Interaction of Egocentric and World-Centered Reference Frames in the Rat Posterior Parietal Cortex

Abstract

Navigation requires coordination of egocentric and allocentric spatial reference frames and may involve vectorial computations relative to landmarks. Creation of a representation of target heading relative to landmarks could be accomplished from neurons that encode the conjunction of egocentric landmark bearings with allocentric head direction. Landmark vector representations could then be created by combining these cells with distance encoding cells. Landmark vector cells have been identified in rodent hippocampus. Given remembered vectors at goal locations, it would be possible to use such cells to compute trajectories to hidden goals. To look for the first stage in this process, we assessed parietal cortical neural activity as a function of egocentric cue light location and allocentric head direction in rats running a random sequence to light locations around a circular platform. We identified cells that exhibit the predicted egocentric-byallocentric conjunctive characteristics and anticipate orienting toward the goal.

Decision and navigation in mouse parietal cortex

“…Our results resonate with the view that rodent PPC encodes combinations of spatial attributes (McNaughton et al, 1994;Nitz, 2006Nitz, , 2012Save andPoucet, 2000, 2009;Whitlock et al, 2012;Wilber et al, 2014). Specifically, we found that the activity of PPC neurons can be accurately predicted based on two extremely simple spatial measures: position of the animal along the corridor, and heading direction.…”

“…A complementary set of studies performed in rodents suggested an important role of PPC in spatial navigation (McNaughton et al, 1994;Nitz, 2006Nitz, , 2012Save andPoucet, 2000, 2009;Whitlock et al, 2012;Wilber et al, 2014). Rat PPC encodes combinations of spatial location and body movement (McNaughton et al, 1994;Nitz, 2006Nitz, , 2012Whitlock et al, 2012;Wilber et al, 2014).…”

“…Rat PPC encodes combinations of spatial location and body movement (McNaughton et al, 1994;Nitz, 2006Nitz, , 2012Whitlock et al, 2012;Wilber et al, 2014). Inactivating it, moreover, can impair navigation (Save andPoucet, 2000, 2009).…”

Spatial representation in the hippocampal formation: a history

“…A little more than half of the cells were also place cells, but a substantial fraction did not have any significant tuning to place. Cells with essentially the same characteristics were recently reported in posterior parietal cortex 17 . Goal-vector cells are reminiscent of cells reported in rats in earlier hippocampal studies, in which neural firing increased in the proximity of a goal 73,[221][222][223][224][225] , and the finding of goal-orientation cells in both parietal cortex and hippocampus begs the question of which region is 'copying' which.…”

“…Navigation in an idiothetic reference frame is often referred to as 'path integration' , a process by which animals use self-motion cues (such as motor efference, optical flow, and vestibular information) to keep track of their own location relative to a starting point [11][12][13][14] . Decades of investigation have shown that egocentric space is not represented primarily in the hippocampal formation but rather in parietal cortex and associated regions [15][16][17] . O'Keefe's studies showed from the outset that, instead, place cells encode an animal's location in an Although the study of the cellular and circuit mechanisms of spatial representation in the brain today is centered on the hippocampal and parahippocampal formation, the study of spatial coding did not begin there, but rather began with the parietal cortex, in the form of early observations on patients with parietal damage 1,2 ; in many respects, one takes a risk in attempting to limit the discussion to the hippocampal formation 3 .…”