A Novel Task for Studying Memory of Occasional Events in Rats

Episodic memory has been defined in humans as the conscious recollection of unique personal past experiences often occurring singly during daily life, including remembrance of what happened, where and when it happened (Tulving, 1972). Here, we propose and describe in details a novel protocol we recently used to test the ability of rats to form and recollect episodic-like memory of previously encountered occasional episodes (Veyrac et al., 2015). During these episodes, the animals are briefly exposed to sets of specific odor–drink associations (what happened) encountered in specific locations (where it happened) within different multisensory enriched environments (in which context/occasion it happened). Memory of the episodes can be tested at relatively short (24 h) or much longer (24 d) delays in either a low or high interfering retrieval situation. This novel paradigm brought evidence for individual memory profiles of recall performance that might be correlated to different aspects of brain functional networks. More generally, it offers novel possibilities to explore cellular and network mechanisms that underlie memory of past events and memory dysfunction in brain pathologies.