199 Attention Regulation in Narcolepsy Type 1 for at least 24 hours prior to examination. All provided written informed consent prior to study start. The study was approved by the Medical Ethical Committee of Leiden University Medical Center (LUMC), The Netherlands (NL46982.058.14) and was conducted according to the Declaration of Helsinki. Sustained attention to response task During the regular SART, participants are shown single digits from 0 to 9 for 4.19 min and are asked to press a key when a digit appears (GO), unless the digit is a “3” (No-Go). As shown in Figure 1, a modified version of the SART was used in this study to identify the participants’ ability to adapt to changes in vigilance demand by introducing a baseline condition and two difficulty levels of moderate and higher difficulty. In the baseline block, participants were instructed to focus on the appearing digits-including 3s-without pressing the button, while in moderate and higher difficulty levels they were instructed to respond to non-3 stimuli by pressing a button using their right index finger. Each block consisted of 27 visual stimuli and in the moderate difficulty level the digits were visible for 250 ms compared to just 100 ms in the higher difficulty level, to create a state of higher vigilance demand. A fixation cross was presented after the digit to make sure the participant had enough time to respond, and each stimulus-cross combination lasted for 1150 ms in total. A short instruction screen was shown when transitioning between different conditions. Our test consisted of four consecutive repetitions of the baseline, moderate difficulty, and higher difficulty blocks, ending with an extra baseline block and altogether with instructions lasted 9 min. Participants were instructed to focus equally on accuracy and speed while performing the task. The task was explained and briefly practiced before entering the MRI scanner. 7
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