Comparison of the effects of entorhinal and retrosplenial cortical lesions on habituation, reaction to spatial and non-spatial changes during object exploration in the rat

This study was aimed at comparing the effects of damage to the entorhinal cortex and retrosplenial cortex on exploration and reaction-to-change in rats. Following habituation to a configuration of objects, a familiar object was displaced therefore producing a spatial change. A non-spatial change was made by substituting a familiar object by a novel object. Both entorhinal cortex lesions and retrosplenial cortex lesions elicited a deficit in the rat's reaction to a spatial change. In addition, rats with entorhinal lesions showed hypoactive object exploration and exhibited a mild deficit in reaction to a non-spatial change. This may reflect the importance of temporal cortical input in object recognition. Overall, these results suggest that the entorhinal cortex and the retrosplenial cortex contribute to the processing of the geometric properties of the environment and have thus close functional links. (C) 2004 Elsevier Inc. All rights reserved.