The high variability of the transcriptome among distinct brain regions has been confirmed in another study (Strand, et al., 2007) comparing the global transcriptome analyses in the motor cortex, caudate nucleus, and cerebellum, using the same Affymetrix microarray technique. In this study approximately 30 genes were detected that showed region-specific expression of the “on/off” type. Comparing these three distinct substructures of the brain across 12 individuals (eight men and four women, whose ages ranged from 36 to 77), the researchers showed that human individual variability in gene expression neither obscures nor significantly contributes to regional differences (Strand, et al., 2007). In contrast, there were many fewer differences found between cortical areas within the individual brain (i.e., between areas within the same individuals) than in regional differences between individuals (i.e., within one area between different individuals), despite their substantial differences in function and the cellular architecture of the neurons in the cerebral cortex of the brain (Khaitovich, Muetzel, She, Lachmann, Hellmann, & Dietzsch, 2004; Naumova, et al., unpublished data). For example, only one of the 4,998 genes with detectable expression differences
