Growing evidence shows that GM1 ganglioside is involved in amyloid deposition and toxicity. By means of real-time single particle tracking, we show that amyloid oligomers and aggregates formed by Aβ1-42 and amylin, two peptides associated, respectively, with the development of Alzheimer's disease and type II diabetes, interact with GM1 and decrease dramatically its lateral diffusion on the plasma membrane of living neuroblastoma cells. The confinement of GM1, a constituent of membrane rafts involved in neuroprotection, at the level of both types of amyloid aggregates can interfere with cell signaling pathways and contribute to the loss of neuroprotection.