Finding the right words: Transcranial magnetic stimulation improves discourse productivity in non-fluent aphasia after stroke

Abstract

Background: Loss of fluency is a significant source of functional impairment in many individuals with aphasia. Repetitive transcranial magnetic stimulation (rTMS) administered to the right inferior frontal gyrus (IFG) has been shown to facilitate naming in persons with chronic left hemisphere stroke and non-fluent aphasia. However, changes in fluency in aphasic participants receiving rTMS have not been adequately explored. Aims: To determine whether rTMS improves fluency in individuals with chronic nonfluent aphasia, and to identify aspects of fluency that are modulated in persons who respond to rTMS. Methods & Procedures: Ten individuals with left hemisphere MCA strokes and mild to moderate non-fluent aphasia participated in the study. Before treatment participants were asked to describe the Cookie Theft picture in three separate sessions. During treatment all participants received 1200 pulses of 1 Hz rTMS daily in 10 sessions over 2 weeks at a site that had previously been shown to improve naming. Participants repeated the Cookie Theft description 2 months after treatment. Five participants initially received sham stimulation instead of real TMS; 2 months after sham treatment these individuals received real rTMS. Performance both at baseline and after stimulation was coded using Quantitative Production Analysis (Saffran, Berndt, & Schwartz, 1989) and Correct Information Unit (Nicholas & Brookshire, 1993) analysis. Outcomes & Results: Across all participants (n = 10), real rTMS treatment resulted in a significant increase in multiple measures of discourse productivity compared to baseline performance. There was no significant increase in measures of sentence productivity or grammatical accuracy. There was no significant increase from baseline in the sham condition (n = 5) on any study measures. Conclusions: Stimulation of the right IFG in patients with chronic non-fluent aphasia facilitates discourse production. We posit that this effect may be attributable to improved lexical-semantic access.