Latent attractors: A model for context-dependent place representations in the hippocampus

Cells throughout the rodent hippocampal system show place-specific patterns of firing called place fields, creating a coarse-coded representation of l ocation. The dependencies of this place code-or cognitive map-on sensory cu es have been investigated extensively, and several computational models hav e been developed to explain them. However, place representations also exhib it strong dependence on spatial and behavioral context, and identical senso ry environments can produce very different place codes in different situati ons. Several recent studies have proposed models for the computational basi s of this phenomenon, but it is still not completely understood. In this ar ticle, we present a very simple connectionist model for producing context-d ependent place representations in the hippocampus. We propose that context dependence arises in the dentate gyrus-hilus (DGH) system, which functions as a dynamic selector, disposing a small group of granule and pyramidal cel ls to fire in response to afferent stimulus while depressing the rest. It i s hypothesized that the DGH system dynamics has "latent attractors," which are unmasked by the afferent input and channel system activity into subpopu lations of cells in the DG, CA3, and other hippocampal regions as observed experimentally. The proposed model shows that a minimally structured hippoc ampus-like system can robustly produce context-dependent place codes with r ealistic attributes.