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Understanding discourse-linked elements in aphasia: a threefold study in Russian
Background: Agrammatic speakers have problems with grammatical encoding and decoding. However, not all syntactic processes are equally problematic: present time reference, who questions, and reflexives can be processed by narrow syntax alone and are relatively spared compared to past time reference, which questions, and personal pronouns, respectively. The latter need additional access to discourse and information structures to link to their referent outside the clause (Avrutin, 2006). Linguistic processing that requires discourse linking is difficult for agrammatic individuals: verb morphology with reference to the past is more difficult than with reference to the present (Bastiaanse et al., 2011). The same holds for which questions compared to who questions and for pronouns compared to reflexives (Avrutin, 2006). These results have been reported independently for different populations in different languages. The current study, for the first time, tested all conditions within the same population.
Aims: We had two aims with the current study. Firstly, we wanted to investigate whether discourse linking is the common denominator of the deficits in time reference, wh-questions, and object pronouns. Secondly, we aimed to compare the comprehension of discourse-linked elements in people with agrammatic and fluent aphasia, to define the degree of the discourse linking deficit specificity.
Methods & Procedures: Three sentence-picture-matching tasks were administered to 10 agrammatic, 10 fluent aphasic, and 10 non-brain-damaged Russian speakers (NBDs): (1) the Test for Assessing Reference of Time (TART) for present imperfect (reference to present) and past perfect (reference to past), (2) the Wh-Extraction Assessment Tool (WHEAT) for which and who subject questions, and (3) the Reflexive-Pronoun Test (RePro) for reflexive and pronominal reference.
Outcomes & Results: NBDs scored at ceiling and significantly higher than the aphasic participants. We found an overall effect of discourse linking in the TART and WHEAT for the agrammatic speakers, and in all three tests for the fluent speakers. Scores on the RePro were at ceiling.
Conclusions: The problems that individuals with agrammatic and fluent aphasia experience when comprehending sentences that contain verbs with past time reference, which question words and pronouns are caused by the fact that these elements need to involve operations at the discourse level. The effect is not specific to agrammatism, although might result from different underlying disorders in agrammatic and fluent aphasia.