Research reportLesions of the hippocampus or dorsolateral striatum disrupt distinct aspects of spatial navigation strategies based on proximal and distal information in a cued variant of the Morris water task

- Rats with hippocampus or striatum lesions were tested in the Morris water task.
- Moment-to-moment swim behavior was analyzed during shifts in swim behavior.
- Initial trajectories and directional responding required hippocampal activity.
- Subsequent swim behavior was guided by the dorsolateral striatum.
- Behavioral shifts within trials appear to be related to shifts between brain areas.

The hippocampus and dorsolateral striatum are critically involved in spatial navigation based on extra-maze and intra-maze cues, respectively. Previous reports from our laboratory suggest that behavior in the Morris water task may be guided by both cue types, and rats appear to switch from extra-pool to intra-pool cues to guide navigation in a sequential manner within a given trial. In two experiments, rats with hippocampal or dorsolateral striatal lesions were trained and tested in water task paradigms that involved translation and removal of a cued platform within the pool and translations of the pool itself with respect to the extra-pool cue reference frame. In the first experiment, moment-to-moment analyses of swim behavior indicate that hippocampal lesions disrupt initial trajectories based on extra-pool cues at the beginning of the trial, while dorsolateral striatal lesions disrupt subsequent swim trajectories based on the location of the cued platform at the end of the trial. In the second experiment, lesions of the hippocampus, but not the dorsolateral striatum, impaired directional responding in situations where the pool was shifted within the extra-pool cue array. These results are important for understanding the cooperative interactions between the hippocampus and dorsolateral striatum in spatial learning and memory and establish that these brain areas are continuously involved in goal-directed spatial navigation. These results also highlight the importance of the hippocampus in directional responding in addition to place navigation.