Arousal and activity level of rats with lesions in the dorsal hippocampus

The effect on gross locomotor activity of irrelevant stimuli, prior exposure to these stimuli and two dosages of amphetamine were assessed on rats with lesions in the dorsal hippocampus. These animals were significantly more active post-operatively than sham-lesioned subjects. Prior exposure to the irrelevant stimuli increased post-operative differentiation between stimuli, whereas the introduction of amphetamine had the reverse effect. Changes in locomotor activity occurred at lower dosages of amphetamine than in previous studies, suggesting that the irrelevant stimuli have an arousal effect which acts additively with amphetamine and hippocampal impairment.