Fig. 1.

This figure shows significance maps computed after using (a) a single subject and (b) the average ICBM53 atlas brain as the registration target image, based on applying the Mann–Whitney U test, at each voxel, to the difference in the mean log Jacobian determinant between AIDS and control groups. Only voxels with P < 0.01 are displayed (red). Although using an average brain image as the target avoids the bias toward the particular geometry of a single subject, it led to (slightly) lower effect sizes. This is apparent in the subcortical gray matter where the intensity contrast with the surrounding white matter is lower in the average brain. However, the results using each template are very similar in their overall spatial extent and distribution. Template optimization for TBM, e.g., using “minimal deformation targets” (MDT) (Kochunov et al., 2002), and geodesic mean templates (Avants and Gee, 2004; Fletcher et al., 2004) is the subject of on-going study, by our group and others.