Our friends at io9 have a great little overview of what we scientific types like to call the Eternal Sunshine Molecules (note: no scientific types call them that.). These are the recently-discovered molecules that may be able to erase, restore, retain, and protect our memories–at least, they might, in the coming decades.
Check out io9’s feature for more on molecules like CaMKII, which leads to the inability to recall short-term memories associated with fear. (Curious about the moral side of that? Check out this ethicist’s position.)