Head Direction Cells: From Generation to Integration

Abstract

To maintain spatial orientation and guide navigation, an animal must have knowledge of its location and displacement of distance and direction from that location. Cells within the hippocampal formation and connected structures are spatially correlated to location and direction. Specifically, head direction (HD) cells discharge as a function of the directional heading of an animal, independent of their location or behavior. HD cells are found in many brain regions, but the classic circuit involved in generating, updating, and controlling their responses originates in the dorsal tegmental nucleus and projects serially to the lateral mammillary nucleus, anterior thalamic nuclei, and post- and parasubiculum and terminates in the entorhinal cortex. The HD signal is generated by self-movement cues, with the vestibular system playing a critical role. However, HD cells become strongly controlled by environmental cues, particularly visual landmarks. HD cells provide a continuous signal that an animal will use to guide its behavior and maintain orientation. Information provided by HD cells may be critical for generating the grid cell, but not for the place cell signal. Collectively, information from HD, place, and grid cells provide a complete representation of the animal’s orientation in space.