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Fig 1. Mean coefficients associated with the first 9 eigenvectors for all groups. The displacement of each graphic point on the hippocampal surface from template (or atlas, which was a manually outlined hippocampus of a healthy subject not otherwise included in this study) to target (or subject) is represented by a vector. Crosshairs represent the standard deviation of each vector. The figure shows the first 9 eigenvectors, which explained 75% of the total variance and were used to compute asymmetry measures for each group. Of the first 3 eigenvectors, eigenvectors 1 and 3 showed large differences between the control group and each of the MTS groups but showed very similar values for the MTS groups. Eigenvector 2 showed large differences between the control and MTS groups, as well as between the MTS groups. Because eigenvectors 1 and 3 show only minimal differences between the MTS groups, they minimally contributed to discriminating shape differences between the MTS groups. Eigenvector 2, for the MTS groups, showed similar absolute magnitudes. However, the left MTS groups showed a positive value, whereas the right MTS group showed a negative value. This indicates that the shape changes represented by eigenvector 2, comparing the right and left MTS hippocampi, were highly symmetrical.
