Assessing the elements contributing to a "mapping" deficit: a targeted treatment study.

Aphasic patients with excellent comprehension of word meanings frequently fail to understand simple declarative sentences in which either of two nouns could reasonably serve as agent of a transitive action. This study employed targeted treatment of this comprehension problem in a chronic aphasic patient (E.A.) in an attempt to isolate the source or sources of his comprehension failure. Treatment exercises that relied on error feedback in sentence-picture matching or verification initially were not effective. Comprehension of active and passive sentences improved only after both structures were explicitly compared and linked to a picture. Subsequently E.A. maintained consistently accurate interpretation of both sentence types in the treatment exercises as long as the full sentence was available to him. E.A. learned to assign thematic roles using a limited set of cues in the surface structure. Although improvement was reported in untreated sentences, the degree of generalization and the level of performance differed across tasks and appeared to be attributable to cognitive impairments that were not addressed by the treatment. Results are interpreted as evidence suggesting that multiple impairments contribute to failure of sentence comprehension tasks.