Age-related learning and memory deficits in odor-reward association in rats.

In these experiments, potential cognitive deficits in aged rats were studied using an odor-reward association task. Aged Fischer 344 rats first performed to an odor-reward association task. After five daily sessions of 60 trials, the aged rats were globally impaired in comparison to the control rats. However, considering individual performance, 40% of the aged population performed as well as the control animals. These aged rats were then tested for retention at various times. They demonstrated an increased rate of forgetting which was confirmed by a final reversal experiment. The other group of aged rats remained severely impaired and unable to make the odor-reward association correctly until the inter-trial interval was decreased from 15 to 5 s. When they were submitted to a task requiring the learning and retention of 7 new odor pairs, these aged rats again performed poorly. A subsequent reversal session confirmed the rapid forgetting phenomenon for this aged group, even when the odor-reward associations were in fact made.