APOE and Cognitive impairment: Scientists have reported cognitive impairment in ApoE knockout (ApoE-KO) mice (Liu et al., 2013), with cholinergic deficits (Gordon et al., 1995), decreased synaptic excitability (Veinbergs et al., 1999), amyloid-β (Aβ) deposition, and impaired function of synaptosomes (Keller et al., 2000).