The data acquired by Davatzikos and colleagues (1996) was subsequently reanalyzed by Bookstein (1997) using shape-theoretic methods. In the Procrustes methods, developed for the statistical analysis of biological shape (Bookstein, 1989, 1997), a series of points are spread out along the callosal boundary and used to derive a warping field that matches one boundary with another. Affine components of neuroanatomical difference are first factored out by rotating and scaling configurations of point landmarks in each subject into least-squares correspondence with a Procrustes mean shape. Residual deformations that reflect individual anatomical differences are then expressed in terms of an orthogonal system of principal deformations derived from the bending energy matrix of the differential operator which governs the deformation (Bookstein, 1997). The deformations
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