Time reference decoupled from tense in agrammatic and fluent aphasia

Background: Reference to an event's time frame can be accomplished through verb inflection. In agrammatic aphasia, a deficit in past time reference has been identified by Bastiaanse and colleagues (2011). In fluent aphasia, specific problems with this time frame (expressed by the past tense) have been found as well (Dragoy & Bastiaanse, 2013; Jonkers & de Bruin, 2009). However, time reference does not always coincide with tense; in languages such as Dutch and English, reference to the past can be established by using past tense (e.g., "he wrote a letter") or a present tense auxiliary in combination with a participle, i.e., the present perfect (e.g., "he has written a letter"). Aims: The goal of this study is twofold. First, it aims to untangle tense problems from problems with past time reference through verb morphology in people with aphasia. Second, this study aims to compare the production of time reference inflection by people with agrammatic and fluent aphasia. Methods & Procedures: A sentence completion task was used to elicit reference to the non-past and past in Dutch. Reference to the past was tested through (1) a simple verb in past tense and (2) a verb complex with an auxiliary in present tense + participle (the present perfect). Reference to the non-past was tested through a simple verb in present tense. Fourteen agrammatic aphasic speakers, sixteen fluent aphasic speakers, and twenty non-brain-damaged speakers (NBDs) took part in this study. Data were analysed quantitatively and qualitatively. Outcomes & Results: NBDs scored at ceiling and significantly higher than the aphasic participants. Agrammatic speakers performed worse than fluent speakers, but the pattern of performance in both aphasic groups was similar. Reference to the past through past tense and [present tense auxiliary + participle] was more impaired than reference to the non-past. An error analysis revealed differences between the two groups. Conclusions: People with agrammatic and fluent aphasia experience problems with expressing reference to the past through verb inflection. This past time reference deficit is irrespective of the tense employed. The error patterns between the two groups reveal different underlying problems