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The hippocampus and associative parietal cortex (APC) both contribute to spatial memory but the nature of their functional interaction remains unknown. To address this issue, we investigated the effects of APC lesions on hippocampal place cell firing in freely moving rats. Place cells were recorded from APC‐lesioned and control rats as they performed a pellet‐chasing task in a circular arena containing three object cues. During successive recording sessions, cue manipulations including object rotation in the absence of the rat and object removal in the presence of the rat were made to examine the control exerted by the objects or by non‐visual intramaze cues on place field location, respectively. Object rotations resulted in equivalent field rotation for all cells in control rats. In contrast, a fraction of place fields in APC‐lesioned rats did not rotate but remained stable relative to the room. Object removal produced different effects in APC‐lesioned and control rats. In control rats, most place fields remained stable relative to the previous object rotation session, indicating that they were anchored to olfactory and/or idiothetic cues. In APC‐lesioned rats, a majority of place fields shifted back to their initial, standard location, thus suggesting that they relied on uncontrolled background cues to maintain place field stability. These results provide strong evidence that the hippocampus and the APC cooperate in the formation of spatial memory and suggest that the APC is involved in elaboration of a hippocampal map based on proximal landmarks.

Rats with lesions of the entorhinal or parietal cortex were tested in a homing task on a circular platform containing food cups and surrounded by curtains. The animals had to leave a refuge, explore the platform to find a hidden piece of food and carry it back to the refuge. Once the rats were proficient at performing the procedural aspects of the task, they were tested in two successive types of trials in which the food pellet was either always located in the central cup (food at center, “FAC” trials) or placed in a randomly chosen cup (food at random, “FAR” trials). Except in the first FAC trials, all groups displayed similar outward paths in FAC and FAR trials, showing that both types of trials involved equivalent path integration demand. Analysis of the homing accuracy showed that rats with entorhinal cortex or parietal cortex lesions exhibited inaccurate returns to the starting hole, suggesting that these two cortical areas are part of a neural network mediating path integration.

Rodents are able to rely on self-motion (idiothetic) cues and navigate toward a reference place by path integration. The authors tested the effects of dorsal hippocampal and parietal lesions in a homing task to dissociate the respective roles of the hippocampus and the parietal cortex in path integration. Hippocampal rats exhibited a strong deficit in learning the basic task. Parietal rats displayed a performance impairment as a function of the complexity of their outward paths when the food was placed at varying locations. These results suggest that the parietal cortex plays a specific role in path integration and in the processing of idiothetic information, whereas the hippocampus is involved in the calibration of space used by the path integration system.