Impaired recognition memory and decreased prefrontal cortex spine density in aged female rats.

Aged F344 female rats (21 months) showed decreased performance, as compared to young rats (4 months), on an object recognition memory task. Golgi impregnation measured dendritic spine density of pyramidal neurons in the prefrontal cortex (layer II-III), a brain area important for recognition memory. Densities of spines in aged rats were 16% lower in tertiary, apical dendrites, but not significantly different in secondary basal dendrites. Concurrent measures of memory and spine density in the young and aged subjects show that age-related declines in recognition memory are associated with decreased cortical spine density.