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Auditory and Visual ERPs As Brain Vital Signs: The Evolving Halifax Consciousness Scanner

  • Author / Creator
    Carolyn Fleck-Prediger
  • Covert awareness is difficult to detect in patients with cognitive-motor dissociation after severe neurological injury. In order to avoid over-reliance on subjective measures which are error prone, neurological evaluations must include behaviour-based ratings and objective, technology-based measures. The Halifax Consciousness Scanner is an electroencephalography (EEG) based system that delivers stimuli and records a range of Event Related Potentials (ERPs) which can be used to infer sensory, perceptual, attention, memory and language capacities. This dissertation discusses disorders of consciousness (DoC), details issues pertaining to prognostication and differential diagnosis, and reviews present and emerging diagnostic options. The first paper reviews recent literature regarding the clinical utility of evoked and cortically derived ERPs for evaluating DoC. The second paper describes a pilot study conducted with the auditory HCS contrasting a patient’s ERP profile before and after intensive speech-language intervention. P300 responses remained stable, while the amplitude of the N400 improved with concurrent gains in language comprehension. The third paper details the clinical deployment of the auditory HCS for trial at various points of care across Canada. Twenty-eight survivors of severe brain injury were tested with the auditory version of the HCS. The latency of the HCS derived P300 responses correlated with scores on clinical scales. The fourth paper discusses the development of a visual ERP paradigm that may be used in conjunction with the HCS. In this study on healthy controls, the stimuli were delivered via the Raspberry Pi 3 personal computer and the data were collected with the MUSE portable headset. Robust P300 responses were detected in response to familiar, personally relevant stimuli. This dissertation adds to existing literature by summarizing the current methodologies for assessing DoC while highlighting the utility and limitations of long latency ERPs. It discusses point of care evaluations with the Halifax Consciousness Scanner and introduces the development of a language and literacy-free visual paradigm to complement the existing auditory stimuli.

  • Subjects / Keywords
  • Graduation date
    Fall 2019
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/r3-sgy5-3q25
  • 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.