Researchers at the Medical University Innsbruck in Austria have demonstrated that caffeine boosts short-term working memory.
"We were able to show that caffeine modulates a higher brain function through its effects on distinct areas of the brain," said the paper's lead author, Florian Koppelstatter, M.D., Ph.D.
Dr. Koppelstatter and colleagues used functional magnetic resonance imaging to determine the effects of caffeine consumption on brain activation in a network of modules subserving short-term memory of 15 healthy adult volunteers during a working memory task.
Working memory represents the kind of brain activity required to remember things for a short period of time, according to Dr. Koppelstatter, "like looking up a telephone number in the phone book and storing the number until you've dialed it".
The volunteers were shown a sequence of simple images (the letters A, B, C or D) and then asked if an image was the same as the one shown two images earlier. The volunteers were instructed to respond as quickly as possible using the right index finger for "yes" and the left index finger for "no."
The task was performed after a 12-hour period of no caffeine and a four-hour period of no nicotine exposure.
After receiving 100 milligrams of caffeine (approximately the amount in two cups of coffee), the fMRI showed increased activity in brain regions located in the frontal lobe, where a part of the working memory network is located, and the anterior cingulum, the part of the brain that controls attention.
"What is exciting is that by means of fMRI we are able to see that caffeine exerts increases in neuronal activity in distinct parts of the brain going along with changes in behavior," Dr. Koppelstatter said.
Caffeine is currently the most widely used stimulant in the world, and is mainly found in coffee, tea, soft drinks and chocolate. Daily caffeine consumption per person averages 76 mg (equivalent to 1 1/2 cups of coffee) worldwide and 238 mg (more than 4 1/2 cups of coffee) in the United States.
Functional MRI is based on the increase in blood flow to the local vasculature that accompanies neural activity in the brain.