APOE and Parkinson disease: These results support the role of APOE4 (Serrano-Pozo et al., 2011) as a risk factor for Parkinson’s disease (Pankratz et al., 2006), where alpha synuclein may also be preferentially deposited in the CA2–CA3 regions of the hippocampus, insula, amygdala and cingulate cortex (Harding and Halliday, 2001; Bertrand et al., 2004).