The goal of this project is to improve our understanding of the cognitive-communication deficits experienced by persons with aphasia (PWA). There is a growing body of research documenting attention and executive control impairments in PWA, but less work has been done to characterize the way in which these impairments relate to specific linguistic processes. To address this, the proposed project will experimentally investigate the relationship between executive attention (Kane and Engle, 2004) and specific linguistic and control processes during language-dependent tasks. We hypothesize that executive attention impairments exist in at least some PWA, and that the degree of this impairment should affect an individual's ability to process language. The project will conduct two experiments that will examine the effect of executive function and attention on PWA's ability to recognize words and process their meanings. The first experiment will characterize the ability of PWA to place emphasis on accuracy or speed during word recognition, and the second will examine the ability to set up ("upload") the processes needed to perform a lexical task. The project will also characterize executive function and attention in PWA and examine their relationship to control of linguistic performance. The two experiments will use the lexical decision task, in which participants indicate whether stimuli are real words or made-up words, and the characterization of executive function and attention will use a battery of specialized tasks designed to measure specific aspects of these abilities in linguistic and nonlinguistic domains. We will test 20 PWA and 20 age-matched controls. Results will be interpreted using a mathematical model of the lexical decision task that has been widely applied in studies of normal individuals (diffusion modeling: Ratcliff, 1978). We predict that PWA and control's performance will differ on specific diffusion model parameters that will be related to how they process language and respond to different task constraints. We also predict that PWA will demonstrate worse performance than controls in the executive and attention tasks, with a greater decrement in performance in linguistic compared to nonlinguistic measures, and that these differences will be predictive of PWA performance on the lexical decision tasks. The project is relevant to health because it will reveal relationships between executive and attention functions and linguistic processing in PWA, using a rigorous and well-validated modeling approach. This is expected to have important implications for treatment of these individuals. This project will be part of a training program that will involve coursework in computational modeling and statistics, as well as mentorship and direct training from experts in the areas of aphasia, lexical processing, executive control, and diffusion modeling. The training entailed by this project will help prepare the applicant to become an independent investigator capable of generating translational research between experimental psychology and aphasiology.
This project is relevant to public health because it is intended to improve our understanding of the cognitive and linguistic deficits that frequently occur in persons with aphasia (PWA) after stroke. The underlying relationship between attention, cognitive control, and language impairments remain unclear in this population, which hinders the development of more effective diagnostic and treatment approaches. The current project will address this need by studying PWA and age-matched controls using a mixture of experimental, correlational, and computational techniques to rigorously test specific hypotheses about these underlying relationships.