Fig. 1.

Spatial firing properties of neurons in hippocampus (A; place cell), medial entorhinal cortex (MEC) (B; grid cell), and posterior parietal cortex (PPC) (C). In A and B, the rat runs freely in an open-field environment; in C, the rat traverses a complex maze with multiple segments and turns (Left, path of the animal; Center, rate map with lights on; Right, rate map in darkness). Firing rates are color-coded, with red showing maximal rate and blue minimum (scale bar to the right). Note that the parietal neuron fires at specific epochs along the trajectory and that firing is independent of visual inputs. [C is adapted with permission from ref. 66 (Copyright 2006, Neuron).]