Population coding by place cells and grid cells

Abstract

Place cells and grid cells are two classes of neurons with spatially selective firing patterns recorded in awake, behaving animals (O’Keefe and Dostrovsky, 1971; Hafting et al., 2005). The majority of principal cells in the rodent hippocampal formation are place cells, while grid cells are found throughout the parahippocampal cortices (Figure 14.1). A smaller fraction of spatially selective cells is found in corresponding brain regions of primates (Rolls et al., 1997; Ekstrom et al., 2003). Spatially selective cells typically fire a train of action potentials whenever an animal passes through one or more subareas within larger two-dimensional (2D) areas, and the cells are silent in other subareas. Each spatially contiguous area of heightened neuronal activity is referred to as a firing field or a place field. Place cells have single or few firing fields, while grid cells have multiple, regularly arranged firing fields. These two cell types, along with the other types of spatially and directionally selective cells that are described in this chapter, are thought to make up the neuronal code for space and to play a key role in the neuronal coding for memory.