AGE-RELATED DEFICITS IN RETENTION OF THE CLASSICALLY-CONDITIONED NICTITATING-MEMBRANE RESPONSE IN RABBITS

Young and aged rabbits underwent classical conditioning of the nictita ting membrane response (NMR) to a tone conditioned stimulus (CS) and a corneal airpuff unconditioned stimulus (UCS) for 18 consecutive days. Rabbits were then returned to their home cages for a 90-day period in which they received no further conditioning, but they were handled da ily. On Day 91 they underwent retention testing during which the CS al one was presented 20 times. This was immediately followed by reacquisi tion in which the CS and UCS were again paired for 100 trials. Reacqui sition was repeated on the following day. As in previous studies, aged rabbits acquired the conditioned response (CR) more slowly than young rabbits; however, by the end of acquisition, both groups reached simi lar asymptotic levels. Retention of the CR was significantly lower for aged than young rabbits. Reacquisition was also retarded in aged vs. young rabbits. Nonassociative factors, such as sensitivity to the stim uli or general health, could not account for these differences. Data a re discussed in terms of using retention of the conditioned eyeblink r esponse as a model system for studying age-related memory deficits.