Altered grid-like coding in early blind people
Spatial navigation in humans relies heavily on vision. However, the impact of early blindness on the brain navigation network and on the hippocampal-entorhinal system supporting cognitive maps, in particular, remains elusive. Here, we tested sighted and early blind individuals in both imagined navigation in fMRI and real-world navigation. During imagined navigation, the Human Navigation Network was reliably activated in both groups, showing resilience to visual deprivation. However, neural geometry analyses highlighted crucial differences between groups. A 60{degrees} rotational symmetry, characteristic of grid-like coding, emerged in the entorhinal cortex of sighted but not blind people, who instead showed a 4-fold (90{degrees}) symmetry. Moreover, higher parietal cortex activity during navigation in the blind was correlated with the magnitude of 4-fold symmetry and real-word navigation abilities. In sum, early blindness can alter the geometry of entorhinal cognitive maps, possibly as a consequence of higher reliance on parietal egocentric coding during navigation.