A comparison of learning and memory characteristics of young and middle-aged wild-type mice in the IntelliCage.

We have tested the cognitive abilities of young (2.5 months) and middle-aged (14 months) wild-type C57Bl/6J mice in the IntelliCage, which enables automated monitoring of spontaneous and learning behaviour in a homecage-like environment. No differences were observed either in circadian activity or in performance in the novelty-induced exploration test, but middle-aged mice exhibited decreased exploratory activity overall. In the place learning test module, when mice were free to explore all corners without any negative reinforcement, young mice tended not to learn the task and performed less effectively than the middle-aged group. However, when an air-puff was administered as negative reinforcement following visits to an incorrect corner, young mice learned the task significantly better than middle-aged mice throughout the test period. Our data show that, in freely moving mice, the motivational cues for learning and retrieval of memory are age-dependent and dramatically influence learning and memory performance. Furthermore, the data reported here represent a step towards optimised cognitive test protocols when comparing young and middle-aged mice.