Cognitive Aging in Nonhuman Primates

The study of cognitive aging in nonhuman primates provides a model system for understanding normal cognitive aging in humans, as well as the ability to examine specific potential neurobiological substrates of age-related cognitive impairment. This chapter reviews the evidence for age-related changes in five cognitive domains in nonhuman primates: visual recognition memory, spatial memory, stimulus–reward associative learning, relational memory, and attention/executive function. The effects of damage to specific neural systems on the performance of the particular behavioral tasks used to assess each of these domains are compared to the effects of aging on these tasks. The behavioral profile of aged monkeys is consistent with dysfunction of an inferior temporal-ventromedial prefrontal system for recognition memory and stimulus–reward associative learning, as well as deficits in dorsolateral prefrontal and/or hippocampal function contributing to spatial memory impairment, hippocampal system function contributing to relational memory impairment, and frontal lobe function contributing to executive system dysfunction. The declines in these systems seem to be at least partially independent of each other with increasing age. A focus on individual differences in the profiles of cognitive impairment in aged monkeys, and examination of relationships between behavioral and neurobiological parameters independently of main effects of age on these measures, might provide further insight into the biological basis of cognitive aging.