235 Active Sleep Resistance in Narcolepsy Type 1 and open vs. closed eyes. Research by Qin et al. (2012) with similar power and block-design setup suggests that our task activation clusters are roughly double the size of what could be expected from just using open vs. closed eyes conditions [314]. This implies that our measured effect, to a considerable extent, is attributable to active sleep resistance. Previous EEG research in psychiatric disorders [315] and during the MWT in multiple sleep disorders (including narcolepsy type 1) revealed that slowing of occipital activity is related to microsleep occurrence [269]. The increased occipital activation during the task likely reflects the opposite process, where participants actively recruit their occipital mental capacities to remain wakeful. The increased activation in people with narcolepsy type 1 in the visual cortex could be explained by an enhanced need of visual focus to resist sleep, or lower activation of this area during waking rest in patients, reflecting a more rapid descent in the alertness level of individuals with narcolepsy type 1. Patients generally reported that they had to intensely focus on all available stimuli during the sleep resistance condition. Similar patterns were seen within the same sample when performing the sustained attention to response task (SART). In this study, patients already had to utilize more cognitive effort to maintain vigilant at the start of the task, compared to healthy controls that benefited more from their cognitive reserves as the task progressed [266]. The between-group differences in the present study are, however, subtler than we hypothesized. A possible explanation could be that patients already had to utilize some of their ability to resist sleep in the waking rest condition, albeit to a lesser extent than in the sleep resistance condition. Larger participant groups and/or longer task blocks would allow to better grasp the neural substrate of active sleep resistance in both healthy and troubled sleepers. Eye opening and fading of alpha activity generally started a few seconds after instructions of active sleep resistance were presented. More widely known as the Berger effect, this phenomenon of alpha frequency blockade when opening ones’ eyes [316] was used to review task adherence in the present study. The delay, however, differed per subject and was typically longer for patients (Appendix A). In combination with the presence of sleep bouts in patients this emphasizes the importance of including simultaneous EEG measurements when conducting fMRI measurements in central disorders of hypersomnolence. Objective monitoring of vigilance has been sporadically included in other studies, but is necessary in this sleepy population to verify task adherence and continuous wake during task-based and resting-state fMRI [76]. Active sleep resistance induced activation within consciousness, attention regulation and visual cognitive processing-related regions. The increased 8
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