227 Active Sleep Resistance in Narcolepsy Type 1 Introduction The maintenance of wakefulness test (MWT) is a polysomnographic procedure to quantify daytime sleepiness and is often used to assess fitness to drive in people with excessive daytime sleepiness. During four daytime 40-min sessions at two-hour intervals, subjects are asked to resist the urge to fall asleep while sitting down in a soporific environment [308]. The underlying neural correlates of active sleep resistance largely remain to be discovered and could provide important insights in sleep-wake regulation in health and disease. The MWT is frequently used as objective parameter in pharmacological trials and in the assessment of fitness to drive in people with narcolepsy type 1 [309]; a sleep disorder characterized by excessive daytime sleepiness and cataplexy (transient episodes of muscle weakness). People with narcolepsy type 1 often have difficulty resisting sleep during repetitive tasks within a work or academic environment, or while participating in traffic [4]. To date, little is known about the neural activation of patients’ sleep attacks and their continuous fight to remain wakeful. In this study, we quantified brain activation patterns related to sleep resistance in healthy, and troubled sleepers with narcolepsy type 1, through concurrent functional magnetic resonance imaging and electroencephalography (fMRI-EEG) recordings. Use of simultaneous fMRI-EEG measurements is crucial for reliable sleepwake fMRI research, as it allows for objective consciousness assessment and task adherence, while simultaneously recording whole brain activation patterns. Combining these two powerful neuroimaging techniques brings its challenges, as the EEG signal is subject to ballisto-cardiac (BCG), and MRinduced gradient and helium pump artefacts [310]. We have recently developed a unique carbon-wire loop-based (CWL) artefact correction approach that carefully filters these artefacts, while preserving true brain signals for sleepwake scoring [311]. The aim of this study was to validate feasibility of the active sleep resistance paradigm through simultaneous fMRI-EEG recordings, and to assess brain activation patterns related to sleep resistance in health and disease. We hypothesize people with narcolepsy type 1 to find it more difficult to remain wakeful as compared to controls, and patients to more heavily depend on activation of the ascending reticular activating system and attention regions when actively resisting sleep. 8
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