title: Changes in N400 topography following intensive speech language therapy for individuals with aphasia.
abstract: Our goal was to characterize the effects of intensive aphasia therapy on the N400, an electrophysiological index of lexical-semantic processing. Immediately before and after 4 weeks of intensive speech-language therapy, people with aphasia performed a task in which they had to determine whether spoken words were a 'match' or a 'mismatch' to pictures of objects. Pre-therapy, people with aphasia exhibited an N400 mismatch effect that started over right hemisphere electrodes. Post-therapy, gains were seen in clinical measures of language ability, and the onset of the N400 was left-lateralized. No changes in the scalp distribution of the N400 were observed in healthy controls tested twice over the same 4 week interval. Since the distribution of the N400 after aphasia therapy differed from that of healthy controls, we conclude that it reflects the engagement of compensatory neural mechanisms for language processing rather than a return to a "normal" pattern of brain activation.
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS B3H 4R2, Canada.
authors.forename: K Ryan
authors.initials: KR
authors.lastname: Wilson
authors.forename: Heather
authors.initials: H
authors.lastname: O'Rourke
authors.forename: Linda A
authors.initials: LA
authors.lastname: Wozniak
authors.forename: Ellina
authors.initials: E
authors.lastname: Kostopoulos
authors.forename: Yannick
authors.initials: Y
authors.lastname: Marchand
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Newman
mesh_terms: D001037:Aphasia / Q000503:physiopathology* / Q000534:rehabilitation*; D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D007808:Language Therapy; D012660:Semantics; D013070:Speech Therapy