Grammatical category ambiguity in aphasia.

This study asked whether aphasic adults show different noun/verb retrieval patterns based upon their clinical categorization as fluent or nonfluent. Participants selected either the noun or the verb meaning of target words, as presented in three contexts. The framework was that nouns (associated with temporal lobe function) are processed, stored, and retrieved separately from verbs (associated with frontal lobe function), implying separate status in the mental lexicon. Stimuli were homophonic homographs, words that are spelled and pronounced the same but which have different meanings (in this case, noun and verb meanings). Another contrast was the putative difference between systematic pairs (e.g., "kiss" and "farm"), in which noun and verb meanings are transparently related, and may be stored as a unit, and unsystematic pairs (e.g., "squash" and "sink"), in which noun and verb meanings are apparently unrelated, implying discrete storage. Results demonstrated significant interactions between fluent and nonfluent participants, suggesting that, as expected, fluent aphasic adults have more difficulty with nouns, nonfluent aphasic adults have more difficulty with verbs. There was no effect of systematicity. Contrary to expectations, verbs proved less vulnerable, rather than more vulnerable, to aphasic impairment.