One point that must be addressed is how one can validate the accuracy of the thickness measures. This is of course a critical question as any neurobiological interpretation of results depends on the thickness measures accurately reflecting the width of the cortical gray matter. Towards that end, we have performed an extensive (and extremely dull!) series of validation studies. This includes direct comparison of the thickness measures we compute against histological thickness measures in the same tissue (Rosas et al., 2002), using published measures of average thickness such as von Economo (1929) in motor cortex, somatosensory cortex, gyral cortex, sulcal cortex and overall average cortical thickness (Fischl and Dale, 2000), comparison with manual measures from MRI in disease and control populations (Kuperberg et al., 2003), estimation of the stability of the thickness measures with respect to scanner platform, sequence type and analysis degrees of freedom (Han et al., 2006), voxel geometry and amount of acceleration (Wonderlick et al., 2009), as well as their robustness and sensitivity for detecting correlations with cognitive measures that are stable across scan session, scanner manufacturer
