215 Attention Regulation in Narcolepsy Type 1 presentation. This network is also implicated in attention initiation and errorrelated and visual information processing, all of which are fundamental SART domains [288-293]. The task-positive activation of the locus coeruleus is related to the increased state of arousal needed to complete the task [294]. The task-positive motor activation most likely reflects a combination of motor action through button presses and its preparation and inhibition (when a 3 was presented). Previous research has shown that performance in motorrelated vigilance tasks, such as the SART, depends on preparatory (motor) set [295-297]. In our study we observed significant task-positive activity in multiple motor regions that are considered to control the Bereitschaftspotential (readiness potential) as they continuously assess both the planning of potential motor responses and prevent false premature initiation by limiting activity in nonprimary motor cortical areas through the thalamus and basal ganglia [298, 299]. Notably, in this study, the left thalamus and subthalamic nucleus were also active while performing the task. Previous MRI-SART research only involving healthy participants found clear cingulo-opercular, frontoparietal and supplementary motor cortex activation, consistent with current understanding of attention systems in the brain [282, 283, 285]. These studies used a slightly different paradigm, including a baseline condition in which participants were instructed to keep responding to stimuli and a task condition similar to our moderate difficulty level [285]. Their main task effect is similar to ours, but generally smaller, as no significant clusters were reported in the cerebellum, thalamus, or basal ganglia. Discrepancies with our main task effect likely result from our different baseline condition in which no button presses were needed and our implementation of the higher difficulty level, which was substantially more difficult. Our results overlap with a substantial quantitative meta-analysis of 67 neuroimaging studies on different vigilance tasks, showing 11 neural clusters involved in vigilance regulation. In that analysis, significant activation was reported in the prefrontal cortex, anterior insula, parietal areas (intraparietal sulcus, temporo-parietal junction), and subcortical structures (cerebellar vermis, thalamus, putamen, midbrain). Similar to our study, a relative right lateralization of activation clusters was seen, which has been hypothesized as being related to maintaining stable attentional focus and response inhibition in studies using a similar Go/No-Go paradigm [297]. It seems contradictory that, despite the clear behavioural differences, the between-group and task-effect contrasts comparing both difficulty levels did not reach significance. This suggests that the neural differences are subtler than we hypothesized. Significant activation differences may be absent in the higher 7
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