Individuals with aphasia can differ widely in their symptom severity and the degree to which they experience long-term alterations to varying levels of language processing (e.g., acoustic, phonological, semantic). An important factor in recovery is the interventions received post symptom onset. To develop a well-tailored therapy plan, however, a person with aphasia must have their language impairments precisely diagnosed. Clinically characterizing a patient’s language impairment is crucial but can be challenging. Traditional behavioral tests are prominently used in diagnosis, but capture only overt performance. Neural measures, such as event-related potentials (ERPs) and temporal response functions (TRFs), are sensitive to implicit processes of language (e.g., phonological, lexical, semantic) and have great potential to improve current foundational understanding of aphasia as well as our knowledge about specific clinical cases (Silkes & Anjum, 2021). By investigating such neural measures, we may be able to detect residual “implicit” language skills that have utility guiding recovery and therapy planning. In our study, we combine two EEG‑based approaches, ERPs and TRFs, to probe multiple levels of speech processing in individuals with aphasia.
Traditionally, ERPs necessitate repeated presentation of isolated stimuli (e.g., spoken words) in order to average the neural response to those stimuli and detect small time-locked signals. TRFs, alternatively, use simple machine learning techniques to create functions that can predict features of a sound stimulus (e.g., amplitude envelope, word frequency) based on the EEG response (or vice versa to predict the EEG response to a sound stimulus feature). This TRF approach facilitates the use of naturalistic language stimuli, without the need for repeated similar trials like ERPs. We are currently testing a paradigm, wherein participants listen to short spoken recordings, to elicit both ERPs and TRFs simultaneously. Our goal is to evaluate each and assess their utility as neural markers of language ability and aphasia symptomatology. This study aims to advance understanding of the neural mechanisms of language processing in aphasia using TRFs and ERPs in various listening paradigms.