The Effect of Transcranial Direct Current Stimulation on Discourse Production in Post-Stroke Chronic Aphasia

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Transcranial direct current stimulation (tDCS) may promote neuroplasticity and enhance language production in post-stroke chronic aphasia, however, its impact on higher-level language skills such as discourse production is uncertain. The aim of this PhD was to investigate the potential of tDCS as a rehabilitative tool alongside speech and language therapy (SLT) for improving discourse production in post-stroke chronic aphasia.

Study one and two systematically reviewed the evidence base of interventions for improving discourse production in post-stroke chronic aphasia. Across 45 relevant studies various treatments were identified, highlighting the promising growth in this area of aphasia research. Eighty-four percent of studies reported significant improvements in at least one discourse production measure. However, only a small number reported on psychometric properties and included functional communication and quality of life measures. It was concluded that further studies which include validated outcome measures are required to establish the effectiveness of different treatments and optimal treatment strategies.

The purpose of study three was to investigate in healthy older adults the effect of anodal tDCS on discourse production vs. sham stimulation and optimal electrode placement for targeting language production at discourse level. Results showed both left inferior frontal gyrus (IFG) and right IFG anodal tDCS conditions produced improvements in discourse production compared to sham stimulation, with the greatest number of within-group improvements resulting from left IFG stimulation.
The findings indicated that the left IFG may be an optimal stimulation site for the modulation of discourse in healthy speakers and supported further examination of tDCS as a rehabilitative tool for discourse impairments in persons with aphasia.

Study four was a double-blinded randomised feasibility study comparing SLT with and without tDCS in post-stroke chronic aphasia. Results supported the feasibility of tDCS as an adjunct to SLT. Preliminary efficacy data revealed improvements in both groups, but the addition of anodal stimulation over the left IFG resulted in greater improvements in discourse production and functional communication.
Date of Award1 Apr 2022
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMarousa Pavlou (Supervisor) & Isaac Sorinola (Supervisor)

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