Modulation of the impairment of hippocampectomized rats on the radial-arm maze cue task by visual characteristics and subicular damage.

Rats with N-methyl-D-aspartate lesions of the hippocampus that partially damaged the subiculum and controls were trained on 2 versions of the radial-arm maze cue task, with either proximal or distal visual stimuli. In Experiment 1, the relative positions of the stimuli varied across trials. Lesioned rats were impaired when trained on the distal version, as opposed to transiently slowed down when trained on the proximal version. In Experiment 2, the relative positions of the stimuli were fixed throughout training. Lesioned rats were impaired when trained on the distal or the proximal version. Further analyses showed that combined damage to the hippocampus and the subiculum was required to impair performance in the proximal, but not the distal, version.