Scientists say it may be possible to predict how well we will remember something before the event has even taken place.
The brain may need priming to create a memory
By analysing scans, they discovered the brain must get into the 'right frame of mind' to store new information.
For top performance, the brain must mobilise its resources, not only at the moment we get new information, but also in the seconds before.
The University College London research features in Nature Neuroscience.
Previously it was thought that brain activity after an event, not before the event, was key.
Lead researcher Dr Leun Otten said: "It sounds a bit like clairvoyance in the sense that we're able to predict whether someone will remember a word before they even see it.
"Scientists knew that brain activity changes as you store things into memory but now we have found brain activity that tells how well your memory will work in advance."
The UCL team conducted two experiments in which volunteers were given a cue moments before being shown an item.
The cues either gave clues as to how the item should be interpreted, what form it would take, or, in the case of words, how the letters were arranged.
The volunteers were not told to try to memorise the items, and the cues were specifically designed not to nudge the memory.
During the tests, electrical activity in the volunteers' brains was monitored using an EEG (electroencephalogram) scanner.
Tests showed that the brain's electrical activity differed after the cue and before the word was presented.
This was linked to whether the subject would remember or forget the word in a later unexpected memory test.
If the electrical activity maintained a high level over frontal parts of the scalp just before an item was shown, then it was likely that the subject would remember it up to 50 minutes later - and after doing a series of other word tests.
On the other hand, if the voltage was lower, the subjects were less likely to remember the word.
Dr Otten said: "It would be nice to know what brain regions are involved in this preparatory activity, and whether it can be used to help people who have difficulties remembering things.
"Unfortunately we aren't at that stage yet. What we do know though is that it might have something to do with trying to get into the right frame of mind to make a decision about a word's meaning.
"Staying alert between the cue and the word also appears to help. We are currently trying to find out more about this kind of brain activity and how it helps long-term memory."
Professor Ian Robertson, of Trinity College Dublin, told the BBC News website the findings made sense.
He said: "We perceive things faster that we are primed to expect, and this is because the very basic sensory and perceptual processes are tuned by the expectation.
"It makes sense that this happens in memory - that the brain can be more or less prepared or primed to encode a memory."