Thematic role assignment in two severely aphasic patients: associations and dissociations

Two severely aphasic patients were compared in their abilities to comprehend and produce locative prepositional phrases and reversible S-V-O sentences using English and C-VIC, a computer-based iconographic communication system. One patient demonstrated a significant dissociation between his performance in interpreting symbol order in C-VIC prepositional phrases vs. S-V-O sentences. Patients were able to comprehend order in C-VIC S-V-O sentences significantly better than they were able to assign symbol order when they produced these sentences. These data suggest that the procedures for assigning thematic roles to nouns in sentences are at least partially distinct for comprehension and production and that the ordering of nouns around prepositions involves conceptual processes distinct from those involved in ordering nouns around verbs.