Ever struggled to recall something you knew you ought to remember? Part of the problem might be that your brain just wasn't ready to store the memory in the first place.

Neuroscientists have discovered that how successfully you form memories depends on your frame of mind not just during and after the event in question, but also before it.

"People didn't realize that what the brain does before something happens influences the memory of that event," says Leun Otten of University College London, UK, who led the research. "They looked just at the response."

But it turns out that if your brain is 'primed' to receive information, you will have less trouble recalling it later.

By scanning the brain during these memory tests, the researchers found they could see this priming in action. By watching brain activity they could predict whether the participant would remember a subsequent event, before the event itself had happened.

Surprise test

The participants did not know that their memories were being tested. Instead, they were simply asked to concentrate on a series of single words flashing up on a computer screen. Before each word, a symbol appeared telling the volunteers to decide whether the word represented a living or non-living object, or alternatively whether the first and last letters of the word were in alphabetical order or not.

A few minutes later, Otten's team sprung the surprise memory test on the volunteers, showing them another series of words and asking them to say whether or not they had seen each word before. Throughout it all the volunteers' brain activity was scanned using an EEG (electroencephalogram).

As might be expected, participants were better at remembering words following the living/non-living symbol, rather than the one for alphabetical order. This shows that thinking about the meaning of the words, as opposed to simply looking at the letters, better primes the memory.

Interestingly, the researchers could see this priming activity in the brain's frontal region (where conscious 'thinking' is generally carried out) between the presentation of the symbol and the viewing of the ensuing word. Stronger activity here was followed by more accurate recall. The researchers report their discoveries in Nature Neuroscience.

In another similar test, volunteers were shown symbols telling them whether to expect the next word to be presented to them aurally or on a screen. This time, the memory priming was only evident for on-screen words. "It takes effort and time to redirect the brain from looking at something to listening for something, so it doesn't allow you to get in the right frame of mind," Otten suggests.

The discovery hammers home some old advice for students: that they should really think about things rather than trying to learn by rote. "Always try to focus on understanding what is written; don't just regurgitate," says Otten, because concentrating on meaning is a far better primer for memory.

But setting up your mind for better memory will inevitably be a subtle process, Otten admits, and it's not clear how best to prepare the brain for improved recall. Simple advice might be most effective, however: when reading, try to concentrate rather than letting your mind wander.

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