Alzheimerʹs amyloid story finds its star

β-Amyloid peptides (Aβ) have been genetically implicated as the cause of Alzheimerʹs disease, but the causality of amyloid deposited as plaques has been challenged. The controversial role of amyloid peptides in Alzheimerʹs disease has been highlighted in a recent paper from Lesne and colleagues, who applied Kochʹs postulates to cast a specific memory-deficit-inducing oligomer species as a central player causing memory loss. These authors used a transgenic mouse model to identify a specific type of aggregate that emerges with cognitive deficits and is capable of transmitting a spatial memory defect to unimpaired animals.