The brain undergoes dramatic changes during puberty and pregnancy, but during menopause, the organ's structure remains remarkably stable, a new study suggests. The research, published Sept. 8 in the journal Nature Communications, examined the brain's gray matter, which mostly includes the wrinkled outer surface of the organ, called the cerebral cortex. Past studies have found that the volume of gray matter shrinks markedly during puberty and pregnancy, likely reflecting a fine-tuning of neural circuits during those periods.There's also a gradual decline in gray matter during adulthood that's seen as a normal part of aging, said study co-author Sophie van't Hof, a doctoral student in psychiat...