Summary
The hippocampal-parahippocampal formation has long been regarded as the only site for the brain’s navigational system. Nevertheless, studies from patients with medial temporal lobe (MTL) lesions suggest that the hippocampal formation is not essential for space memory, indicating that spatial navigation might be computed with another unknown representation system outside the MTL. Such an extra-hippocampal navigational system has never been identified, however. Here we report the existence, in the rat somatosensory cortex only, of a novel navigational system, which contains the full spectrum of all distinct spatial cell types including place, head-direction, border/boundary, conjunctive, speed and grid cells. All somatosensory spatial cells show similar firing characteristics to those detected previously in the hippocampal-parahippocampal structures. The somatosensory navigational system extends the classical theory of a cognitive map from two discrete hippocampal-entorhinal regions to only one neocortical domain, providing possible alternative and more sophisticated computational algorithms for spatial memory and cognitive mapping.