2.9. Brainstem analysis

For the statistical comparison (ANOVA) based on our initial hypotheses, that is, regarding the activation differences in the LC between patients and controls, we used the small volume correction (SVC) method to account for the small size of the brainstem/midbrain nuclei. The LC was a priori anatomically defined as region of interests (ROIs). To obtain the anatomically most precise ROIs, we used the LC mask image in the MNI coordinate space based on Keren et al., (2009), which represents the extent of peak LC signal distribution, obtained from a sample of 44 healthy adults using high‐resolution T1‐weighted Turbo Spin Echo MRI. The statistical significance was set to p <.05, FWE voxel‐level corrected.