Caffeine enhances long-term memory too

Energy booster for some, waking-up stimulant for others. Now, caffeine stirs another benefit as you prepare that morning cup of tea - enhancing memory.

In a first study of its kind, researchers at Johns Hopkins University in the US have discovered that caffeine has a positive effect on long-term memory in humans.

Michael Yassa, assistant professor of psychological and brain sciences in the Krieger School of Arts and Sciences at Johns Hopkins, and his team found that caffeine enhances certain memories at least up to 24 hours after it is consumed.

"We've always known that caffeine has cognitive-enhancing effects, but its particular effects on strengthening memories and making them resistant to forgetting has never been examined in detail in humans," said senior author Yassa.

"We report for the first time a specific effect of caffeine on reducing forgetting over 24 hours," he added in the study published in the journal Nature Neuroscience.

The participants who did not regularly eat or drink caffeinated products received either a placebo or a 200-milligram caffeine tablet five minutes after studying a series of images.

Salivary samples were taken from the participants before they took the tablets to measure their caffeine levels.

The next day, both groups were tested on their ability to recognise images from the previous day's session, said the study.

The researchers added some new visuals and some images similar to the items previously viewed.

More members of the caffeine group were able to correctly identify the new images as "similar" to previously viewed images.

"If we used a standard recognition memory task without these tricky similar items, we would have found no effect of caffeine," said Yassa.

Using these items required the brain to make a more difficult discrimination - what we call pattern separation, which seems to be the process that is enhanced by caffeine in this case, the study added.

The brain's ability to recognise the difference between two similar but not identical items reflects a deeper level of memory retention, the researchers said.

Until now, caffeine's effects on long-term memory had not been examined in detail. Of the few studies done, the general consensus was that caffeine has little or no effect on long-term memory retention.

According to the US Food and Drug Administration, 90 percent of people worldwide consume caffeine in one form or another.