Poster C79, Sunday, March 26, 5:00 – 7:00 pm, Pacific Concourse
Effective Connectivity of Aphasic Bilingual Semantic Processing
Robert Buckshaw II1, Erin Meier1, Swathi Kiran1; 1Boston University
Making semantic decisions involves low level (bottom-up) processing (mediated by inferior temporal, middle temporal, and angular gyri) and higher level (top-down) cognitive control processes (mediated by inferior, middle, and superior frontal gyri). It is also known that bilingual individuals need to additional cognitive control mechanisms to suppress one language when using the other for such tasks. However, it is unknown how left hemisphere damage impacts language network connectivity in bilingual speakers. In the present study, fMRI and Dynamic Causal Modeling (DCM) were used to investigate how effective connectivity of semantic networks differs between Spanish-English bilingual adults with aphasia (BAA) and healthy, age-matched bilingual controls (BHC). Specifically, Bayesian Model Selection (BMS) was used to determine if participants’ networks differed according to top-down versus bottom-up processing preference and network lateralization (left, right, or bilateral). Four BAA and four BHC completed a semantic word triplet judgment fMRI task in both languages, and both conditions of interest (i.e., Spanish Semantic, English Semantic) were used in DCM. For controls, group-level results indicated no preference for bottom-up or top-down processing for English but a strong preference for top-down processing for Spanish. Best-fit models for controls were primarily left-lateralized for English and bilateral for Spanish. Single-subject BMS in patients indicated that model fit differed from controls but varied from patient to patient in terms of top-down versus bottom-up processing and lateralization. In conclusion, healthy Spanish-English bilinguals have a clear pattern for semantic processing including a pertinent cognitive control aspect for Spanish, and post-stroke this pattern is diminished.
Topic Area: LANGUAGE: Semantic