Evaluating the temporal context of episodic memory: the role of CA3 and CA1.

It has been suggested that the hippocampus mediates episodic memory processing involving snapshot memory and temporal sequence learning. To test this theory, rats learned trial-unique sequences of spatial locations along a runway box and were tested on recall by removing one of the locations in the sequence and making the rat choose the correct location to be rewarded. Once animals were able to reliably perform this episodic memory task, they received lesions to either CA3 or CA1. Animals with lesions to either CA3 or CA1 had difficulty with episodic memory processing, although CA1 lesioned animals had a much greater deficit. However, when animals were trained on a non-episodic version of the same task, hippocampal lesions had no effect. These results suggest that CA3 and CA1 both contribute to episodic memory processing since lesions to CA3 or CA1 result in an inability to process spatial information episodically, whereas they have no effect on non-episodic information processing.