Many people with aphasia have difficulty with both language and executive functions. But the relationship between the two types of impairments is not well understood. Both language and executive functions are made up of multiple abilities. Precise, theory-driven approaches are needed to identify how particular executive functions impact particular processes within language. This project will focus on sentence comprehension, which is often impaired in aphasia and affects patients' communicative functions. Correctly understanding sentences requires the parser to resolve conflict between alternative interpretations indicated by different lexical, semantic, and syntactic cues. The proposed research will test the hypothesis that cognitive control, a type of executive function used to resolve conflict between mental representations, plays an important role in sentence comprehension by helping choose between competing interpretations. Healthy adults and patients with aphasia will be tested using a combination of behavioral and functional imaging techniques. Large case series as well as detailed case studies of patients will be used to establish how cognitive control impairments affect sentence comprehension in aphasia. Studies 1, 2 and 3 will determine the impact of cognitive control on the comprehension of sentences containing conflicting cues (Specific Aim 1). Study 1 will address this aim using regression in a case series of patients with diverse aphasia profiles. It will use behavioral measures to evaluate whether patients' performance in general cognitive control tasks predicts their comprehension of ?conflict? sentences. Study 2 will use online eyetracking and electrophysiological (ERP) measures to establish the effect of cognitive control impairments on the detection and resolution of conflict during real-time sentence processing. Study 3 will involve case studies of selected agrammatic patients. It will compare agrammatic patients with and without cognitive control deficits to test the prediction that the former group will be selectively more impaired in conflict sentence comprehension. Studies 4 and 5 will expand the inquiry to the comprehension of noncanonical sentences without conflicting cues (Specific Aim 2). Even in cases where cues to interpretation do not conflict, the use of canonical parsing heuristics can lead to ?garden-path? interpretations that have to be revised. Study 4 will use neuroimaging (fMRI) and within-subject co-localization in healthy adults to test whether noncanonical sentences rely on the same cognitive control networks as conflict sentences. Study 5 will use case studies of selected patients with and without cognitive control deficits to test whether cognitive control impacts recovery from garden-paths during noncanonical sentence comprehension in aphasia. Together, the studies will improve understanding of sentence processing in aphasia and in healthy adults. By clarifying the role of cognitive control in sentence comprehension, they will address questions about how cognitive impairments affect language in aphasia.
This project tests how cognitive control affects sentence comprehension in healthy adults and patients with aphasia. The results will clarify how cognitive deficits outside of language comprehension impact patients' ability to interpret sentences. This can guide future research on alternative ways to treat language and communication disorders.
