DECIPHERING THE HIPPOCAMPAL POLYGLOT - THE HIPPOCAMPUS AS A PATH INTEGRATION SYSTEM

Hippocampal 'place' cells and the head-direction cells of the dorsal p resubiculum and related neocortical and thalamic areas appear to be pa rt of a preconfigured network that generates an abstract internal repr esentation of two-dimensional space whose metric is self-motion. It ap pears that viewpoint-specific visual information (e.g. landmarks) beco mes secondarily bound to this structure by associative learning. These associations between landmarks and the preconfigured path integrator serve to set the origin for path integration and to correct for cumula tive error. In the absence of familiar landmarks, or in darkness witho ut a prior spatial reference, the system appears to adopt an initial r eference for path integration independently of external cues. A hypoth esis of how the path integration system may operate at the neuronal le vel is proposed.