SNCA and Parkinson disease: Post-mortem examination of brains affected by neurodegenerative disorders such as AD and Parkinson’s disease demonstrate, through histopathological analysis, pathological changes specifically in the olfactory bulb, including neuron loss and abnormal protein aggregates such as Aβ and alpha synuclein (Attems et al., 2014; Yoo et al., 2018; Arnold et al., 2010).