Hierarchical clustering of significantly regulated genes. Probe sets represent 18 brain samples from mice at 3, 5, and 8 months of age. For clarity, only representative portions are shown (55 of 255 probe sets corresponding to 227 genes and all downregulated probe sets (12 probe sets corresponding to 8 genes). Upregulated genes are shown in red and downregulated genes in green. This figure shows the upper quartile of the image. For the full image depicted in Fig. 4 please see Additional File 2. Additional File 10 contains full clustering information for all 227 genes.