Cognitive aging: A common decline of episodic recollection and spatial memory in rats

In humans, recognition memory declines with aging, and this impairment is characterized by a selective loss in recollection of previously studied items contrasted with relative sparing of familiarity for items in the study list. Rodent models of cognitive aging have focused on water maze learning and have demonstrated an age-associated loss in spatial, but not cued memory. The current study examined odor recognition memory in young and aged rats and compared performance in recognition with that in water maze learning. In the recognition task, young rats used both recollection and familiarity. In contrast, the aged rats showed a selective loss of recollection and relative sparing of familiarity, similar to the effects of hippocampal damage. Furthermore, performance on the recall component, but not the familiarity component, of recognition was correlated with spatial memory and recollection was poorer in aged rats that were also impaired in spatial memory. These results extend the pattern of impairment in recollection and relative sparing of familiarity observed in human cognitive aging to rats, and suggest a common age-related impairment in both spatial learning and the recollective component of nonspatial recognition memory.