Plasticity of directional place fields in a model of rodent CA3

We propose a computational model of the CA3 region of the rat hippocampus t hat is able to reproduce the available experimental data concerning the dep endence of directional selectivity of the place cell discharge on the envir onment and on the spatial task. The main feature of our model is a continuo us, unsupervised Hebbian learning dynamics of recurrent connections, which is driven by the neuronal activities imposed upon the network by the enviro nment-dependent external input. In our simulations, the environment and the movements of the rat are chosen to mimic those commonly observed in neurop hysiological experiments. The environment is represented as local views tha t depend on both the position and the heading direction of the rat. We hypo thesize that place cells are intrinsically directional, that is, they respo nd to local views. We show that the synaptic dynamics in the recurrent neur al network rapidly modify the discharge correlates of the place cells: Cell s tend to become omnidirectional place cells in open fields, while their di rectionality tends to get stronger in radial-arm mazes. We also find that t he synaptic learning mechanisms account for other properties of place cell activity, such as an increase in the place cell peak firing rates as well a s clustering of place fields during exploration. Our model makes several ex perimental predictions that can be tested using current techniques. Hippoca mpus 1998;8:651-865. (C) 1998 Wiley-Liss, Inc.