Fig. 1. Egocentric and Allocentric Spatial Correlates in POR.

(A) An example Nissl-stained sagittal section from one rat (PL61) showing the boundaries of POR. Black arrow indicates the border between dorsal and ventral subdivisions of POR. (B) Schematic top-down view of a rat in the recording arena illustrating three measures that together specify a single allocentric location in the environment. The dotted line extending rightward from the rat indicates the reference axis for allocentric head direction tuning; HD measurements increase with counterclockwise rotation of the rat, such that the rat has an allocentric head direction of 0˚ when it is facing ‘east’ (in line with the reference axis) and 90˚ when it is facing ‘north’. Center bearing is calculated as the eccentricity of the environment center from the rat’s heading. The star indicates the location of the environment center. (C) Directional spike plots (gray trace shows animal’s path, dots show spike locations colored by head direction; color bar below) and center-bearing tuning curves for two example cells that encode egocentric bearing of the environment center. (D) Histogram of the preferred bearings of all center-bearing cells recorded in POR. Dotted red line shows a bimodal von mises mixture fit to the histogram, with peaks at 30˚ and 224˚. (E) Directional spike plots and center-distance curves for two example center-distance cells recorded in POR. (F) Directional spike plots and head direction curves for two example head direction cells recorded in POR. (G) A directional spike plot and three tuning curves (center bearing in blue, head direction in red, and center distance in green) for a POR cell tuned conjunctively to head direction and center bearing with a moderate linear response to center distance. Color bar indicates head direction for directional spike plots.