234 Chapter 8 Group comparison In controls the activation clusters in general were smaller compared to people with narcolepsy type 1 and no significant activation was seen in the brainstem. Formal comparison between groups elicited significantly greater activation in people with narcolepsy type 1 in the left calcarine and lingual gyri (Brodmann area 17; cluster size: 43 voxels; peak z-value: 3.88; cluster-corrected p-value = 0.0463; Z-max MNI coordinates: −42, −4, 36) when actively resisting sleep (Figure 2). No clusters were found with significantly more activation in controls compared to patients. Neither of the post hoc analyses with ESS scores and EDS duration as covariates of interest revealed significant correlations between these clinical markers and the observed group difference in the left calcarine and lingual gyri. Figure 2. Active sleep resistance group differences. Axial slices displaying significant activation clusters that were significantly more activated in people with narcolepsy type 1 than in controls during active sleep resistance. Analyses were cluster-corrected (p < 0.05), masked for grey matter, and a minimum cluster size > 20 voxels was used. Discussion The active sleep resistance paradigm is a feasible MRI task that elicits strong BOLD activation during the active sleep resistance condition in brain regions related to consciousness regulation, attention maintenance and sensory information processing. Within the active sleep resistance blocks patients showed significantly more activation in the left lingual and calcarine gyri compared to healthy controls. No significant correlation was found with ESS scores and EDS duration for patients in these regions, suggesting that the observed group differences are likely related to having narcolepsy and not the disease severity or duration. No studies have yet investigated the neural activation pattern of active sleep resistance using MRI. The widespread visual activation that is induced during sleep resistance likely results from a combination of active sleep resistance
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