Your Brain Absorbs Information, Then Decides To File Or Toss

WASHINGTON - Above your right eye, an inch or so behind your forehead, sits a remarkable slice of brain tissue, about the size of a postage stamp, that serves as a temporary scratch pad for conscious thoughts and feelings.

Known as "working memory," it is where the brain holds pictures, sounds and smells for a few seconds before discarding them or shipping them elsewhere for long-term storage, brain scientists say.

Looking up a phone number, recognizing a face, doing arithmetic or constructing a sentence all involve working memory, also called "short-term memory."

This picture of working memory comes from neuroscientists who are using new tools to study all regions of the brain. They hope their discoveries will lead to a better understanding of mental disabilities and possible treatments for the millions of people who have trouble learning or remembering things.

A recent technique, just coming into widespread use, measures minute changes in the amount of oxygen in blood vessels in the brain. Known as functional magnetic resonance imaging (functional MRI), it lights up areas that are active during some mental processes, such as seeing, calculating or remembering. Researchers can watch which areas switch on and off as people perform different tasks.

A region toward the back of the head glows when your eyes are busy inspecting an object. An auditory section above your ears handles incoming sounds. Other areas light up when you're thinking, talking or moving your feet.

If you decide you want to make a permanent record of something in the scratch pad - say, an unfamiliar face - tiny electrical signals flash through a chain of brain cells, called neurons, toward areas deeper in the brain dedicated to long-term memory. New links between neurons are created or old ones are strengthened in the process.

Permanent storage

When you want to recall the face, signals go back up from long-term memory to working memory.

Transferring information to long-term memory usually involves the left side of the brain, according to Susan Courtney, a researcher at the National Institutes of Mental Health. Dredging it out again happens on the right side.

"These new imaging techniques provide a window into the brain," says Dr. Joseph Coyle, a professor of psychiatry at Harvard Medical School. "For the first time, they permit us to document individual brain functions (and) can lead to drugs and other interventions."

For instance, MRI scans of children afflicted with attention deficit disorder, a problem affecting one out of 20 youngsters in America, show little or no response in their working-memory area, according to Julia Schweitzer, a psychologist at Emory University in Atlanta.

"These kids have trouble taking notes in class or remembering the last paragraph they read," Schweitzer said. "We may be able to find drugs that will help them."

Scientists and pharmaceutical companies are racing to find drugs that will strengthen memory functions.

Working memory is centered in an area known as Area 46, according to neuroscientists. It is one of about 50 sections of the brain that, for convenience, have been assigned numerical labels.

Like a scratch pad, working memory can hold only a limited amount of information - about seven items at a time. Its contents are quickly erased when new information comes in.

As an experiment, read these seven numbers: 7-3-6-9-2-8-5. Repeat them once. Then count back from 99 to 89, two numbers at a time. Now try to remember the original numbers. Chances are the counting task wiped some or all of the digits out of your mind.

Besides single numbers or words, working memory can hold chunks of data, increasing its capacity. A telephone area code, such as 301, counts as a single item. So does a phrase, like "home run" or "breast cancer." The sentence, "Meet me at Joe's place at eight," could equal three chunks.

Patricia Goldman-Rakic, a leading memory researcher at Yale University, said Area 46 is used not only for temporary storage, but also for mental computations and the brain's archive.

Recognition and experience

If you spot a large, round, orange-colored object with black stripes, your eyes report the sight to Area 46. Your working memory fishes around in the files of long-term memory, where such images are stored. You declare: "It's a basketball!"

"Working memory depends on long-term memory - on what we know and what kind of experiences we've had in the past," Joseph LeDoux, a memory expert at New York University, wrote in his 1996 book "The Emotional Brain" (Simon & Schuster).

Working memory also coordinates separate signals coming in from the eyes, ears and nose.

"The way something looks, sounds and smells can be associated with its name in working memory," LeDoux wrote. "Working memory sits at the crossroads of (mental) processing systems and makes high-level thinking and reasoning possible."

Some neuroscientists believe that working memory may also be the seat of human consciousness - a platform that holds whatever a person is aware of at a given moment.

"The stuff in working memory is the stuff we are currently thinking about or paying attention to," LeDoux wrote. "It is likely to be the platform on which a conscious experience stands."