The Object Space Task shows cumulative memory expression in both mice and rats

ABSTRACT Declarative memory encompasses representations of specific events as well as knowledge extracted by accumulation over multiple episodes. To investigate how these different sorts of memories are created, we developed a new behavioral task in rodents. The task consists of three distinct conditions (stable, overlapping, random). Rodents are exposed to multiple sample trials, in which they explore objects in specific spatial arrangements. In the stable condition, the locations are constant during all sample trials; in the test trial, one object’s location is changed. In the random condition, object locations are presented in the sample phase without a specific spatial pattern. In the overlapping condition, one location is shared (overlapping) between all trials while the other location changes during sample trials. We show that in the overlapping condition, instead of only remembering the last sample trial, rodents form a cumulative memory of the sample trials. Here we could show that both mice and rats can accumulate information across multiple trials and express a long-term abstracted memory.