In other words, prions violate most of biology’s sacred rules. They are one of those annoying reminders of how much we don’t know. (It’s important, I think, to not get too caught up for now in the nomenclature. CPEB might not be a prion in the most literal sense, but it certainly has properties that are prion-esque.) In fact, prion-like proteins in neurons may provide an important key to understanding the mysterious endurance of memory. Take CPEB, this synaptic ingredient that can copy itself, with additional copies serving as an indicator of synaptic strength. Like a prion, this “active” version of CPEB is virtually indestructible. It’s also “infectious,” able to recruit single copies of the protein to join its cut-and-pasting party. Lastly, CPEB seems to be regulated by neural stimulation, so that training fruit flies with a simple learning paradigm triggers the start of the oligomerization, or copying, process. The protein has been flicked on; the synapse has been marked as a memory.