Rats with hippocampal damage are impaired on place learning in the water task when overtrained under constrained conditions

To date, numerous investigations have been conducted on the mammalian hippo campus to determine its precise function. This research has implicated a fu ndamental role for the hippocampus in the formation of a spatial map that a n animal can use to appropriately guide behavior in complex relational task s. Despite substantial evidence to support this view, there have been chall enges to this theory of hippocampal function. One alternative view suggests that the hippocampus is involved with the integration and updating of volu ntary movement. Therefore, any impairments expressed by rats with hippocamp al damage are not due to the inability to form or use a spatial map, but ra ther arise because they are unable to accurately control and monitor on-lin e movement. Accordingly, investigators, supporting the latter, claim that a nimals with hippocampal lesions are able to solve a spatial version of the water task if they are given explicit training on how to get to the hidden platform. In the present study we trained rodents with or without hippocamp al damage on a cue/place water task for 40 days. In using behaviorally cons training procedures and by overtraining these animals, we provided them wit h knowledge of how to get to the hidden platform, and ensured enough time t o learn the task. Our findings revealed that although rats with hippocampal lesions showed some place responses, they were significantly impaired on a ll measures of place learning compared to sham animals under these intensiv e procedures. Overall, the results of the present study do not support the idea that the hippocampus is not specifically involved in acquisition of pl ace information in the water task. (C) 2000 Wiley-Liss, Inc.