The Auditory Comprehension of Unaccusative Verbs in Aphasia

Sullivan, Natalie and MacKenzie, Shannon and Walenski, Matthew and Love, Tracy and Shapiro, Lewis P. (2014) The Auditory Comprehension of Unaccusative Verbs in Aphasia. [Clinical Aphasiology Paper]

PDF 567-1115-1-RV(Sullivan-MacKenzie-Walenski).pdf Download (112kB)

Abstract

Some persons with aphasia, particularly those diagnosed with a Broca’s aphasia, exhibit a delayed time course of lexical activation in canonically ordered S-V-O sentences (Ferrill et al., 2012) and delayed re-activation of displaced arguments in sentences that contain syntactic dependencies (Love et al., 2008). These patterns support the Delayed Lexical Activation (DLA) hypothesis: Lexical activation is delayed relative to the normal case, and thus lexical activation and syntactic operations are de-synchronized; that is, lexical access is too slow for normally fast-acting syntactic operations. This delay in lexical access leads to what appear to be syntactic comprehension deficits in aphasia. In the current study we further examined lexical activation during sentence comprehension in persons with aphasia by using unaccusative verbs. Unaccusative verbs are a type of intransitive verb with a single argument that is base generated in object position and displaced to the surface subject position, leaving behind a copy or trace (‘gap’) of the movement (see, for example, Burzio, 1986), as in: 1. The girl vanished <the girl> Thus there is a syntactic dependency between the two positions. When encountering sentences that contain syntactic dependencies (e.g., object relatives, Wh-questions) neurologically unimpaired individuals immediately reactivate the displaced argument at the gap (Shapiro et al., 1999; Love et al., 2008). In contrast to this immediate reactivation, prior findings indicate that neurologically unimpaired individuals do not reactivate the displaced argument in similar sentences with unaccusative verbs until 750ms downstream from the gap (Friedmann et al., 2008). This built-in delay observed with unaccusative verbs in neurologically healthy participants provides a unique opportunity to further examine lexical delays in individuals with Broca’s aphasia. Importantly, individuals with Broca’s aphasia may have unaccusative verb deficits. Previous research has found that persons with aphasia have difficulty producing unaccusative verbs. Offline truth-value judgment tasks with intransitive sentences containing unaccusative verbs do not reveal comprehension deficits (Lee & Thompson, 2004). However, in a sentence-picture matching task, McAllister et al. (2009) found lower accuracy for intransitive sentences that contained unaccusative verbs than transitive sentences. We entertain the following hypothesis: The delayed lexical access routines better synchronize with the delay of reactivating the argument of unaccusatives, suggesting that individuals with Broca’s aphasia should evince a pattern like that of unimpaired individuals. Alternatively, participants with Broca’s aphasia might show activation even further downstream from the gap, given that in other sentence constructions containing syntactic dependencies they exhibit a delayed pattern of reactivation compared to neurologically unimpaired individuals.

Actions (login required)

View Item