The weight of the infratentorial portion of the adult brain and analysis of the infratentorial/whole brain weight ratio.
A direct relationship exists between the weights of the infratentorial portion (ITP) of the brain and the whole brain. With aging, the weight of the ITP decreases, but the decrease begins later and is smaller than for the forebrain. With whole brain weights, there are significant differences in the weight of the ITP between sexes and between the races. The weight of the ITP increases slightly with increase in body weight. The infratentorial/whole brain ratio is stable during adult life and does not vary with body dimensions. The ratio increases after age 80 because of the accelerated loss of mass of the forebrain. The ratio is the same for both races, but it is significantly higher for the females than for the males. The difference is best accounted for by an arrest in the growth of the forebrain in the female during adolescence.
D000328:Adult; D000367:Age Factors; D001921:Brain / Q000033:anatomy & histology*; D002531:Cerebellum / Q000033:anatomy & histology; D006801:Humans; D009929:Organ Size; D044469:Racial Groups; D012737:Sex Factors