Currently, the predominant theory behind Alzheimer’s disease is the “amyloid hypothesis,” which states that abnormally increased levels of amyloid beta (A?) peptides outside of brain cells produce a variety of low molecular weight A? aggregates that are toxic to the nervous system. These A? aggregates interact directly with target cells and lead to cell death. Scientists are now hunting for the specific mechanisms behind A?-induced toxicity to cells, or cytoxicity.