Synaptic and mitochondrial morphometry provides structural correlates of successful brain aging.

Average synaptic size (S), synaptic numeric density (Nv) and surface density (Sv), average mitochondrial volume, mitochondrial numeric density, and mitochondrial volume density were measured by morphometry in the frontal (FC) and temporal (TC) cortex from adult and old monkeys (Macaca fascicularis). In relation to aging, Sv did not change, while Nv was significantly decreased in TC, but not in FC. S was significantly increased in FC and TC. No significant difference due to age was found with regard to mitochondrial ultrastructure. Considering the functional significance of the above parameters, their substantial age-related constancy suggests that they may reasonably represent structural correlates of successful brain aging.