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Pairing Reading Treatment with Transcranial Direct Current Stimulation for Adults with Aphasia
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- Author / Creator
- Lee, Grace S
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Background. Damage to language areas of the brain often leads to a language disorder called aphasia, which impairs speech, writing, and understanding. Sixty-eight per cent of people with aphasia (PWA) also present with alexia, a reading impairment. There is an urgent need for efficacious therapies to remediate reading disorders as the ability to read independently is essential for life participation. Many existing reading treatments target single word reading and demonstrate little generalization to larger bodies of text. In contrast, multimodal reading therapies targeting different reading skills have resulted in functional treatment gains.
Recently, Transcranial Direct Current Stimulation (tDCS) has been explored as a potential adjunct to augment outcomes of traditional language treatment. tDCS modulates ongoing neural activity to prime the brain for long-term consolidation. Extensive research demonstrates the positive effects of tDCS on the spoken language treatments. However, there remains insufficient investigation on the effects of pairing tDCS with reading treatments.
This study explored the effects of tDCS paired with two multimodal intensive reading treatments with four individuals with alexia. In addition to behavioural outcome measures, eyetracking was also used as a real-time measure of cognitive mechanisms during reading, to provide further insight into treatment induced changes.
Methods. Two treatments were delivered within the present study. In Treatment 1, a reading fluency and phonological treatment (RF+PT) was delivered to two participants (P1 and P2) with chronic mild-moderate alexia, and impaired sublexical skills. In Treatment 2, a reading fluency and reading comprehension treatment (RF+RC) was delivered to another two individuals (P3 and P4) with chronic mild alexia and intact sublexical skills. In a double-blinded, crossover design, all participants received 40 hours of reading treatment (2 hrs/day x 5 days/week x2 weeks = 20 hours for each phase with 4 week washout between phases = 40 hrs of treatment total), in conjunction with active anodal-tDCS (a-tDCS) and sham-tDCS (s-tDCS).
Individual’s sublexical skills, reading fluency and reading comprehension were assessed before and after each treatment phase to determine if there were treatment gains. As well, eye-movement measures of dwell time, fixation count and regressions were taken during silent reading. Participants read passages with congruent or incongruent antecedents and anaphors. Treatment induced changes were determined by repeated measures ANOVA, treatment effect sizes (Cohen’s d), and McNemar’s Chi Square.
Results. Participants who received RF+PT treatment (P1 & P2) made gains in sublexical skills. Treatment with RF+PT and a-tDCS coincided with greater gains in reading comprehension in P1; P2 demonstrated limited behavioral and eye movement changes after treatment, regardless of tDCS condition. Following RF+RC treatment, greater gains in reading comprehension occurred in the first phase of treatment for both P3 and P4. A-tDCS with either treatment type did not appear to result in significant increases in sublexical skills or reading fluency of connected text. Across participants, there was generally a decrease in single word reading speed after treatment with a-tDCS relative to treatment alone.
In 3 participants, a-tDCS led to more changes in their eye movements when reading inconsistent passages, specifically in their dwell time and fixation counts. These larger shifts in dwell time and/or fixation count when reading inconsistent passages, tended to coincide with gains in reading comprehension. However, gains in reading comprehension were not observed when there were changes in regressions as well.
Conclusion. The improvements in reading skills demonstrate that an RF+PT approach is effective for individuals with mild-moderate alexia and improving sublexical skills. The lack of behavioural and eye movement gains in P2 suggests that impaired and/or non-improving sublexical skills may hinder subsequent gains in reading fluency and comprehension. The pattern of results in P1 and P2 also provides evidence that a-tDCS promotes further gains in areas that were already improving.
Gains in reading comprehension in the first phase of RF+RC show that individuals with mild alexia respond optimally to the first 20 hours of treatment, regardless of tDCS condition. In these individuals, there may be limited treatment gains with ongoing treatment and/or with a-tDCS.
Preliminary eye-movement changes and corresponding reading comprehension gains suggest the mechanism underlying gains in reading comprehension may be treatment-induced modifications in dwell time and fixation count with minimal changes in regressions when encountering comprehension breakdowns. There are benefits for the use of tDCS with multimodal reading therapies. -
- Graduation date
- Spring 2020
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.