Fig. 1: The star-maze and spatial selectivity in posterior parietal and hippocampal neurons.

a Main steps of the navigation task performed by animals during the recordings, with corresponding points of view below: (1) the trial began from the extremity of one of the four inbound paths of the star-maze (purple); (2) the animal pushed the joystick to move the camera and reach the maze center; (3) in the center, they pushed the joystick left or right as desired, and then chose an exit path by pushing it forward; (4) if animals chose the correct path (red), they obtained a liquid reward; (5) next, the animal was passively moved to the next starting position through the outbound paths (grey dashed lines), via automatic camera rotation and translation, and the next trial began. During the whole session, the first-person view of the scene (bottom panels schematics of the view) was uninterrupted between trials. Five landmarks placed between the inbound paths provided the only visual cues for orientation, since nothing was directly indicating the reward position. The task was presented on a large 152 × 114 cm screen using a projector, with a horizontal FOV of 74°. Stereopsis was obtained via a pair of shutter glasses synchronized with the projector. b–g Heat maps of the firing rate of single unit examples of PPC neurons, as a function of monkey’s position into the star-maze (i.e. “neural place maps”). The color axis represents the firing rate (maximal firing rate, in spikes/sec, indicated on the top left of each map). All cells had a significant position information content (IC). For a better visualization, data are displayed from the 5th (dark blue; see color bar on the bottom) to the 99th percentiles (bright yellow). The white arrows indicate the direction of camera movements in each maze segment. h–m Same conventions as for b–g, for HPC example cells. All cells had a significant position information content (IC). Figure 1a adapted from Wirth S, et al. Gaze-informed, task-situated representation of space in primate hippocampus during virtual navigation. PLOS Biology, 15: e2001045 (2017) under a CC BY license: https://creativecommons.org/licenses/by/4.0/.