Spatial discrimination learning in rats as an animal model of cognitive ageing

Spatial discrimination learning and memory in the rat seems to be a valid animal model for age differences in human cognitive functioning. Inherent to these models are problems concerning the validity of the task and the possible confounding effect of the measures by age differences in non-mnemonic factors such as motor performance, motivation and problem-solving strategies. We have used different tasks such as the holeboard, the conefield and the Morris water-escape task to evaluate spatial discrimination learning in rats of different ages. In the conefield task, we unexpectedly found that old Lewis rats performed better than young Lewis rats on the measure spatial reference memory. In contrast, the performance of old Lewis rats was markedly impaired in the Morris water- escape task compared to that of young Lewis rats. We suggest that the difference in outcome of these two studies is related to confounding variables which have distinct effects in young and old rats. The consequences of these findings for the use of spatial discrimination tasks as an animal model of cognitive ageing are discussed.