Place learning in hippocampal rats and the path integration hypothesis.

Although two decades of research suggests that the hippocampus plays a special role in place learning, the present paper describes a series of studies using swimming pool spatial tasks that show that hippocampal rats have considerable place learning ability, which includes the abilities of finding, remembering, and searching for places. The same studies also show that when environmental cues are uninformative, as is the case early in original learning and again in reversal learning, hippocampal rats are impaired. Since control rats quickly resolve spatial ambiguity in these situations, it is argued that they must have a system with which they can calibrate spatial cues. The discussion considers the possibility that they use dead reckoning with path integration, a spatial strategy that provides guidance based on cues generated by a point of reference and subsequent self-movement and not the cues in the environment through which they are moving. With path integration an animal can monitor its location and at the same time attach spatial meaning to cues that it encounters. An ability to recalibrate external cues may provide the tuning that allows control rats to quickly acquire place responses while hippocampal rats are constrained by the processes of associative learning.