In hippocampus there is not always a significant change in AD (Ferrer et al., 1999; Holsinger et al., 2000; Garzon et al., 2002; Michalski et al., 2015), although some studies have reported that BDNF protein and mRNA decline (Phillips et al., 1991; Hock et al., 2000), and data from CA1 pyramidal neurons show a robust decline across the progression of dementia that correlates with cognitive decline and neuropathology (Ginsberg et al., 2006, 2010, 2019; Mufson et al., 2007; Nagahara et al., 2009). This evidence concerns the gene BDNF and Alzheimer disease.