Regional cerebral blood flow characteristics and variations with age in resting normal subjects.

Regional cerebral blood flow (rCBF) was measured during resting in 97 normal subjects, 19-68 years old. The results showed that the mean CBF level decreased progressively with age. The decrease was more prominent in frontotemporal and inferior Rolandic areas bilaterally. Frontal areas showed the highest values in all age groups. This hyperfrontality weakened somewhat with age. Mean CBF in the right hemisphere was significantly higher than in the left, as was flow in superior frontal, inferior frontal, and parietal areas. These asymmetries were age invariant. The age-related decrease of rCBF is interpreted as reflecting aging of the brain per se, although the influence of asymptomatic brain disease can not be ruled out. The flow asymmetries are interpreted as being related to functional lateralization of some aspects of attentional activation.