APOE and Cognitive impairment: Synaptic dysfunction and loss correlate strongly with cognitive impairment in AD, and ApoE4, the major genetic risk factor for AD, has been shown to be involved in synaptic function and neuronal network activity (Dumanis et al., 2009; Filippini et al., 2009; Chen et al., 2010; Kim et al., 2014; Nuriel et al., 2017).