Synaptic learning models of map separation in the hippocampus

When rats trained to forage in one environment are exposed to a second, highly similar environment, their hippocampal place code exhibits a partial remapping in the new environment that becomes more complete with repeated exposures (Tanila, Shapiro, and Eichenbaum, 1997; Bostock, Muller, and Kubie, 1991). If the perforant path projection to CA3 functions as a pattern completion mechanism, and the DG projection via the mossy bers performs pattern separation (O'Reilly and McClelland, 1994), then partial remapping can be understood as the combined e ect of these two projections. We investigated learning rules that could be responsible for the gradual separation of two maps, and found that, while simple Hebbian learning and Hebbian covariance learning would not produce the separation e ect, BCM learning was one rule that would.