Although apathy is highly prevalent in PD from its early stages, the exact pathogenesis of apathy in PD are partially understood at present (46), being likely a combination of progressive alteration of dopaminergic pathways (43, 47), brain atrophy in strategic reward nodes (24) with impaired incentive processing (33), synergistically acting alpha-synuclein and Alzheimer's disease (AD) protein aggregates and increased burden of vascular and inflammatory changes (48) that may limit the response to the pharmacological treatment (1, 49). Here, SNCA is linked to Alzheimer disease.