A double dissociation between hippocampal subfields: differential time course of CA3 and CA1 place cells for processing changed environments.

Computational theories have suggested different functions for the hippocampal subfields (e.g., CA1 and CA3) in memory. However, it has been difficult to find dissociations relevant to these hypothesized functions in investigations of the hippocampal correlates of space ("place fields") in freely behaving animals. The current study demonstrates a double dissociation between the shifts in the center of mass (COM) of the place fields that were simultaneously recorded in CA1 and CA3 when familiar cue configurations were dynamically changed over days. The COM of CA3 place fields shifted backward in the first experience of the cue-changed environment, whereas the COM of CA1 place fields did not display the backward shift until the next day. These results support the hypothesis that CA3 plays a key role in the rapid formation of representations of new spatiotemporal sequences, whereas CA1 may be more important for comparing currently experienced sequence information with stored sequences in the CA3 network.