Using a FreeSurfer registration, and intracortical MD measures of the PPMI data, two recent studies (224, 225) with cross-sectional and longitudinal (within 1-year follow up) analyses have found that compared to controls, PD patients had significantly increased MD in the frontal and occipital cortices; among PD patients these cortical MD changes correlated with worsened cognitive performance; furthermore, the posterior-cortical (i.e., medial temporal and temporo-occipital) MD significantly correlated with the increases of serum neurofilament light chain. Here, NEFL is linked to Parkinson disease.