The new data, published in Nature Neuroscience, tested the effect of caffeine intake on post-study memory consolidation in humans, revealing that caffeine intake had a dramatic effect on pattern separation 25 hours after studying images.
Led by Michael Yassa from Johns Hopkins University, the research team noted that until now, caffeine's effects on long-term memory had not been examined in detail - adding that of the few studies done, the general consensus was that caffeine has little or no effect on long-term memory retention.
"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 Yassa.
"Almost all prior studies administered caffeine before the study session, so if there is an enhancement, it's not clear if it's due to caffeine's effects on attention, vigilance, focus or other factors. By administering caffeine after the experiment, we rule out all of these effects and make sure that if there is an enhancement, it's due to memory and nothing else," he explained.
"We report for the first time a specific effect of caffeine on reducing forgetting over 24 hours."
The research team conducted a double-blind trial in which 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. Samples were taken again one, three and 24 hours afterwards.
The next day, both groups were tested on their ability to recognize images from the previous day's study session. On the test, some of the visuals were the same as from the day before, some were new additions and some were similar but not the same as the items previously viewed.
On this test, Yassa and his team found that more members of the caffeine group were able to correctly identify the new images as 'similar' to previously viewed images - versus erroneously citing them as the same.
The team noted that the higher ability to recognise the difference between two similar but not identical items - known as pattern separation - in participants who consumed the caffeine indicates a deeper level of memory retention.
"If we used a standard recognition memory task without these tricky similar items, we would have found no effect of caffeine," explained Yassa. "However, using these items requires 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 our case."
"The next step for us is to figure out the brain mechanisms underlying this enhancement," he added. "We can use brain-imaging techniques to address these questions."
"We also know that caffeine is associated with healthy longevity and may have some protective effects from cognitive decline like Alzheimer's disease. These are certainly important questions for the future."
Source: Nature Neuroscience
Published online ahead of print, doi: 10.1038/nn.3623
"Post-study caffeine administration enhances memory consolidation in humans"
Authors: Daniel Borota, Elizabeth Murray, Gizem Keceli, et al