The causative nature of alpha-synuclein (ɑ-syn) accumulation in Parkinson's disease (PD) pathophysiology has been a subject of debate among researchers, ever since its identification in Lewy bodies. In this episode, experts discuss our current understanding of the role of ɑ-syn in PD, as well as the possibility that the loss of normal ɑ-syn function may be more relevant than the accumulation of insoluble ɑ-syn. We will hear from researchers working to improve the diagnosis and monitoring of PD, with the exciting development of novel ɑ-syn-PET tracers and seed amplification assays that can detect early PD with high sensitivity and specificity.