The hippocampal formation is linked to spatial navigation but direct evidence in primates during active, unconstrained navigation is lacking. Combined with accurate behavioral tracking of eye and head, we record neurons across hippocampal regions in rhesus macaques during free foraging in an open arena. We find that neurons encode a broad spectrum of spatial variables beyond place fields. Most neurons show mixed selectivity, with diverse representations covering the entire space. The allocentric representations are dominated by facing location and tilt orientation, and a rather low fraction of neurons shows place or grid fields. Spatial facing selectivity mainly reflects head-, rather than gaze-related, properties. These findings reveal that the macaque hippocampal formation represents space using a multiplexed code, with heading properties dominating over simple place coding during free behavior.
bioRxiv Subject Collection: Neuroscience