Contrasting patterns of comprehension for superordinate, basic-level, and subordinate names in semantic dementia and aphasic stroke patients

Abstract

It is well established that patients with semantic memory impairment show a relative sparing of general superordinate information as compared with more detailed item-specific information. The objective of the current study was to examine whether or not this superordinate superiority effect is also reliably observed in individuals with stroke. The participants were 3 patients with a diagnosis of semantic dementia (SD) and 4 left middle cerebral artery stroke patients. In the first experiment, participants were administered a series of spoken-word–picture matching tasks, in which picture identity was probed under two conditions: item name (e.g., goose, beetle, shark, hedgehog) and superordinate name (e.g., bird, insect, fish, mammal). The SD patients showed the predicted pattern of performance, identifying stimuli significantly more accurately by their superordinate term than by their specific name. By contrast, the stroke patients showed the reverse pattern of inferior performance in the superordinate condition in all versions of the experimental task. In a second experiment comparing comprehension of basic-level names (e.g., dog, bird, fish) and subordinate-level names (e.g., Dalmatian, sparrow, trout), stroke patients also showed a reversal of the normal basic-level effect, showing less accurate comprehension of basic-level names. The pattern of results documented among the stroke patients cannot be accommodated obviously or readily by existing models of conceptual knowledge. These contrasting abilities of SD patients, stroke patients, and normal healthy participants to process subordinate, basic-level, and superordinate names are considered in relation to disorders of executive processing and taxonomic categorization.