19 Introduction Functional neuroimaging in narcolepsy type 1 Functional MRI (fMRI) is most commonly conducted during so-called resting state (to extract information about intrinsic brain networks) or during specifically designed tasks (to extract information related to specific cognitive processes). Both types of fMRI paradigms have been applied to mainly narcolepsy type 1. Using resting state fMRI, multiple studies have reported decreased resting state activity within the default mode network as the main resting network [111114], which also seemed less connected to networks that are normally active during cognitive tasks (salience, dorsal attention and executive network) [115]. The combination of deactivation of the default mode network and upregulation of the cognitive networks is essential to perform well in cognitive tasks. The decreased coupling of these networks in narcolepsy suggests a dysregulation of mental resources in favour of staying awake over actual task performance [116]. Limbic network activity has been thoroughly assessed using fMRI taskbased studies on emotional processing and cataplexy attacks [117-119]. These studies have reported both higher and lower hypothalamus activity in combination with mainly enhanced amygdala and reward system activity during emotional processing and cataplexy attacks. Loss of hypothalamic control over the mesolimbic reward system in NT1 during emotional stimuli seems responsible for triggering cataplexy attacks. Limited fMRI studies have been performed to investigate the neural activation patterns underlying other common symptoms of narcolepsy type 1, and none had yet focussed on vigilance impairments and the occurrence of unwanted sleep attacks. In Chapters 7 and 8 we present results from task-based fMRI studies investigating brain activation patterns during the sustained attention to response task (SART) and an active sleep resistance paradigm in individuals with narcolepsy type 1 compared to healthy controls. 1
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