Caffeine is known to confer a number of brain-boosting benefits, but its influence on our ability to store and recall information has never been properly explored. A new study corrects this oversight, showing that caffeine can help us recall certain memories — and it's an effect that lasts for at least 24 hours.
Caffeine is considered a cognitive enhancer on account of its stimulant properties. Though the effects are subtle, it's known to improve mood and mental and physical performance. Studies have also shown that, in conjunction with L-theanine (a common amino acid found in green tea), caffeine can (slightly) boost working memory. But prior to this new study, which was conducted by researchers at Johns Hopkins and the University of California-Irvine, it wasn't known if caffeine has an enhancing effect on long-term memory in humans.
The answer, it would appear, is yes.
To figure this out, the researchers set-up a double-blind experiment in which volunteers who did not regularly eat or drink caffeinated products were administered either a 200 mg tablet (equivalent to a strong cup of coffee) or a placebo. The volunteers were asked to study a series of images — but interestingly, the tablets were taken not before, but five minutes after the study session.
The following day, both groups were tested to see how much information they retained. The test, a behavioral discrimination task, included images from the previous day, but also ones that were slightly altered and some new images altogether. Results showed that members of the caffeine group were able to correctly identify the images as being "similar" to the previously viewed images as opposed to just saying they were identical. It was an effect that lasted for at least 24 hours.
This ability — called pattern separation — allows us to recognize the differences between two similar but not identical items. The researchers say it reflects 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," noted lead author Michael Yassa 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."
Again, it's important to note that the pills were taken after the study session; previous researchers exploring the effects of caffeine on long-term memory had their participants take caffeine before, making it difficult for them to determine if the effect was truly an enhancement, or something driven by other effects of caffeine, like increased attention, vigilance, and focus.
"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. "We report for the first time a specific effect of caffeine on reducing forgetting over 24 hours."
The next step will be to determine the exact brain mechanisms underlying this enhancement — insights that could inform research into neurodegenerative disorders like Alzheimer's.
Read the entire study at Nature Neuroscience: "Post-study caffeine administration enhances memory consolidation in humans."
Image: Dejan Dundjerski/Shutterstock.
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