Scientists at the Innsbruck Medical University discovered that 100 milligrams of caffeine, the equivalent of two cups of coffee, increased activity in the part of the brain that is responsible for short-term memory, and improved performance on a test that measures memory function.

"We found modulation of a distinct brain area within the working memory network was more activated under caffeine compared to the placebo condition. This is the specific brain region which would be used for short-term memory function," said study author Dr. Florian Koppelstatter, a radiology fellow at the university.

These functions include being able to prioritize information to manage tasks efficiently, as well as plan new tasks and deal with stored information, he said. An example would be the process of looking up a number in a telephone book, and remembering it so you could dial the number.

Koppelstatter was to present the findings Wednesday at the Radiological Society of North America's annual meeting, in Chicago.

Caffeine, found in coffee, tea, soft drinks and chocolate, is the most widely used stimulant in the world, with a global, per-person average of 76 milligrams a day. Americans consume an average of 238 milligrams of caffeine daily, which is the equivalent of four-and-a-half cups of coffee. Scandinavians have the highest daily caffeine intake -- 400 milligrams daily, Koppelstatter said.

For the study, Koppelstatter and his colleagues recruited 15 males between the ages of 26 and 47. Over a two-day period that included fasting and no exposure to caffeine or nicotine, each man was given, on alternate days, 100 milligrams of caffeine dissolved in water and then just water. Twenty minutes after taking their drinks, they underwent functional magnetic resonance imaging (fMRI), and then were tested to assess their working memory skills.

The fMRI showed that caffeine increased activity in a brain region in the front lobe, where a part of the working memory network is located, and in the anterior cingulate cortex, the part of the brain that controls attention. None of the men showed an increase in activity in this area of the brain when they drank the placebo.

In an accompanying test, the men were presented with a randomized sequence of capital letters, and they had to decide whether the current letter was the same as or different from the letter presented two letters before. They were asked to respond as quickly as possible by tapping response pads with their fingers.

After consuming caffeine, all the men showed a tendency toward improved reaction times on the test, compared to when they had no caffeine, Koppelstatter said.

"It doesn't mean that without caffeine you don't have activation in this part of the brain, but with caffeine you have modulation of the brain, which means there is more activation," he said.

Dr. Bruce Rubin, a neurologist at the University of Miami School of Medicine, said this study sheds new light on how caffeine works on the brain.

He added that previous research had shown caffeine improves attention, and that any improved memory function identified was assumed to be a result of better focus -- "You have to be attentive to remember."

"But this study showed that caffeine had a direct effect on the networks and processing of the memory," Rubin said.

Koppelstatter said the mechanism by which the caffeine acts on the brain is largely unknown, but is related to the way the substance reacts on the small blood vessels of the brain and on the nerve cells in the brain.

While two cups of coffee might improve your memory, don't think that drinking more will turn you into an intellectual, Koppelstatter noted.

"The positive effects of caffeine don't increase in a linear way," he said, and too much caffeine can make you more anxious, counteracting the positive effects the substance can provide.

By Janice Billingsley - HealthDay Reporter, Wednesday, Nov. 30 (HealthDay News)