Testing declarative memory in laboratory rats and mice using the nonconditioned social discrimination procedure

Testing declarative memory in laboratory rodents can provide insights into the fundamental mechanisms underlying this type of learning and memory processing, and these insights are likely to be applicable to humans. Here we provide a detailed description of the social discrimination procedure used to investigate recognition memory in rats and mice, as established during the last 20 years in our laboratory. The test is based on the use of olfactory signals for social communication in rodents; this involves a direct encounter between conspecifics, during which the investigatory behavior of the experimental subject serves as an index for learning and memory performance. The procedure is inexpensive, fast and very reliable, but it requires well-trained human observers. We include recent modifications to the procedure that allow memory extinction to be investigated by retroactive and proactive interference, and that enable the dissociated analysis of the central nervous processing of the volatile fraction of an individual's olfactory signature. Depending on the memory retention interval under study (short-term memory, intermediate-term memory, long-term memory or long-lasting memory), the protocol takes ~10 min or up to several days to complete.