Fig. 1.

Quadratic (Inverted U) Trajectories of Human Brain Myelination Over the Lifespan. Myelination (Y-axis) versus age (X-axis) in frontal lobes of normal individuals. Left panel: in vivo MRI data (Bartzokis et al., 2001) using inversion recovery images that are most sensitive to the high cholesterol levels in myelin and are optimal for tracking myelination. Right panel: postmortem myelin stain data of frontal lobe cortex depicting intracortical myelination (from Kaes, 1907 adapted and reproduced in Kemper, 1994). The data were acquired 100 years apart yet the two samples of normal individuals show remarkably similar frontal lobe myelination trajectories, both reaching a peak at age 45. A very similar matching pattern (not shown—see Bartzokis, 2007) is observed in temporal lobe.