title: Speech entrainment compensates for Broca's area damage.
abstract: Speech entrainment (SE), the online mimicking of an audiovisual speech model, has been shown to increase speech fluency in patients with Broca's aphasia. However, not all individuals with aphasia benefit from SE. The purpose of this study was to identify patterns of cortical damage that predict a positive response SE's fluency-inducing effects. Forty-four chronic patients with left hemisphere stroke (15 female) were included in this study. Participants completed two tasks: 1) spontaneous speech production, and 2) audiovisual SE. Number of different words per minute was calculated as a speech output measure for each task, with the difference between SE and spontaneous speech conditions yielding a measure of fluency improvement. Voxel-wise lesion-symptom mapping (VLSM) was used to relate the number of different words per minute for spontaneous speech, SE, and SE-related improvement to patterns of brain damage in order to predict lesion locations associated with the fluency-inducing response to SE. Individuals with Broca's aphasia demonstrated a significant increase in different words per minute during SE versus spontaneous speech. A similar pattern of improvement was not seen in patients with other types of aphasia. VLSM analysis revealed damage to the inferior frontal gyrus predicted this response. Results suggest that SE exerts its fluency-inducing effects by providing a surrogate target for speech production via internal monitoring processes. Clinically, these results add further support for the use of SE to improve speech production and may help select patients for SE treatment.
authors.affiliation: The Aphasia Lab, Department of Communication Sciences & Disorders, University of South Carolina, USA. Electronic address: jfridrik@sc.edu.
authors.forename: Julius
authors.initials: J
authors.lastname: Fridriksson
authors.affiliation: The Aphasia Lab, Department of Communication Sciences & Disorders, University of South Carolina, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Basilakos
authors.affiliation: Department of Cognitive Sciences, University of California Irvine, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Hickok
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, USA.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Bonilha
authors.affiliation: Department of Psychology, University of South Carolina, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Rorden
mesh_terms: D000368:Aged; D001039:Aphasia, Broca / Q000209:etiology / Q000473:pathology / Q000628:therapy*; D065711:Broca Area / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D013060:Speech / Q000502:physiology*; D013070:Speech Therapy / Q000379:methods*; D020521:Stroke / Q000150:complications* / Q000473:pathology; D016896:Treatment Outcome
keywords: Broca's aphasia; Non-fluent speech; Speech production; Treatment; Voxel-based lesion-symptom mapping