For example, a decreased methylation level of the NR2B gene corresponds to increased NR2B mRNA and protein expressions in mice following chronic ethanol treatment,12 and an increase in the methylation level of the NR2B gene corresponds to decreased NR2B mRNA and protein expressions in mice with kainic acid‐induced epilepsy or benzo(a)pyrene (BaP)‐induced cognitive impairment.13, 35. This evidence concerns the gene GRIN2B and Cognitive impairment.