Double Dissociation Between Perseveration in Memory and Problem Solving Tasks

Abstract

This study reports a double dissociation between perseverative responses on a short-term verbal memory test and a card sorting task, as shown by two patients with cerebral tumours. The two patients were matched for number of correct responses on the memory task. The first patient, with a craniopharyngioma and associated dilatation of the third ventricle and lateral ventricles, showed perseveration on the short-term memory task but not on the card sorting task. The second patient, with a subfrontal tumour involving the anterior corpus callosum, perseverated on the card sorting task but not on the short-term memory task. The presence of this double dissociation demonstrates the functional specificity of perseveration in certain memory and problem solving contexts and suggests that distinct subcortical/frontal mechanisms may underly specific types of perseveration.