The effects of parietal cortex lesions on an object/spatial location paired-associate task in rats

Abstract

The present experiment was conducted in order to test the hypotheses (1) that the posterior parietal cortex (PPC) serves as a neural system that is critical for binding spatial location and object information in long-term memory and (2) that even restricted lesions of the PPC would result in similar deficits. Long-Evans rats were given either a large or a small PPC lesion or a control surgery under Nembutal anesthesia. After a 1-week recovery period, the rats were tested on either an object or a spatial location go/no-go successive discrimination task. After reaching criterion (a minimum of a 5 sec difference between reward and nonreward trials), they were trained on the other discrimination. After reaching criterion on the second discrimination, all of the rats were trained on a successive discrimination go/no-go task in which they had to remember which object/spatial location pairs had been associated with reward. As compared with controls, neither the small nor the large PPC lesion impaired object or spatial location discrimination. In the paired-associate object/spatial location task, both large and small PPC lesioned rats were impaired, relative to controls. These data suggest that the rodent PPC is not involved in object or spatial location discrimination but rather is involved in discrimination and long-term memory for the combination of object and spatial location information.