exciteBCI: A Neuromodulatory Intervention for People with Stroke. Optimising for Translation into Clinical Practice

Alder, Gemma
Taylor, Denise
Signal, Nada
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Doctor of Philosophy
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Auckland University of Technology

Stroke is the leading cause of long-term adult disability. People with stroke describe locomotor disability as a significant ongoing concern. Despite being the primary focus of physical rehabilitation, the overall amount of locomotor rehabilitation received is low. As a result, there is an urgent need for innovative approaches to locomotor rehabilitation. Endogenous paired associative stimulation (ePAS) is a neuromodulatory intervention that pairs electroencephalography (EEG) derived signals known as the movement-related cortical potential (MRCP) with electrical stimulation. In people with stroke, ePAS has been demonstrated to enhance neural plasticity and improve locomotion. However, people with stroke describe ePAS as time-consuming and unchallenging, and the optimal intervention parameters have yet to be determined. This thesis aimed to optimise the intervention delivery of exciteBCI, a portable medical wearable device in the prototype stage designed to deliver ePAS during locomotor rehabilitation. A pragmatist philosophical approach framed the research, and mixed methods were used to support intervention delivery optimisation from both a neurophysiological and clinical use perspective.

The first research objective was to optimise the stimulation parameters of the ePAS intervention. This objective was addressed using a systematic review (manuscript I) and a factorial study with repeated measures (manuscript II). The systematic review critically appraised the evidence for the efficacy of lower limb paired associative stimulation (PAS) and the optimal stimulation parameters. Findings revealed moderate-to-poor quality evidence to support that a single session of lower limb PAS can modulate corticomotor excitability in healthy people and people with stroke. Across experiments, intervention stimulation parameters were highly variable, limiting conclusions about optimal parameters. Subsequently, a factorial study (manuscript II) investigated ePAS intervention efficacy in healthy people when stimulation intensity and movement parameters were manipulated. ePAS interventions were significantly more effective at increasing corticomotor excitability compared to control interventions, except in the case of the low intensity-voluntary ePAS intervention. Findings also confirmed that stimulation intensity and movement type treatment parameters interact within ePAS interventions. However, substantial inter-individual variability in intervention responses were observed. This highlighted the possibility that inaccuracies in the manual feature extraction of MRCP signals obfuscate the timing of the pairings. In response, a reliability study (manuscript III) was undertaken to determine the intra- and inter-rater reliability of EEG experts’ identification of the peak negativity feature from averaged MRCPs obtained from healthy people and people with stroke. Findings demonstrated excellent intra- and inter-rater reliability for the voluntary movement condition and low to moderate intra- and inter-rater reliability for the imagined movement condition. Together, the findings from the neurophysiological studies strengthened the case for prioritising voluntary-based movements as part of the exciteBCI intervention design.

The second objective of this research was to optimise the usability and acceptability of the exciteBCI to support its clinical translation. Guided by the International Organization for Standardization (ISO) 9241-210:2019 standard, an iterative user-centred design approach supported by a qualitative descriptive methodology was undertaken (manuscript IV). People with stroke and physiotherapists participated in single session sprint cycles and sustained user testing where exciteBCI augmented locomotor rehabilitation. Findings revealed that users perceived exciteBCI to be an acceptable rehabilitation technology which could fit within a rehabilitation context and provided clear device requirements to guide future device development. More broadly, the study highlighted important understandings that inform the design and development of rehabilitation technologies.

This thesis demonstrates a rigorous approach to optimising the delivery and development of a complex rehabilitative technology. The research has made a significant contribution to the development of exciteBCI in preparation for evaluation of efficacy and implementation in clinical practice. This research illustrates the value of drawing on both neurophysiological and clinical knowledge in the development of new technologies and offers a framework for the development of complex rehabilitative technologies.

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