Human Electrocortical Dynamics of Spatial Navigation in a Predefined Square Spiral

Low frequency neural oscillations in animals have been shown to play an important role in spatial navigation. However, such studies in humans have remained largely unexplored. We recorded electroencephalogy (EEG) and full body movement as subjects (n=4) walked at two different speeds (slow and fast) in a 4mx4m square spiral track. We then projected subjects' moment-to-moment EEG onto their spatial paths, separately for each outward and inward traversal of the track. Analysis of the EEG dynamics over space showed that the Hilbert envelope (power) of delta/low theta (2-5 Hz) oscillations over midline posterior, parietal cortex (electrode Pz) was locked in space to the relative position of the subject along each arm of the square spiral. There was a change in the envelope from the first third to the last third of each path, irrespective of path size, orientation or direction. The degree of spatial locking was modulated by walking speed, being much greater for fast than for slow speeds. However, the envelope activity itself was not a simple consequence of speed variation within a condition, since projecting moment-to-moment speed on each path produced a very different pattern than did projecting delta/low theta power. These results serve as novel evidence of neural oscillations, as detectable by EEG, in modulating spatial navigation of freely moving humans in open space.