Transformation of head-direction signal into spatial code
Head direction (HD), boundary vector, grid and place cells in the entorhinal-hippocampal system form the brains navigational system that allows to identify the animals current location. How the functions of these specialized neuron types are acquired and how their computations relate to each other remain to be understood. Firing patterns of HD neurons are influenced by the ambulatory constraints imposed upon the animal by the boundaries of the explored environment. In the post-subiculum, the main cortical stage of HD signal processing, the amount of spatial information is increased compared to their driving thalamic inputs by the combination of the HD signal with other sensory modalities. In addition, HD signal directly reach the hippocampus, likely conveyed from the thalamus. These findings demonstrate how the HD and other sensory information can be transduced into a spatial code in parallel, distributed pathways.