High levels of gene expression are registered during brain maturation before the age of 20-25 (Somel, Franz, Yan, Lorenc, Guo, Giger, et al., 2009). As shown in two studies on transcriptome profiling in the brain from individuals of different ages, the gene expression rate reduces over time, reaching a plateau by the age of 30 years. After middle age (approximately 40 years) multiple changes in gene expression occur, which are clearly detectable at the age of 60-65 (Lu, Pan, Kao, Li, Kohane, Chan, et al., 2004; Somel, Franz, Yan, Lorenc, Guo, Giger, et al., 2009).
