated myelin occurs predominantly in the inner layer for most cortical regions. The ratio of the inner and outer layer T1w/T2w myelin was further validated using high-resolution in vivo MRI scans and also a high-resolution MRI scan of a postmortem brain. Additionally, the relationships between cortical thickness, curvature and T1w/T2w estimated myelin were found to be significant, although the relationships varied across the cortex. We discuss these observations as well as limitations of using the T1w/T2w ratio as an estimate of cortical myelin.
Insights
Cortical myelin, a key brain component, increases with age in young adults, predominantly in the inner cortical layer. This finding, observed using advanced MRI, offers insights into normal brain development and aging.
Area of Science:
- Neuroimaging
- Human Brain Development
- Myelination Studies
Background:
- Cortical myelin content changes throughout life.
- Abnormal myelination is linked to neurological disorders like schizophrenia and multiple sclerosis.
- Magnetic resonance imaging (MRI) shows promise for in vivo assessment of cortical myelination.
Purpose of the Study:
- To introduce a novel algorithm for correcting partial volume effects in MRI images.
- To investigate the myelination pattern of the cerebral cortex in a large cohort of healthy adults.
- To analyze age-related changes in cortical myelination.
Main Methods:
- Developed and applied a new algorithm to correct partial volume effects in mm-scale MRI data.
- Utilized the ratio of T1-weighted (T1w) and T2-weighted (T2w) MRI images to estimate myelin content.
- Analyzed data from 1555 clinically normal subjects aged 18-35 years.
- Examined myelin distribution in inner and outer cortical layers.
Main Results:
- A significant linear increase in T1w/T2w estimated myelin was observed with age (approx. 1%/year) between 18 and 35 years.
- Myelin increase primarily occurred in the inner cortical layer across most regions.
- Relationships between cortical thickness, curvature, and myelin content were significant but varied regionally.
- Findings were validated using high-resolution in vivo and postmortem MRI.
Conclusions:
- Cortical myelination shows a distinct age-related increase in early adulthood, concentrated in deeper cortical layers.
- The T1w/T2w ratio, after partial volume correction, provides a viable method for in vivo myelin estimation.
- This research contributes to understanding normal brain maturation and provides a foundation for studying myelin in disease states.
