GRIN2B and Cognitive impairment: We found that elevation of pp32 decreased the acetylated levels of histone H3 at lysine 9 and 14, and histone H4 at lysine 5 and 12, and the mRNA and protein levels of synaptic genes GluR1, GluR2, NR2A, NR2B, Syp, and Syt1 with decreases of dendritic spine density in the hippocampus of the cognitive-impaired aged mice, resulting in cognitive deficits.