Differences in age trajectories of intracortical myelin across lifespan measured by MTR and T1w/T2w

In a large cohort of healthy participants (N=349, age range 18-90 years), we characterized intracortical myelin lifespan trajectories using two commonly used myelin proxies, magnetization transfer ratio (MTR) and T1w/T2w, combined with a surface-based image processing method. We showed that both measures exhibit an inverted-U shape trajectory for most cortical regions, with T1w/T2w values peaking later than MTR. A smoothed spline fitting of the trajectories allowed further delineation of onset decline age, a potential aging milestone. Frontal and temporal lobe regions showed consistently later peak ages than parietal and sensory motor regions across MRI metrics and curve fitting methods.