Verb production in the nonfluent and semantic variants of primary progressive aphasia: The influence of lexical and semantic factors

Differential patterns of impairment with respect to noun and verb production have been observed in the nonfluent and semantic variants of primary progressive aphasia. However, the factors influencing this discrepancy remain unclear. The present study evaluates verb retrieval in primary progressive aphasia using a naming task and a story completion task. Findings indicate that patients with the semantic variant are influenced by familiarity, frequency, and age of acquisition in both object and action naming, whereas patients with the nonfluent variant are not. Surprisingly, there were no differences in either group between object and action naming, presumably because the lists were well matched on pertinent variables. In the story completion task, greater impairment in semantically heavier than in semantically lighter verbs was observed for the semantic variant, and grammaticality and verb tense agreement was significantly lower in the nonfluent variant. The present findings suggest that lexicosemantic attributes affect verb production in the semantic variant, whereas both lexicosemantic and syntactic attributes affect verb production in the nonfluent variant.