Fig. 5.

For PCA, LoCA, and Symmetric LoCA, the first two basis vectors in order of reconstruction error are shown from above (left) and below (right). Darker surface points are displaced to a greater degree by the basis vector. For each basis, the number of basis vectors required to account for 90 percent of the ventricular shape variation is given in parentheses. The first PCA vector captures a symmetric change to both occipital horns along with expansion of the left frontal horn, while the second represents a nearly uniform inflation of the entire surface. LoCA finds vectors which affect each side separately while symmetric LoCA affects both simultaneously: its first vector lengthens both occipital horns while its second expands both frontal horns.