The electrophysiology of aphasia: A scoping review

Objective: To systematically assess the body of literature using N400 and P600 as they relate to people with aphasia. The primary aim was to reveal patterns in the literature which could be used to direct future research in the development of clinically relevant Event-Related Potentials (ERPs) for language assessment, while also identifying gaps in existing knowledge and highlight areas of further inquiry. Methods: A literature search was performed on studies published before May 2021. Relevant studies on aphasia and the two ERPs of interest were assessed for quality, and the relationship between aphasia and these ERPs was explored. Results: A total of 721 articles were identified, with 30 meeting inclusion criteria. Although there is significant variation in the literature, this scoping review revealed people with aphasia show reduced amplitude, delayed latency and different distribution compared to controls, and that ERPs are modulated by severity of aphasia. Conclusions: To develop a relevant clinical tool for the management of aphasia, future research must strive to improve consistency within ERP methodology, with a greater number of diverse aphasia sub-types included in research. Significance: This scoping review reveals N400 and P600 represent promising potential biomarkers for the diagnosis and ongoing management of aphasia. (C) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V.