Comprehension of reversible sentences in aphasia: the effects of verb meaning.

Comprehension of semantically reversible active and passive voice sentences was tested in a timed sentence/picture verification task. Three sets of six verbs were identified that incorporated different features of meaning relevant to the assignment of nouns to the thematic role of agent. Normal control subjects showed an effect of verb set on their response times, with significant effects between sets in the predicted direction. A group of aphasic patients without sentence comprehension disorder also showed a significant effect of verb set despite long and variable response times. A group of patients with reversible comprehension disorder in screening tasks showed weaker effects, primarily because of the use of consistent response biases that ignored the sentence verb. An experimental treatment of active/passive comprehension was conducted with two of these latter patients; one patient reached ceiling in post-testing, and the other showed significant improvement but demonstrated residual comprehension problems that indicated differences across verb sets. Results support the critical importance of verb meaning to normal and aphasic sentence comprehension.