Likewise, changes in neural plasticity in terms of altered long-term potentiation or long-term depression have been observed in relation to the BDNF Val66Met polymorphism in the human brain (Cheeran et al., 2008; Antal et al., 2010) as well as in animal models (Lu and Figurov, 1997; Woo et al., 2005). This evidence concerns the gene BDNF and major depressive disorder.