UC San Diego

Auditory sentence processing is astonishingly complex and involves the rapid processing and integration of many different forms of information. While this is seemingly effortless for neurologically unimpaired listeners, it is clear from the literature that brain damage can cause the normal language system to be disrupted in specific and testable ways. One major goal of this dissertation is to describe how the system is fractionated in aphasia by focusing on the time-course of using specific information types that appear to be involved in the unimpaired language system.

A series of sentence processing studies are presented exploring the impact of syntactic structure in neurologically unimpaired listeners and in listeners with Broca’s aphasia (Chapter 3), the impact of thematic fit and prosody in college-age adults (Chapter 4) and individuals with aphasia along with a group of age-matched healthy controls (Chapter 5).

Chapter 2 reviews research on sentence processing, and accounts of the sentence comprehension deficit in aphasia are also discussed. Chapter 3 provides evidence that similarity-based interference, which results from certain syntactic structures, contributes to the sentence comprehension deficit in aphasia. Chapter 4 examines how thematic fit/plausibility and prosody impacted syntactic structure building in college-age adults using event-related potentials (ERPs). Results revealed that the parser was able to use thematic fit/plausibility information to predict upcoming syntactic structure before the critical verb. Syntactic reanalysis was triggered at the critical verb in sentences with incongruent prosody and no plausibility cue. Chapter 5 examined how individuals with Broca’s aphasia and age-matched controls use plausibility and prosodic cues. The results from the age-matched controls were nearly identical to the college-age adults (Chapter 4). However, the group of individuals with aphasia with a less severe comprehension deficit could predict upcoming syntactic structure when provided with a plausibility cue, but without a plausibility cue had difficulty integrating prosody with syntactic structure. Those with a more severe comprehension deficit had difficulty integrating prosodic and lexical-semantic cues with syntactic structure. Thus, similarity-based interference, lexical-semantic processing and prosody are all implicated in the sentence comprehension deficit seen in individuals with Broca’s aphasia.