SNCA and Alzheimer disease: Aggregates comprised of the pre-synaptic neuronal protein, α-synuclein (αsyn), are the major component in Lewy body (LB) inclusions that pathologically define Parkinson’s disease (PD) and Lewy body dementia (LBD) [52, 96]; additionally 40–60% of Alzheimer’s disease (AD) cases display LBs that are most commonly localized to the amygdala [3, 37, 73, 84, 102].