[en] Cortical surface area is an increasingly popular brain morphology metric that is ontogenetically and phylogenetically distinct from cortical thickness and offers a separate index of neurodevelopment and disease. However, the various existing methods for assessment of cortical surface area from magnetic resonance images have never been systematically compared. We show that the surface area method implemented in FreeSurfer corresponds closely to the exact, but computationally more demanding, mass-conservative (pycnophylactic) method, provided images are smoothed. Thus, the data produced by this method can be interpreted as estimates of cortical surface area, as opposed to areal expansion. In addition, focusing on the joint analysis of thickness and area, we compare an improved, analytic method for measuring cortical volume to a permutation based non-parametric combination (NPC) method. We analyze area, thickness and volume in young adults born preterm with very low birth weight, using both methods and show that NPC analysis is a more sensitive option for studying joint effects on area and thickness, giving equal weight to variation in both of these two morphological features.
