David Smith
Cornell University

Spatial navigation, episodic memory and context processing: what does the hippocampus do?

Although the hippocampus has been the target of intense scrutiny for nearly fifty years, there remains considerable disagreement about the specific functional contribution the hippocampus makes to learning and memory processes. Two of the currently dominant theories suggest that the hippocampus is specialized for spatial navigation or for memory for personally experienced events (episodic memory). However, recent findings from our laboratory indicate that the hippocampus is critically involved in processing contextual information. Although the term 'context' has traditionally been used to refer to the continuously present background stimuli, we have shown that hippocampal neurons are highly sensitive to abstract situational features of the context, such as the task demands. For example, hippocampal neurons exhibit markedly different firing patterns when rats are required to perform different behaviors in the same environment. Since these firing patterns are unique to a given context, they could serve as a neural representation of the context. I will suggest that the hippocampal role in processing spatial information is but one example of a broader function of context processing and that the hippocampus contributes to episodic memory by providing a neural representation of the context, which is, by definition, a critical component of episodic memory.