BDNF and Alzheimer disease: Indeed, the gene and protein expression of BDNF is severely reduced in the hippocampus and temporal and frontal cortex regions in Alzheimer disease brain (Phillips et al., 1991; Hock et al., 2000; Patapoutian and Reichardt, 2001; Fahnestock et al., 2002; Michalski and Fahnestock, 2003).