HDAC9 and Alzheimer disease: Increasing histone H3 and H4 acetylation by means of HDAC inhibitors in the dorsal hippocampus enhances several types of hippocampal-dependent memories (Stefanko et al., 2009; Haettig et al., 2011), and also rescued hippocampal memory deficits in mouse models of AD (Ricobaraza et al., 2009; Kilgore et al., 2010) and on aged rats (Neidl et al., 2016).