Want To Enhance Long-Term Memory? 2 Espressos, 2 Cups of Coffee or 5 Cups of Green Tea Will Do The Job
Caffeine drinkers generally have higher scores on tests and they usually don't not show any decline in memory throughout the day. A study provides the first convincing evidence that caffeine enhances long-term memory in people -- provided the dose is just right.
What's interesting is that test scores decline significantly between morning and afternoon in people who are regular coffee-drinkers but consumed decaffeinated coffee throughout the day.
At least three quarters of adults over the age of 65 consider themselves "morning" people--meaning they believe that they are at their best in the early hours of the day, compared with less than 10% of younger adults. Ccaffeine can improve memory, which tends to peak in the morning and decline during the late afternoon. But does is important.
Researchers have long suspected that caffeine enhances memory, but studies that tried to show this in people weren't conclusive, as any apparent benefits in memory could have been due to increased attention, a known benefit of caffeine.
Studies in animals such as rats, meanwhile, suggested that it enhances memory consolidation -- the process of strengthening memories between acquiring them and retrieving them -- which should affect long-term memory.
How might caffeine help ward off cognitive decline? "It is a cognitive stimulant," said Karen Ritchie of INSERM, the French National Institute for Health and Medical Research. It also helps to reduce levels of the protein called beta amyloid in the brain, she said, "whose accumulation is responsible for Alzheimer's disease but which also occurs in normal aging."
Michael Yassa, a neuroscientist at the University of California, Irvine, recruited 160 adults who normally consume only minimal amounts of caffeine. The volunteers first studied images of objects, before randomly receiving a pill containing either 200 milligrams of caffeine ( equivalent to two espressos, two cups of coffee or five cups of green tea) -- or a placebo. Receiving the caffeine after studying the images helped to isolate the effect of caffeine on memory, as you wouldn't expect alertness to matter at this point.
When the volunteers returned 24 hours later, they took a memory test involving images they had seen before, unseen images and images that were similar but not identical, such as a seahorse with a different shape to one they had seen previously. The volunteers had to classify these as "old", "new" or "similar".
Yassa's team recorded no differences in accuracy for identifying old or new images between the volunteers who had taken caffeine and those who hadn't -- but this was expected because this part of the task was so easy.
Too Much caffeine
However, the group who had received caffeine were significantly better than the placebo group at identifying which images were "similar" rather than "old", which Yassa says is a harder task.
He concludes that caffeine enhances long-term memory by improving the process of memory consolidation. "This doesn't mean people should only drink coffee after they've studied, and not before," says Yassa. "I think you would get the boost regardless." That's because the process of consolidation is likely to begin as soon as new memories form.
However, caffeine isn't much use once consolidation is finished. The team ran a second experiment in which caffeine wasn't administered until one hour before the memory test, to check for any effects on memory retrieval. They found no such effect. "So let's say you studied without coffee and decided to drink a cup right before an exam -- that's not going to help you retrieve memories better," says Yassa.
Dose Is Essential
Yassa's study also revealed that the dose of caffeine is important. When they repeated the experiment with 100 milligram and 300 milligram doses they found that neither was significantly different from placebo. This could be because other effects kick in at higher doses that negate the benefits for memory consolidation. Also, participants given the 300 milligram dose reported side-effects like jitters and headaches, says Yassa.
Wright's team found a similar effect in bees. "In high concentrations it looks like [caffeine] is bad for learning -- so don't drink too much!" says Wright's colleague Julie Mustard at Arizona State University in Phoenix.