Parietal cortex, navigation, and the construction of arbitrary reference frames for spatial information

The registration of spatial information by neurons of the parietal cortex takes on many forms. In most experiments, spatially modulated parietal activity patterns are found to take as their frame of reference some part of the body such as the retina. However, recent findings obtained in single neuron recordings from both rat and monkey parietal cortex suggest that the frame of reference utilized by parietal cortex may also be abstract or arbitrary in nature. Evidence in rats comes from work indicating that parietal activity in freely behaving rodents is organized according to the space defined by routes taken through an environment. In monkeys, evidence for an object-centered frame of reference has recently been presented. The present work reviews single neuron recording experiments in parietal cortex of freely behaving rats and considers the potential contribution of parietal cortex in solving navigational tasks. It is proposed that parietal cortex, in interaction with the hippocampus, plays a critical role in the selection of the most appropriate route between two points and, in addition, produces a route-based positional signal capable of guiding sensorimotor transitions.