Figure 3d. Graphs depict growth and aging changes in (a) GM and (b) WM volumes in 116 living healthy volunteers. Volume intercepts at birth are based on the findings of Huppi et al (55). (On x axes, age scales change after 20-year point.) GM volume reached a maximum by 6-9 years of age and thereafter declined linearly. WM volume rapidly increased until 12-15 years of age, and thereafter increased at a slower rate to a plateau at about the 4th decade of life. For both (c) the present in vivo and (d) the published MR imaging and postmortem data, the GW-WM ratio drops sharply from infancy to about the end of adolescence after which it declines at a slower rate. Symbols in d represent data from the postmortem studies of Anton (49) (
), Jaeger (50) (
), and Miller et al (25) (*) and the MR imaging studies of Filipek et al (51) (
= data in males, 
= data in females), Pfefferbaum et al (27) (
), and Narayana and Borthakur (52) (
).