BDNF and Cognitive impairment: In recent years, BDNF Val66Met polymorphism has been reported to interact with APOE ɛ4 on working memory, verbal and visual episodic memory, and the progression of mild cognitive impairment (MCI) (Forlenza et al., 2010; Ward et al., 2014; Lim et al., 2015; Gomar et al., 2016).