An independent, landmark-dominated head-direction signal in dysgranular retrosplenial cortex

The authors report on a subpopulation of neurons in retrosplenial cortex that is more sensitive to head direction in a local, visually defined reference frame than to global head direction. These neurons may be the means by which visual landmark information can influence the overall sense of direction. We investigated how landmarks influence the brain's computation of head direction and found that in a bidirectionally symmetrical environment, some neurons in dysgranular retrosplenial cortex showed bidirectional firing patterns. This indicates dominance of neural activity by local environmental cues even when these conflicted with the global head direction signal. It suggests a mechanism for associating landmarks to or dissociating them from the head direction signal, according to their directional stability and/or utility.