Place navigation in rats guided by a vestibular and kinesthetic orienting gradient.

The role of the slope of terrain in orientation was examined in rats trained to find, among 4 equidistant feeders, the 1 located in the upper left quadrant of a 10% tilted arena (1-m radius). Rats started from the center in light and with randomly changing slope direction reached the correct goal in 90% of 1st choices after 29 sessions. The same rats maintained 83% correct choices when the experiment was conducted in darkness. On a horizontal arena, their performance became random. After training, successful navigation was also observed (71% correct 1st choices) when the rats were started from different points at about 30 cm from the wall. This finding suggests that the slope of terrain may be used to establish a cognitive map based primarily on kinesthetic and vestibular signals. The flexibility of such a map seems to be rather limited, however, because changing the goal position with respect to inclination requires prolonged retraining.