Patterns of comprehension and production of nouns and verbs in agrammatism: Implications for lexical organization

This study examined the relationship between verb retrieval and verb-argument structure properties in seven agrammatic aphasic patients using tasks requiring access to the verb's lexicon fur both comprehension- and productionlike processes. Results showed intact comprehension of bath nouns and verbs and noun naming, but impaired naming of verbs. Subjects also demonstrated near-normal performance on a grammaticality judgment tusk involving verb-argument-structure violations but were impaired in categorizing, verbs by type (based on number of obligatory arguments). In both naming and categorization conditions, a hierarchy of verb difficulty emerged. Subjects were more accurate in naming/categorizing one-place verbs than two-place verbs and more accurate in naming/categorizing two-place verbs than three-place verbs. The pattern of selective impairment in lexical access/retrieval supports the hypothesis th;lt one dimension of normal lexical organization is by form class. The results also suggest that no necessary relationship exists between production difficulties and comprehension of nouns/verbs in agrammatism. Further, thr performance pattern noted supports the claim that verb-argument-structure properties, an important component of the verb lexicon, influence verb production at the single-word and at the sentence level. Subjects' performance on different tasks suggests that the locus of breakdown in the verb-retrieval processes for productionlike tasks may be in accessing information at the lemma level of representation as per Beck's model (1995) of sentence production. (C) 2000 Academic Press.