Three-dimensional spatial selectivity of hippocampal neurons during space flight

‘Place’ cells of the hippocampus and ‘head-direction’ (HD) cells of the thalamus and limbic cortex derive their spatial and directional specificity from a combination of idiothetic (self-motion) cues and external landmarks, which normally reinforce each other to generate a robust neural code for location and direction1. In weightlessness, however, three-dimensional navigation can cause the idiothetic and landmark cues to conflict. Nonetheless, neural recordings on the space shuttle demonstrated that the hippocampus can create a robust spatial code for three orthogonal surfaces in the weightless environment of space flight.