MRI data read as normal on 88 male and female patients aged 3 months to 30 years and on 73 healthy male volunteers aged 21 to 70 years were quantified and the volumes of cortical white matter, gray matter, and CSF were computed in a study at the Department of Veterans Affairs Medical Center, and the Department of Psychiatry and Behavioral Science, Stanford University School of Medicine, CA. In the younger samples, obtained from four California clinics, intracranial volume increased by about 300 ml from 3 months to 10 years. Head size of boys was larger than that of girls by about 70 mL, but both sexes followed the same growth trend. Cortical gray matter volume peaked at age 4 years and decreased thereafter; cortical white matter volume increased steadily until age 20 years: cortical and ventricular CSF volumes remained constant. In the older sample, cortical gray matter volume decreased curvilinearly by 0.7 mL/year, while white matter volume remained constant through 5 decades. Cortical CSF volume increased by 0.6 mL/y and ventricular volumes increased by 0.3 mL/y as cortical gray matter decreased. 
COMMENT. Age-related changes in gray-white matter ratio suggest that growth in white matter exceeds that of gray during the first 5 years, continues to expand until age 20 years, whereas gray matter volume declines after age 5. Age 4 years marks the end of gray matter growth and the beginning of a consistent decline throughout the life span. A relation between head size and cortical gray matter is established early and persists into late adulthood. These quantitative studies of normal brain development, reflecting cell growth and death, myelination, and atrophy, provide important comparative data in the investigation of neurodegenerative processes.