The increased vulnerability of VTA dopaminergic neurons in AD could be considered a symmetrical picture to the increased vulnerability of SNpc dopaminergic neurons in PD, or the degeneration of TH+ neurons in the LC in both AD and PD patients (German et al., 1992; Liu et al., 2008; Kelly et al., 2017; D'Amelio et al., 2018a). Here, TH is linked to Parkinson disease.