Reconstructing from a degraded trace: a study of sentence repetition in agrammatism

Six agrammatic aphasics repeated simple active and passive voice sentences, varying in degree of semantic constraint: plausible, reversible, and implausible. Frequency of correct response was not sensitive to this semantic manipulation, but error pattern was. In general, errors to plausible targets consisted of relatively inconsequential transformation of the open or closed class vocabulary, while errors to implausible targets implicated a change of syntactic voice. In making these errors, the patients displayed evidence of productive control of the passive morphology and a degree of sensitivity to the syntactic and thematic consequences consequences of passive voice. The repetition errors did not transform the surface order of the major lexical items. The results are interpreted as evidence for a sentence memory trace that preserves, minimally, the major grammatical roles of the target sentence and that serves as input to a reconstructive process that is biased toward the production of semantically plausible sentences.