Moreover, with respect to the hyperactivity/hypoactivity of the glutamatergic system observed in AD (Butterfield and Pocernich, 2003), the increased NR2A subunit expression could reflect rather its hyperactivity since NR2A-containing receptors have a lower activation energy compared to those with NR2B (Erreger et al., 2005). This evidence concerns the gene GRIN2B and Alzheimer disease.