Future recall

Imagine your next vacation. You are relaxing on a beach, waves lapping at the shore, a cool breeze wafting through the trees and the sun caressing your skin. Fill in the details. What else do you see? Now, remember yesterday's commute. Again, a picture emerges. You are on the train or in your car, or maybe just wandering from your kitchen to your desk. Can you remember what you were wearing? Perhaps you have forgotten that part already.

Without breaking sweat, you can hurtle yourself backwards or forwards in time in your mind's eye - what is known as "mental time travel". One of these visions really happened and the other was fantasy, yet the act of conjuring them up probably felt very similar. It's as if, embedded somewhere in your brain, there is a time machine that can take you forwards and backwards at will.

Neuroscientists and psychologists are starting to think so, too. After more than a century of focusing on just one aspect of mental time travel - remembering the past - these scientists are turning their minds to a bigger question: what if we have been looking at only half the picture? What if the thing we call "memory" works both ways, helping us both recall the past and imagine the future? ...

Researchers have recently started using techniques such as functional magnetic resonance imaging (fMRI) to watch the brain activity of people with fully functioning memories as they remember the past and imagine the future. These studies show something striking and unexpected: as far as the brain is concerned, there is very little difference between the two.

In one such experiment, a team led by Kathleen McDermott of Washington University in St Louis, Missouri, recorded activity as subjects either recalled or imagined a common experience, such as a birthday party, a barbecue or getting lost. McDermott's team expected to see different patterns of brain activity associated with the past and the future - but they didn't. Both tasks produced very similar patterns of activity, with some regions of the brain more activated by future imaginings. Intriguingly, there was no region that lit up only when remembering the past. "We really thought we were going to see a region that was more active in memory than in future thought," says team member Karl Szpunar. "We didn't find that." In other words, episodic memory does not appear to have a specialised brain module dedicated to it, but is handled by part of a universal module for mental time travel (Proceedings of the National Academy of Sciences, vol 104, p 642). ...

•	Future recall New Scientist (UK), Saturday, March 24, 2007 Byline: Jessica Marshall, freelance science writer