CONTEXT PROVIDES A STRONGER RETRIEVAL CUE THAN SEQUENCE FOR RETRIEVAL OF EPISODIC-LIKE MEMORY EVENTS IN MICE

Episodic memory is a fundamental cognitive capacity, with deficits being one of the earliest symptoms of Alzheimer's disease. Episodic memory allows us to store and retrieve memories for specific events including the spatiotemporal details of the event. However, while the spatial location of an event is easy to define the temporal component can be defined in many ways including specific time stamps, sequence information and contextual cues present at the time of encoding. Here we test whether two of these sources of temporal information (sequence and context) are better cues for supporting subsequent retrieval of memory for an event. Mice were exposed to objects within 2 sample sessions. The testing environment was always located in the same location but could be configured in two contextual setups with different floors. The two sample sessions could, therefore, be distinguished using either sequence of presentation or context information. Test trails could then be used to probe whether mice preferentially use sequence or context information in their episodic-like memory. In simple tests mice were able to use either sequence or context information to support memory for the test trials. However, when the two cues were put in conflict, context provided a stronger cue for memory than the sequence in which objects were presented. Interestingly, providing both context and sequence information did not improve memory relative to the simple tests. These findings show that context is used in preference to sequence information to support episodic-like memory in mice.