By LEE BOWMAN
SCRIPPS HOWARD NEWS SERVICE

This is your brain. This is your brain on a cafe grande.

For the first time, researchers have been able to watch distinct areas of the brain -- the ones that relate to short-term memory -- fire up after volunteers ingested the equivalent of two cups of coffee.

"Everyone knows coffee makes us more alert, more vigilant, but our study documented how it works in the brain. We were able to show that caffeine modulates a higher brain function through its effects on distinct areas of the brain," said Dr. Florian Koppelstatter, a radiology fellow at the Medical University of Innsbruck in Austria.

Koppelstatter presented the findings Wednesday before the annual meeting of the Radiological Society of North America in Chicago.

Caffeine is the most widely used stimulant in the world, found in coffee, tea, soft drinks and chocolate. Americans, on average, consume 238 milligrams of caffeine (the equivalent of more than 4.5 cups of coffee) each day; worldwide, the per capita consumption is about 76 mg.

Koppelstatter and colleagues used functional magnetic resonance imaging to determine the effect of caffeine consumption on parts of a brain network associated with short-term, or working, memory in a group of 15 healthy male volunteers between the ages of 26 and 47. Some were regular coffee drinkers, others rarely consumed anything caffeinated.

Working memory is the kind of brain activity required to remember things for a short period of time, "like looking up a telephone number in the phone book and storing the number until you've dialed it," Koppelstatter said.

Volunteers abstained from any caffeine for 12 hours before each test. On two separate days, each subject took a capsule that contained either 100 mg of caffeine or a placebo, with researchers switching the dose for each volunteer without letting him know what he was getting.

The men were put inside the MRI scanner shortly before they took the pills while researchers took baseline measurements of their brains. Then, 20 minutes after taking the capsule, they were asked to do a short-term memory task.

"When we subtracted the effects we saw from the placebo studies, there remained significant increases in activity in regions of the frontal part of the brain that control attention and concentration," Koppelstatter said.

He said that while caffeine clearly exerts an effect on normal brain function in the short term, that doesn't mean that the path to superior memory or learning is paved with coffee grounds.

"We still need to learn more about caffeine's effect on mental resources," Koppelstatter said.