Modelling of What-Where-When Everyday Memories in Rats

Episodic memories contain information about the nature of an event, the place where it happened and the time when it occurred. In animals, the term ‘episodic-like memory’ is preferred to refer to mnemonic instances containing these three features, commonly referred to as ‘what-where-when’. Models to study episodic-like memory have been proposed in corvidae and rodents, although their use in neuroscience research has been limited due to certain limitations and potential ambiguities. Although the neurological correlates of ‘what-where-when’ have been identified in neuronal types such as place and time cells, it is unclear how they contribute to form a unitary representation or how this information can be accessed during memory recall, either holistically or differentially. Here, we outline two new behavioural paradigms based on the everyday memory task that we have developed to model what and when components as well as ‘where’ information. In Experiment 1 (E1), we demonstrate that rats are able to learn two distinct food positions on a daily basis and retrieve them independently. In E2, we establish that rats can learn that two flavours are replenished at different times after an initial sampling, thus using the temporal component to guide their decision making. These two tasks can therefore provide the basis to study how the item, location and time information of a memory are stored and accessed by the brain. This should be observable in single-unit recording or calcium-imaging studies.