The formation of cognitive maps of adjacent environments: evidence from the head direction cell system.

In 2 experiments the authors tested whether the head direction (HD) cell system underlies a sense of direction maintained across environments. In Experiment 1, HD neurons failed to maintain their firing directions across T mazes in adjacent environments but rather reoriented to the T maze within each environment. Such reorientation suggests that familiar landmarks override an internal directional sense, so in Experiment 2 the authors recorded HD neurons as rats walked between novel and familiar "rooms" of a 4-chamber apparatus. In novel rooms, HD neurons maintained the firing direction of the preceding environment. However, in familiar rooms, HD neuron firing directions shifted to agree with the landmarks therein. With repeated experience, a homogeneous representation of all rooms developed in a subset of the rats.