Retaining the lessons you have crammed for an exam the next day could be as simple as having a cup of coffee.

A team of researchers in the US has found that a moderate amount of caffeine — the equivalent of that contained in a large mug of coffee — taken shortly after a learning session may help enhance memory performance even after 24 hours.

While the brain stimulant — a key ingredient in coffee bean and also found in many other beverages — is known to fight fatigue and increase attentiveness, it is for the first time that scientists have stumbled upon its ability to consolidate long-term memory.

The findings by scientists, led by neurobiologist Michael A. Yassa at the University of California, Irvine (UCI), may offer yet another reason for drinking coffee. Studies in the past have shown that consumption of caffeine could cut down the risk of dementia or Parkinson’s in old age.

For the study, reported in the journal Nature Neuroscience yesterday, Yassa and colleagues asked over 100 participants to identify images of indoor or outdoor objects. Shortly after that, they were either given 200mg of caffeine or placebo pills. When the participants returned a day later, they were shown some of the same pictures along with random new images and similar-looking images. Though both the groups could correctly identify “old” and “new” pictures, those who had taken the caffeine pill were more accurate at distinguishing “similar” pictures from the original ones. Those who were administered the placebo, on the other hand, incorrectly identified these “similar” pictures as the “old” originals.

Significantly, this caffeine-induced improvement in memory performance was not seen with smaller doses of caffeine or when caffeine was given one hour before the picture identification test. “Our study suggests that a moderate amount of caffeine allows for material studied within a short time window (either before, during or after drinking coffee) to be retained for a longer period of time,” Yassa told KnowHow.

“In addition to the positive effects of caffeine on attention, vigilance and other cognitive factors, it seems to have a specific effect on learning and retention,” he says.

At the same time it doesn’t mean that you should have coffee while sacrificing sleep. “Drinking coffee late at night for the purpose of staying up to study is most likely going to be worse than not drinking coffee at all, as sleep is just as important for memory, if not more important,” notes Yassa.

He says that though his team hasn’t tracked the effects of caffeine on memory for more than 24 hours, there is no reason to believe that it won’t last longer.

More importantly, the scientist says, the type of memory that caffeine enhanced was very specific. “It was memory for specific details that helped the participants (who had the caffeine pill) discriminate between things they saw before or during the study and things they were seeing for the first time (despite the fact that both images were similar),” Yassa explains. “This type of memory, which requires a highly detailed account, was the only memory enhanced. Basic recognition memory was not affected. This was a bit surprising to us,” he remarks.

“This is not a ground-breaking study. What they have done is connected two dots that weren’t connected earlier,” says Abhijit Das, director of neurorehabilitation at the Institute of Neurosciences Kolkata.

Though the scientists haven’t looked into the possible mechanism by which caffeine enhances memory consolidation, they argue that there could be one or more possibilities. One of them could be the blocking of adenosine, a neuromodulator that slows down neural activity and makes you sleepy. The blocking of adenosine, in turn, prevents it from inhibiting the hormone norepinephrine, which is seen to positively influence memory consolidation.

Another theory forwarded by the researchers is caffeine’s action on the hippocampus, the brain region where memories are formed. A study about two years ago by a team of German researchers, which appeared in the Journal of Nuclear Medicine, indicated that in most regular drinkers of coffee, caffeine molecules occupy half the adenosine receptors in the hippocampus and thus effectively reduce the activity of harmful adenosine. This is one of the reasons drinking three to five cups of coffee reduces the risk of Alzheimer’s and Parkinson’s diseases in old age, according to scientists led by David Elmenhorst at the Institute of Neuroscience and Medicine in Germany.