Fig. 1.

Anatomical representations of the first two principal components from the PCA. Voxelwise values denote how strongly the corresponding component is expressed in a given voxel. The voxelwise weights are in the range of −0.003–0.003, which is evident from the color scale; however, their absolute magnitude is less important rather than their relative magnitude compared with other voxels. Singular value decomposition was used to compute principal components; therefore, the magnitude of voxelwise values cannot exceed one, and squared voxelwise values have to add up to one. Component 1 is represented in Left, Component 2 is represented in Center (Component 2a), and Component 2 modulated by a lesion component derived from lesion maps is represented in Right (Component 2b).