Associations between locus coeruleus (LC) contrast and global cortical thickness. Associations with global cortical thickness are displayed separately for older adults (OA) and younger adults (YA) for (A) overall LC contrast (reflecting contrast of peak LC voxels across x-, y-, and z-dimensions), (B) contrast of the rostral LC, and (C) contrast of the caudal LC. Points indicate raw data. Model fit lines reflect the association between LC contrast and global cortical thickness after regressing out the effect of chronological age on thickness. 95% confidence intervals are shown in gray. Fit lines and confidence intervals were calculated using the mean value of chronological age within each age group. Differences in scales on the x-axes are due to overall LC being calculated as a latent variable in a structural equation modeling framework, whereas rostral and caudal LC contrast were calculated by averaging signal intensity contrast ratios.