Similar development of cued and learned home bases in control and hippocampal-damaged rats in an open field...

Spatial behavior was examined in control rats and rats with neurotoxic-induced damage of the hippocampus in an open field "exploratory" task. In Experiment 1, rats were placed on a large circular table for 30 min for four consecutive days with a short wall adjacent to the table and a large black box near the edge of the table diametrically opposite to the wall. On the fifth day, rats were given a probe test during which both cues were removed. Over the training exposures both control and hippocampal-damaged rats formed "home bases," operationally defined as places where the rats preferentially stopped and spent time, near the cues. When the cues were removed on the probe day, both groups visited, stopped near, and spent time at places adjacent to the cues' previous location. In Experiment 2, rats were given a similar training protocol, but only a single cue was used, which was a small box placed directly on the table that did not block visibility of the entire room. On the fifth day, the box was moved to the other end of the table. Despite the presence of a cued home base, control and hippocampal-damaged rats remembered the original location of the home base. The results are discussed in relation to the comparative task demands of formal and informal test procedures and with respect to their relevance to understanding the neural basis of spatial behavior.