Landmark control and updating of self-movement cues are largely maintained in head direction cells after lesions of the posterior parietal cortex

Head direction (HD) cells discharge as a function of the rat's directional orientation with respect to its environment. Because animals with posterior parietal cortex (PPC) lesions exhibit spatial and navigational deficits, and the PPC is indirectly connected to areas containing HD cells, we determined the effects of bilateral PPC lesions on HD cells recorded in the anterodorsal thalamus. HD cells from lesioned animals had similar firing properties compared to controls and their preferred firing directions shifted a corresponding amount following rotation of the major visual landmark. Because animals were not exposed to the visual landmark until after surgical recovery, these results provide evidence that the PPC is not necessary for visual landmark control or the establishment of landmark stability. Further, cells from lesioned animals maintained a stable preferred firing direction when they foraged in the dark and were only slightly less stable than controls when they self-locomoted into a novel enclosure. These findings suggest that PPC does not play a major role in the use of landmark and self-movement cues in updating the HD cell signal, or in its generation.