Age-related changes in brain: II. Positron emission tomography of frontal and temporal lobe glucose metabolism in normal subjects.

While many neuropsychological studies have demonstrated age-related performance alterations in tests thought to reflect frontal and temporal lobe function, there is little direct observation and comparison of these hypothesized brain changes in vivo. The cerebral glucose metabolism of frontal, temporal, and cerebellar regions was examined in 40 young (mean = 27.5 +/- 4.9) and 31 elderly (mean = 67.6 +/- 8.8) normal males using PET-FDG. Univariate analysis showed age-related metabolic reductions in all frontal and temporal lobe regions. The reductions ranged from 13%-24% with the greatest changes in the frontal lobes. Multiple regression analyses showed a stronger age relationship with frontal lobe than with temporal lobe metabolism. The dorsal lateral frontal lobe was the region that appears to change most within the frontal lobes. Examination of the temporal lobe showed that age contributed equally to the metabolic variance of both the lateral temporal lobe and hippocampus. These results suggest that age-related metabolic changes exist in both frontal and temporal lobes and that the frontal lobe change is greater.