P ( I , J )

Abstract

The cortical circuit for spatial representation has multiple functionally distinct components, each dedicated to a highly specific aspect of spatial processing. The circuit includes place cells in the hippocampus as well as grid cells, head direction cells and border cells in the medial entorhinal cortex. In this review we discuss the functional organization of the hippocampal-entorhinal space circuit. We shall review data suggesting that the circuit of grid cells has a modular organization and we will discuss principles by which individual modules of grid cells interact with geometric features of the external environment. We shall argue that the modular organization of the grid-cell system may be instrumental in memory orthogonalization in place cells in the hippocampus. Taken together, these examples illustrate a brain system that performs computations at the highest level, yet remains one of the cortical circuits with the best readout for experimental analysis and intervention.