The new system seeded with misfolded α-synuclein has 2 fixed points: (1) one represents the scenario in which misfolded α-synuclein dies out, cleared by metabolic mechanisms before being able to transmit the infection to the entire population; (2) the other represents a major outbreak of misfolded α-synuclein, spreading to other regions via physical connections, causing further misfolding of endogenous α-synuclein and widespread propagation (see S1 Text and S1 Fig). The gene discussed is SNCA; the disease is infection.