Their research, published by the journal Nature Neuroscience, shows that caffeine enhances certain memories at least up to 24 hours after it is consumed.
The Johns Hopkins researchers conducted a double-blind trial; 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. 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 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.
The memory center in the human brain is the hippocampus, a seahorse-shaped area in the medial temporal lobe of the brain. The hippocampus is the switchbox for all short-term and long-term memories. Most research done on memory — the effects of concussions in athletics to war-related head injuries to dementia in the aging population — are focused on this area of the brain.
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.
The research is different from prior experiments because the subjects took the caffeine tablets only after they had viewed and attempted to memorize the images.
According to the U.S. Food and Drug Administration, 90 percent of people worldwide consume caffeine in one form or another. In the United States, 80 percent of adults consume caffeine every day. The average adult has an intake of about 200 milligrams — the same amount used in the Yassa study — or roughly one strong cup of coffee or two small cups of coffee per day.