Movies on the Mind: Using Naturalistic Stimuli to Assess Perception, Cognition, and Awareness in Patients with Disorders of Consciousness
Abstract
Standardized behavioural assessments of awareness remain the gold standard for patients with disorders of consciousness (DOC) and inform diagnosis, prognosis, and medical decision-making. However, recent neuroimaging research has identified a small but significant number of DOC patients who retain perceptual and cognitive abilities not evidenced by their behaviour. Therefore, it is imperative to develop assessment techniques to identify and characterize the conscious experiences of patients with DOC. This thesis presents a novel movie-based electroencephalographic (EEG) assessment of perceptual and cognitive function in DOC patients. In Chapter 2, we calculated EEG inter-subject correlations (ISCs) in healthy controls and DOC patients to index higher-order “executive” processing of two types of movie stimuli (audio-visual, audio-only). Contrary to their behavioural diagnosis, 25% and 30% of patients showed preserved perceptual and cognitive abilities necessary to process the audio-visual and auditory movies, respectively. In Chapter 3, we determined whether a translated version of the auditory movie could be used to assess French-speaking populations of DOC patients. Here, two groups of healthy controls (English and French-speaking) showed comparable degrees of ISCs that occurred at roughly the same timepoints across languages. In Chapter 4, we explored the prognostic utility of ISCs, functional connectivity, and source localized EEG activity in a cohort of patients with severe acute brain injury. ISCs and functional connectivity, but not source localized activity, were marginally predictive of outcomes after severe brain injury. Over three studies, we developed and validated a novel EEG assessment of perceptual and cognitive function in DOC patients, demonstrated its potential application in English and French populations, and established the feasibility of this assessment in acutely brain-injured patients.