A two-platform task reveals a deficit in the ability of rats to return to the start location in the water maze

The ability of rats to return to the start location was examined with a 4-a rm radial water maze. The task required rats to find 2 hidden platforms in sequence. Rats were released from 1 of 3 arms and there was a platform loca ted in the fourth arm. Once a rat found this platform, a 2nd platform was r aised in another location, which was either the start location, for 1 group , or another fixed location, for a control group. Across 3 experiments, all rats learned the location of the 1st fixed platform in 80 to 120 trials. H owever, rats had difficulty finding a 2nd platform if it was at the start l ocation. Control groups revealed that rats could learn 2 platform locations and that the difficulty in learning to return to the start location did no t seem to be attributable to its aversive nature. In separate groups, expos ure to the start location was increased by starting the rats from an initia lly stable platform. Rats still did not readily learn to return to the star t location. The authors suggest that start location, when varied, cannot re adily be used to define the location of a hidden platform.