At the same time it was shown that different functional groups of genes have opposite directions of age-related changes of their expression levels. Two independent studies on the relationships between gene expression in the brain and aging using global transcriptome profiling by microarray techniques (Colantuoni, et al., 2011; Kang, et al., 2011; Lu, Pan, Kao, Li, Kohane, Chan, et al., 2004; Somel, Franz, Yan, Lorenc, Guo, Giger, et al., 2009) provide evidence that genes involved in nervous system development, synaptic plasticity, vesicular transport and mitochondrial functions correlate negatively (reduce their expression) with age. In contrast, a set of genes that correlate with age positively is significantly enriched by genes involved in DNA repair and binding, the regulation of transcription, inflammatory processes, myelinization (i.e., the construction of the myelin sheath around a nerve fiber) and lipid metabolism. Altogether these findings suggest significant changes in the transcriptome of the aging brain, which are related to a number of crucial functions of the brain, such as brain plasticity, learning and memory among others.
