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Targeted use of transcranial direct current stimulation for cognitive modulation after traumatic brain injury: A neurophysiological and behavioural investigation

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Title: Targeted use of transcranial direct current stimulation for cognitive modulation after traumatic brain injury: A neurophysiological and behavioural investigation
Authors: Li, Lucia Mengxi
Item Type: Thesis or dissertation
Abstract: Cognitive control requires the coordinated function of large-scale brain networks. The interactions between the Salience Network (SN) and Default Mode Network (DMN) are thought to be particularly important. Traumatic Brain Injury (TBI) commonly leads to cognitive dysfunction, and is also associated with abnormal SN and DMN function and connectivity. Transcranial direct current stimulation (TDCS) has been extensively studied as a tool for cognitive enhancement. However, there is high variability in the reported behavioural benefits of TDCS, and little understanding of how it affects the brain networks mediating cognitive control. The overarching aim of this thesis is to investigate the potential of TDCS for improving cognitive dysfunction after TBI. Chapter 3 investigates whether TDCS has the potential to modulate cognitive function in healthy controls, using bi-parietal TDCS in cognitive tasks with strong hemispheric lateralisation. In Chapters 4 and 5, I acquire functional MRI (fMRI) concurrently to applying TDCS to the SN, in order to assess the effects of TDCS on both brain networks and cognitive control (assessed using a response inhibition task, the Stop Signal Task). I also investigate whether structural connectivity of cognitive networks influences the response to TDCS. In Chapters 7-9, I apply this TDCS strategy to a cohort of chronic TBI patients. Chapter 7 assesses whether single-session SN TDCS improves response inhibition, whether white matter damage influences any response to stimulation and whether TDCS can improve abnormal network function. Chapter 8 presents a targeted analysis of the effects of multi-day anodal TDCS treatment on response inhibition and brain network function. Chapter 9 presents the effect of multi-day anodal TDCS treatment on a wider range of cognitive measures. In summary, this thesis investigates the proof-of-principle that TDCS can be used for cognitive rehabilitation after TBI. Through a progressive set of experiments in healthy and TBI participants, I assess the effects on cognitive function as well as on key cognitive control networks, and explore factors which may explain variability in responses to TDCS. The work presented within this thesis supports a multimodal approach to conducting TDCS studies in the cognitive field, with an emphasis on concurrent behavioural and neurobiological assessment, as well as highlighting the importance of directly addressing patient heterogeneity in TBI interventional studies.
Content Version: Open Access
Issue Date: Jul-2018
Date Awarded: Dec-2018
URI: http://hdl.handle.net/10044/1/90486
DOI: https://doi.org/10.25560/90486
Copyright Statement: Creative Commons Attribution NonCommercial Licence
Supervisor: Sharp, David
Sponsor/Funder: Wellcome Trust (London, England)
Funder's Grant Number: 103429/Z/13/Z
Department: Department of Medicine
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Medicine PhD theses

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