Adrift in the spaces between brain cells are thousands of molecules of a protein called beta-amyloid. Over many decades, the molecules may clump together to form sticky globs that attach themselves like barnacles to the outside of cells.These clumps disrupt the normal function of the neuron, setting off a chain of events that destroys the neuron itself-bringing on the impairments of thinking, memory, and reasoning that characterize Alzheimer's.