Subsequent studies revealed that sodium butyrate injection in a transgenic mouse model of AD is correlated with decreased tau phosphorylation and restoration of dendritic spine density in hippocampal neurons (Ricobaraza et al., 2010), and prolonged treatment in a transgenic mouse model for amyloid deposition (APP/PS1 mice) improved associative memory by increasing both hippocampal histone acetylation and the expression of genes implicated in associative learning (Govindarajan et al., 2011). The gene discussed is PSEN1; the disease is Alzheimer disease.