Hippocampal Damage Causes Retrograde Amnesia and Slower Acquisition of a Cue-Place Discrimination in a Concurrent Cue-Place Water Task in Rats

Abstract

Explanations of memory-guided navigation in rodents typically suggest that cue- and place-based navigations are independent aspects of behavior and neurobiology. The results of many experiments show that hippocampal damage causes both anterograde and retrograde amnesia (AA; RA) for place memory, but only RA for cue memory. In the present experiments, we used a concurrent cue-place water task (CWT) to study the effects of hippocampal damage before or after training on cue- and place-guided navigation, and how cue and place memory interact in damaged and control rats. We found that damaging the hippocampus before training caused a delay in the expression of cue-place navigation strategies relative to intact control animals; surprisingly, place navigation strategies emerged following pre-training hippocampal damage. With additional training, both control and damaged rats used local cues to navigate in the CWT. Damaged animals also show minor impairments in latency to navigate to the correct cue following a cue contingency reversal. By contrast to these anterograde effects, damage made after training causes RA for cue choice accuracy and latency to navigate to the correct cue. In addition, the extent of hippocampal damage predicted impairments in choice accuracy when lesions were made after training. These data extend previous work on the role of the hippocampus in cue and place memory-guided navigation, and show that the hippocampus plays an important role in both aspects of memory and navigation when present during the learning experience.