Comment on “Hierarchical genetic organization of human cortical surface area” by Chen et al. [Science 335 (2012) 1634–1636 (supporting information)

Abstract

Grey matter pathology in MS is known to be extensive (Kutzelnigg et al., 2005) and clinically relevant, even in the early phase of the disease (Chard et al., 2002). Grey matter imaging studies in MS have contributed greatly to improving our understanding of the disease mechanisms (Hulst and Geurts, 2011). These studies generally refer to the Brodmann’s scheme for human cortex, which identifies separate cortical areas on the basis of the cellular structure and organisation. Functional MRI studies in MS commonly describe increased or decreased activation associated with specific tasks in specific cortical areas (Pantano et al., 2002); structural MRI studies in MS often report cortical atrophy and thinning of cortical regions (Calabrese et al., 2010). In addition to cortical volume and thickness, cortical region surface area can be estimated from brain imaging. However, little is known about changes in cortical surface area in MS. One study has reported a reduction in the cortical surface area of each hemisphere in MS patients when compared with controls (Hier and Wang, 2007); a more recent study has reported a smaller surface area of the precentral gyrus in MS patients than controls (Gorgoraptis et al., 2010). Although changes in the functional and structural organisation of the cortex have been the focus of imaging papers in MS for a long time, the factors that are responsible for variation in cortical volume and surface area in humans, independently of disease status, are only now becoming clearer. Genetic factors are emerging as important