Sentence context effects and the timecourse of lexical ambiguity resolution in nonfluent aphasia

In the current neurolinguistic literature, two proposals have been put forth to account for the deficit in ambiguous word processing observed in nonfluent aphasic patients. One proposal maintains that these individuals are impaired in the selective access of ambiguous word meanings, while the other argues that they are impaired in the process of contextual selection. In the present study, nonfluent aphasic patients and elderly control subjects participated in a semantic priming experiment, in which ambiguous words were presented in different biasing contexts at both a 0- and 750-ms ISI. At both ISIs, control subjects showed context-selective access, in that only contextually appropriate meanings were activated. In contrast, at the 0-ms ISI, the nonfluent aphasic patients showed activation of both meanings of the ambiguous word regardless of context. Only at the 750-ms ISI did they exhibit context-selective access. These results are consistent with the proposal that left hemisphere damage causing nonfluent aphasia results in an impairment in rapidly integrating lexical-semantic information into context.