Spatial memory in rats with lesions to the region of the mammillary bodies

The objective of this investigation was to determine whether lesions to the region of the mammillary bodies of rats impair performance on various learning and memory tasks. It was demonstrated that such lesions are sufficient to impair performance on tasks that require memory for spatial information. Deficits were found in both working and reference memory paradigms, with more severe impairments in the former. Ability to discriminate spatial location was not affected when delay was minimal, but retention was progressively impaired as delay was increased. A dissociation in the effect of the lesions on performance of analogous spatial and nonspatial tasks was observed. The lesions did not impair the learning of a visual discrimination/reversal, or a conditioned taste aversion. It is concluded that lesions to the region of the mammillary bodies have a selective effect on spatial learning and memory. The relevance of these findings to Korsakoff's psychosis is discussed