The process of recalling a memory is like a rolling snowball——a trigger provides the first ball, which then rolls through various parts of your brain picking up the additional elements it needs to become a full memory.
The molecule PKMzeta rolls the ball. Actually, when a trigger hits your brain, PKMzeta chooses the paths it takes, allowing it to gather relevant info. And the more frequently you remember something, the more you reinforce these PKMzeta pathways, making the memory easier to access next time. Without PKMzeta, you can roll a snowball and it won't pick up anything.
Now imagine being able to block this PKMzeta exactly when you want. This is what the chemical ZIP does. When researchers injected ZIP into rats, the rats forgot what they'd learned about electrical shocks in the floors of their cages; another injection of ZIP made rats forget a sour taste (perhaps another injection would help the rats forget why they're pissed off at the researchers).
With more work, ZIP could make you forget to smoke when you sit at a bar, forget the traumatic memory of seeing the movie Spice World, or forget the time many years ago that you were savaged by that evil ventriloquist dummy.
But given the opportunity, which memories should we block? Traumatic as it was, aren't we better off remembering our dread of Spice World so that we can adjust our future behavior? And couldn't removing memories also wipe out our morality and conscience, developed over years of remembering the consequences of our actions?
Here's a little experiment. First close your eyes. Wait, that's not going to work. Okay, open your eyes. And think about the place at which you're most at peace. Mmmmmm. Go to this special place. Mmmmmm. Okay, maybe now you can close your eyes for a bit. Now quick! Open your eyes and look at the cover of my new book (at left). It's almost like you can't resist buying Brain Candy, right?