Michael Yassa, an assistant professor of psychological and brain sciences at Johns Hopkins University, and his team conducted a double-blind trial in which participants who did not regularly consume decaffeinated products received either a placebo or a 200-milligram caffeine tablet -- equal to about a cup of coffee -- 5 minutes after studying a series of images. Salivary samples were taken from participants before they took the tablets to measure their caffeine levels, and were taken again 1, 3 and 24 hours afterward.
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 those from the day before, some were new additions, and some were similar but not the same.
More members of the caffeine group were able to correctly identify the new images as "similar" to previously viewed images rather than erroneously citing them as the same.
The brain's ability to recognize the difference between two similar but not identical items, called pattern separation, reflects a deeper level of memory retention, the researchers said.
"If we used a standard recognition memory task without these tricky similar items, we would have found no effect of caffeine," Yassa said in a statement. "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 researchers said the study was different from prior experiments because the subjects took the caffeine tablets only after they had viewed and attempted to memorize images.
The finding were published in the journal Nature Neuroscience.