Correlated gene clusters. (A) Representation of the voxelation process on a normal hemisection. (B) Gene expression correlation matrices for the normal and Alzheimer's hemisections. The correlation of expression levels across voxels between any two genes is read by looking along the relevant row and column, and finding the intersection. (C) Gene expression correlation matrices for the subset of genes common to both specimens that display a spatial expression correlation coefficient of >0.92 with at least one other gene within the same brain. (D) Spatial gene expression patterns for the subset of correlated genes. The voxels are laid out in linear fashion forming the columns of the matrices, whereas the genes form the rows. The relative level of expression of a gene in any particular voxel can be deduced by reference to the scales below. The two clusters of genes are apparent, and although each cluster consists of highly correlated expression patterns within both the normal and Alzheimer's hemisections, the patterns of gene expression are different between the two hemisections.