Sometimes my mind feels like a beleaguered fishmonger's wife on the dock of my memory calling out to my brain as it wades out to sea.
Have you ever found yourself silently commanding yourself to "Remember to remember to" [insert the minutiae of life here]? It's a kind of meta-recall, and it turns out that it's easier to snatch it from the recesses of the mind when it's associated with other like items.
This brain nagging is called prospective memory and requires two different brain processes depending on what it is you want to recall.
So how do we know this? fMRI of course. In this case researchers from Washington University in St. Louis had study subjects hang out in an fMRI scanner (which measured the blood flow in their brains) while the participants organized words into one of two categories by pushing two different buttons.
In addition, if a special target word in the form of a word or syllable appeared, they had to remember to push a third button.
So what's all this button-pushing about? The key is the target word - the "remembering to remember" act of pushing the button. The target word was either related to or unrelated to the other words the subjects were organizing. And when it was unrelated it required the brain to work with a "top-down" approach, requiring more energy and a different course of neural action, as detected by fMRI.
Of course if the target word were somehow related -- say it was "table" and the other words were tablet and tab -- it was, according to this Popular Science article, "like putting something important near the door so you can't help but see it as you leave." This is perhaps why some things are easier to recall than others.
Which makes me think of the metaphorical opposite, out of sight out of mind, in the form of a boundary event. It's the reason why when you're padding around the house thinking of things you need to do, and then leave one room to go pursue something on your to-do list, you forget what it was you were so feverishly in need of doing.
You, my friend, just experienced a boundary event.
The thing you meant to do is pegged to the physical space you were just in - and crossing that boundary and leaving it behind gives you temporary amnesia until you retrace your steps or will your neurons to serve up the memory.
What to do? Check out this video on building a memory palace. And then start stacking the items on your mental remember-to-remember list by the door.