Forget the memory-boosting pills: In the future, powers of recall could be boosted with programs on a handheld PDA.

Researchers have found a telltale mental signature that predicts whether an experience will be remembered. Once deciphered, the signals could be used to help people know when their brains are primed to remember, perhaps using an iPhone app.

"Instead of looking at how the information is being processed, we're looking at how the brain prepares to process the information," said study co-author Emrah Duzel, a University College, London, neuroscientist. "It may be that the state we look at prepares the memory system for a relevant event."

Duzel's team found the signal in the medial temporal lobe, a region of the brain associated with memory formation. Exactly how medial temporal activation improves recall isn't understood, and researchers have only a vague idea of how memories are stored. As with most of the brain, memory researchers are like Eastern European hackers during the latter stages of the Cold War, trying to connect the mysterious circuitry of western computers to their functions.

Some researchers have found activity in the medial temporal lobe and other memory-processing centers when events are encoded. Other studies have found activation patterns that precede the formation of certain types of memories, such as verbal or visual.

But the new study, in Proceedings of the National Academies of Science on Monday, shows a signal that appears to precede the formation of any memory type. It could be an all-purpose memory switch, determining when the brain enters a favorable encoding state, roughly akin to the overwrite tab on an old-fashioned floppy disk.

"We can't constantly be in a state that's favorable to processing incoming information," said Duzel. "Maybe it's because we need to switch our neural systems beteween incoming information, and information that's already in the brain and needs to be processed further. In that instance, trying to figure out incoming information would disrupt internal processing."

Duzel's team used a magnetoencephalograph to record magnetic fluctuation in the brains of 24 test subjects performing a battery of memory tests. A fraction of a second before test subjects processed a prompt that was later recalled, they displayed heightened levels of so-called theta oscillations.

Theta waves are typically observed during REM sleep and moments of heightened alertness, and localized in the hippocampus — a center of navigational and short-term memory. But Duzel's team traced the oscillations to the medial temporal lobe.

"The fact that you can to some extent predict whether a person is going to remember a word before they've even seen it is quite remarkable," said University of Pennsylvania neuroscientist David Wolk, who was not involved in the study.

Some computer audio programs already offer to tweak brain rhythms, including theta oscillations, with sound. These are unproven, said

Duzel, but a biofeedback approach, in which people can see their brain waves on a computer screen and learn how to control them, could work.

"We could measure the starting state, and then train subjects to enhance that particular amplitude," said Duzel. "When theta activation was high, they'd be more likely to remember information."

The hardware used to record electrophysiological signals is rapidly becoming more mobile, said Duzel.

"There's no reason not to believe that this is possible," he said. "It could be part of a PDA."

Citation: "Medial temporal theta state before an event predicts episodic encoding success in humans." By Sebastian Guderian, Bjorn H.

Schott, Alan Richardson-Klavehn and Emrah Duzel. Proceedings of the

National Academy of Sciences*, Vol. 106, No. 11, March 16, 2009.*

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Image: PNAS

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