Fimbria/fornix lesions facilitate the learning of a nonspatial response task.

The spatial cognitive map theory of O'Keefe and Nadel (1978) predicts that lesions of the hippocampal system should impair learning on spatial tasks but not learning on nonspatial tasks. However, there is evidence that such lesions can facilitate learning on certain nonspatial tasks. Their theory does not predict such facilitation. Nevertheless, it is reasonable to expect that animals possessing a spatial cognitive map would have an inherent bias to engage a mapping strategy and thus be at a disadvantage on certain nonspatial tasks in comparison with animals without the mapping capacity and bias. In the present study, fimbria/fornix lesions impaired learning on a spatial task, but actually facilitated learning on a nonspatial task of equal difficulty. Thus, brain lesions that interfere with map functioning can facilitate learning on tasks for which a mapping strategy interferes with task solution. The results require a modification of the spatial cognitive map theory.