Verb retrieval in aphasia. 2. Relationship to sentence processing.

Sentence comprehension and production were evaluated for 10 chronic aphasic patients who have been shown to demonstrate one of three patterns in the relative case of retrieval of nouns and verbs. Although these patterns of noun/verb production were not entirely predictable from patients' clinical classifications, they were found here to be significantly correlated with several structural indices of sentence production and with failure to comprehend semantically reversible sentences. Noun/ verb retrieval patterns were not strongly correlated with speech fluency nor with morphological characteristics of sentence production. Patients with relative impairment in the production of verbs were found to rely on high frequency, semantically empty, "light" verbs when producing sentences and to favor simple syntactic structures in which verbs do not require inflections. When forced to produce substantive verbs (in picture and scene descriptions), verb retrieval continued to undermine the production of well-formed sentences for the verb-impaired patients. In addition, two of five such patients also showed some evidence of poor realization of noun arguments for verbs they could not produce. Results are interpreted as indicating multiple contribution to patients' sentence processing impairments, one of which may be selective difficulty retrieving verbs.