Synaptic density correlated with maze performance in young and aged rats. A preliminary study

The aim of this study was to determine the effect of age both on maze performance and upon morphological changes in the brain. Young and senescent rats were differentiated into three groups by use of a complex 14-unit maze: young maze-bright rats, old maze-bright animals and old maze-dull rats. Layer III of the frontal and the occipital cortices of these animals was studied, employing coded electron micrographs, to determine the average number of synaptic profiles per area of thin section. It was observed that the young maze-bright rats had the highest synapse density, the old maze-bright rats had 85% of that amount while the old maze-dull animals had a density that was 54% that of the young animals.