Deformation Based Morphometry (DBM) is a relatively new method used for characterizing anatomical differences
among populations. DBM is based on the analysis of the deformation fields generated by non-rigid registration
algorithms, which warp the individual volumes to one standard coordinate system. Although several studies have
compared non-rigid registration algorithms for segmentation tasks, few studies have compared the effect of the
registration algorithm on population differences that may be uncovered through DBM. In this study, we compared DBM
results obtained with five well established non-rigid registration algorithms on the corpus callosum (CC) in thirteen
subjects with Williams Syndrome (WS) and thirteen Normal Control (NC) subjects. The five non-rigid registration
algorithms include: (1) The Adaptive Basis Algorithm (ABA); (2) Image Registration Toolkit (IRTK); (3) FSL
Nonlinear Image Registration Tool (FSL); (4) Automatic Registration Tools (ART); and (5) the normalization algorithm
available in SPM8. For each algorithm, the 3D deformation fields from all subjects to the atlas were obtained and used to
calculate the Jacobian determinant (JAC) at each voxel in the mid-sagittal slice of the CC. The mean JAC maps for each
group were compared quantitatively across different nonrigid registration algorithms. An ANOVA test performed on the
means of the JAC over the Genu and the Splenium ROIs shows the JAC differences between nonrigid registration
algorithms are statistically significant over the Genu for both groups and over the Splenium for the NC group. These
results suggest that it is important to consider the effect of registration when using DBM to compute morphological
differences in populations.
Mathematical difficulty affects approximately 5-9% of the population. Studies on individuals with dyscalculia, a
neurologically based math disorder, provide important insight into the neural correlates of mathematical ability. For
example, cognitive theories, neuropsychological studies, and functional neuroimaging studies in individuals with
dyscalculia suggest that the bilateral parietal lobes and intraparietal sulcus are central to mathematical performance. The
purpose of the present study was to investigate morphological differences in a group of third grade children with poor
math skills. We compare population averages of children with low math skill (MD) to gender and age matched controls
with average math ability. Anatomical data were gathered with high resolution MRI and four different population
averaging methods were used to study the effect of the normalization technique on the results. Statistical results based on
the deformation fields between the two groups show anatomical differences in the bilateral parietal lobes, right frontal
lobe, and left occipital/parietal lobe.
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