The spatial parameters encoded by hamsters during exploration: a further study.

The information used by hamsters while reacting to a spatial change after habituation of exploration was analysed. In our previous work, animals had the opportunity to explore a circular open field containing four different objects, for two sessions. During the third session, when the locations of two objects were exchanged, hamsters re-explored selectively the exchanged objects. The present study, relying on the same procedure, examined the possibility that subjects' detection of the change relied on an egocentric strategy, i.e., that hamsters were using the pattern formed by the horizontal alignment of the objects as seen from the location at which they were introduced into the field. Therefore, in Experiment 1, the placement of the subjects at the beginning of the test session was different from that used on previous sessions. Most hamsters still displayed a reaction to the object displacements, although their reactions were not selectively directed to the exchanged objects. Experiment 2 revealed that, when the subjects were placed at a different location at the beginning of each session, the change in object locations was not detected. Lastly, Experiment 3 showed that removing the only available extra-apparatus visual cue did not prevent hamsters from selectively reacting to the displaced objects. These results are discussed with respect to the notion that during exploration hamsters encode local views of the environment, which ultimately leads to the building up of overall cognitive maps after they have been given sufficient exploration.