UC San Diego

Post-stroke aphasia is a language disorder that can significantly impact quality of life. The hallmark symptom of aphasia is difficulty accessing words (i.e., lexical access), a process critical for both language production and comprehension. Since aphasia was first identified in the 1800s, researchers have investigated the mechanisms underlying these deficits to understand how to treat them. Although lexical access deficits have traditionally been conceptualized as primarily linguistic in origin, contemporary research suggests that certain cognitive processes that support fluent language use (e.g., attention and cognitive control) also play a substantial role in these impairments. Much of the evidence for attentional and cognitive control impairments in aphasia comes from explicit behavioral tasks that rely on overt responses (e.g., reaction time, accuracy); however, some people with aphasia have latent, intact language knowledge that is not always accessible through such explicit measures, highlighting the need for approaches that capture underlying implicit processes. This dissertation investigates the role of attentional processes in lexical access and its breakdown in aphasia, across tasks spanning a continuum of implicit to explicit processing, in both people with aphasia and age-matched controls. Study 1 examines how lexical-semantic cues influence cognitive effort during complex sentence processing using pupillometry. Study 2 investigates rapid attentional shifting ability, as indexed by performance on the attentional blink paradigm, and its association with word retrieval deficits. Study 3 explores how bottom-up, exogenous attentional orienting cues modulate lexical processing during spoken word recognition, using an eye-tracking-while-listening task. Across studies, converging findings indicate that people with aphasia show impairments in attentional processes across a range of processing levels, from relatively implicit to more explicit, potentially reflecting difficulty with allocating attentional resources to meet the task demands. Such disruptions in attention allocation may, in turn, contribute to impaired lexical access in aphasia. Together, these results advance our understanding of the cognitive mechanisms underlying language impairments in aphasia.