BDNF and Alzheimer disease: In vitro and in vivo experimental studies have also clearly demonstrated a causal link between human AD neurodegeneration and impaired neurotrophin NGF/TrkA signaling pathway (Counts and Mufson, 2005; Schliebs and Arendt, 2006; Mufson et al., 2008; Cattaneo and Calissano, 2012), highlighting the cholinergic synapses as selectively affected in incipient AD progression (Davies and Maloney, 1976; Perry et al., 1978; Whitehouse et al., 1981; Coyle et al., 1983; Wong et al., 1999; Bell et al., 2006; Hampel et al., 2018).