Subiculum neurons map the current axis of travel
Travel constrained to paths, a common navigational context, demands knowledge of spatial relationships between routes, their components, and their positioning in the larger environment. During traversal of an environment composed of multiple interconnected paths, a subpopulation of subiculum neurons robustly encoded the animals current axis of travel. The firing of these axis-tuned neurons peaked bimodally at head orientations approximately 180 degrees apart. Track rotation experiments revealed that axis encoding carried the spatial reference frame of the larger environment as opposed to the track itself. However, axis-tuned activity of the same subpopulation was largely absent during unconstrained movement about a circular arena. Thus, during navigation in a path-rich environment, subpopulations of subiculum neurons encode the animals current axis of travel relative to environmental boundaries - providing a powerful mechanism for mapping of specific relationships between routes, route components, and the larger environment.