The authors would like to thank David Kennedy of the Centre for Morphometric Analysis at MGH for segmented brain data. The work was supported by the EPSRC/MRC-funded Medical Image and Signal IRC (GR/N14248/01), Integrated Brain Image Modelling (EPSRC GR/S82503/01) and Modelling, Understanding and Predicting Structural Brain Change (EPSRC GR/S48844/01).