Why do memories last or fade?

THAT'S THE WHY:We have all been there, struggling to recall an event, a face or a name, foraging in our brains for some clue about a memory we thought we had filed away. Or maybe there's a mental image you will never shake, no matter how much you might want to.

Why do memories fade or last? Recent research suggests that it involves a protein with the rather unmemorable name protein kinase m zeta (or PKMzeta to be more snappy).

A 2007 study published in Science showed that, in rats at least, if you inhibit PKMzeta and stop it working properly, long-term memories get wiped.

One of the authors, New-York based Todd Sacktor, writes on his website: “. . . inhibiting PKMzeta with a drug caused the erasure of memories that had been learned a day, or even a month before.

“PKMzeta inhibition did not damage the brain and, after the drug had been eliminated, new long-term memories could be learned and recalled.”

On the other hand, switching on PKMzeta in the rat brain appears to strengthen long-term memories, according to another Science study that came out in March this year.

Scientists at UCLA have also been teasing out how a form of PKM underpins long-term memory in brain cells. By blocking the enzyme’s activity experimentally in brain cells from a marine snail, they blitzed a long-term memory in the mollusc.

Co-author of the research, which appeared in the Journal of Neuroscience last month, David Glanzman, said: “Now we can study the cell biology of how PKM maintains long-term memory. Once we know that, we may be able to alter long-term memories.”