Water maze learning in rats with neocortical and hippocampal lesions

Experiments were carried out in order to determine whether groups of rats (N = 7) with unilateral or bilateral ablation of the neocortex or with removal of the neocortex plus the hippocampus of either hemisphere could learn to escape from a tank of water (57 cm in diameter) climbing a visible platform when trained for 6 consecutive days. Comparison of the swimming escape latencies among groups showed no statistically significant differences, although over the first four trial blocks the decorticate group was slower (77.19 +/- 39.31, 52.45 +/- 32.37, 31.18 +/- 13.62 and 15.74 +/- 10.94 s, respectively) than the other groups, whose latencies ranged from about 70 s (the longest in the first trial block) to 8 s (the longest in the fourth trial block). Nevertheless, hemi- and bilaterally decorticate rats were still able to learn the water maze task. The same was observed for hemidecorticate plus hemihippocampectomized rats. These results indicate that the neocortex, and the hippocampus in the absence of the neocortex, is not essential for spatial localization using a cue-learning strategy.