Neuroscientists are debating a simple question: how does the brain store a phone number?

You hear the name of a new colleague. You get the directions to the airport. You are looking at a phone number that you are about to dial.

These are the times when you need working memory, the brain's system for temporarily storing important information.

"The working memory is the notebook of your mind; it's the content of your conscious thoughts," says Earl Miller, Professor of Neuroscience at the Picower Institute for Learning and Memory from MIT.

It's also "an essential component of superior cognitive functions such as planning, language or intelligence," says Christos Constantinidis, professor of neurobiology and anatomy at Wake Forest University.

Miller and Constantinidis agree that working memory is essential to everything the brain does. They also agree that working memory problems are a common symptom of brain disorders such as autism and schizophrenia.

But they are poles apart from a heated debate about how working memory works.

Both scientists present evidence in support of their position at the Society for Neuroscience meeting in San Diego this week. They also faced two perspectives in the Journal of Neuroscience in August.

Constantinidis supports what he calls the standard model of working memory, used for decades. It states that when we want to keep new information, such as a phone number, the neurons in the front of the brain begin to fire – and continue to fire.

"And it's this persistent activity of the neurons of the prefrontal cortex that allows you to keep that information in memory," Constantinidis said. If the shooting stops, he says, the memory is gone forever.

But Miller argues that it is not so simple.

His team used the latest technologies to study groups of neurons in working memory. And they discovered that instead of firing persistently, most of these neurons fired in brief, coordinated bursts.

"That does not seem to be a big difference," says Miller. "But in reality, it has huge functional implications."

One of these implications is that the brain must have a way to keep the information in the working memory during activity breaks between bursts.

Miller's hypothesis is that working memory neurons communicate with other parts of the brain, including networks involved in long-term memory. Neurons do this by pulling together at specific frequencies, leaving a temporary "impression" of information in vast networks of brain cells.

The Miller model would allow work memory information to be stored in a latent form, in the same way as long-term memories. And that could explain how we are able to keep a phone number in mind, even if we are distracted momentarily.

"If you drop your coffee on the way to the phone, [the] The activity of your brain goes to the downfall of coffee, "says Miller," but since these memories are stored in a latent form, they can be reactivated. "

If the working memory really interacts with other parts of the brain in this way, it could explain how the areas involved in planning and decision-making are able to control what information remains in the working memory and what is deleted.

"This paves the way, but the hardest but most exciting question about working memory, which is the will," Miller said. "How do you control your own thoughts?"

Miller's working memory model is "very attractive from a theoretical point of view," explains Constantinidis, because he explains some things that are difficult to explain with the standard model. And Miller and others have made an important contribution to the field by detecting activity bursts of working-memory neurons, he says.

"The problem with the theory is that there has been no experimental evidence to date linking this critical variable to behavior," Constantinidis said. And some studies suggest that there is no link.

For example, laboratory experiments suggest that the amount of rhythmic fire does not seem to have much effect on the performance of the working memory.

In addition, Miller's claim that working memory is related to long-term memory seems to contradict the experience of physicians with patients whose brain has been injured, Constantinidis explains.

"We have clinical cases of patients whose working memory is profoundly impaired, while their long-term memory is intact," he said.

So, for the moment, Constantinidis is faithful to the standard model. And he plans to take a skeptical look at the research presented by Miller's lab at the neuroscience meeting.

"As scientists, that's what we do," he says. "We try to make holes in each other's theories, and that's what makes science fun."

For its part, Miller states that a growing number of brain scientists are adhering to his working memory model and performing experiments that will show if he is correct.

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MICHEL MARTIN, HOST:

About 30,000 brain scientists are meeting in San Diego this weekend. And when neuroscientists meet, it is often the simplest questions that generate the most intense debate. Jon Hamilton of NPR reports on an ongoing controversy. This involves a deceptively simple question. How do we remember a phone number?

JON HAMILTON, BYLINE: A phone number or other information that we must keep in mind for only a few seconds. These bits are stored in something called working memory. And Earl Miller of the Massachusetts Institute of Technology says that this type of memory affects just about everything the brain does.

EARL MILLER: The working memory is the sketchbook of your mind. That's the content of your conscious thoughts. It's the way you keep your thoughts in mind, how you handle them, how you deliberate on thoughts, how you choose to act or not to act.

HAMILTON: And Christos Constantinidis of the Wake Forest University says that it's not everything.

CHRISTOS CONSTANTINIDIS: Working memory is an essential component of higher cognitive functions, such as planning, language or intelligence.

HAMILTON: The two scientists agree on the importance of working memory, but they do not agree on how it works. And, at the Society for Neuroscience meeting, everyone presents research that supports their position. Constantinidis supports what he calls the standard model, used for decades. It states that when we have to remember a phone number, the neurons in the front of the brain start to fire and continue to fire.

CONSTANTINIDIS: And it is this persistent activity of the neurons of the prefrontal cortex that allows you to keep this information in memory.

HAMILTON: So if these neurons stopped firing, that number would disappear?

CONSTANTINIDIS: Precisely.

HAMILTON: But Earl Miller says it's not that simple. His team used the latest technologies to study clusters of neurons in working memory. And they found that instead of shooting all the time, most of these neurons were shooting in short coordinated bursts.

MILLER: That does not seem to be a big difference. But, in reality, the functional implications are enormous.

HAMILTON: The first is that the brain must have a way to keep the information in working memory between bursts. Miller's explanation is that neurons communicate with other parts of the brain, including networks involved in long-term memory. This allows the information in the working memory to be stored in a latent form, in the same way as long-term memories. Miller explains that this would explain how we can keep a phone number, even if we are distracted momentarily.

MILLER: If you drop your coffee on the way to the phone, your brain activity goes to the coffee drop. But since these memories are stored in a latent form, they can be reactivated.

HAMILTON: Miller says that if working memory really communicates with other parts of the brain, it could explain one of the great mysteries of neuroscience.

MILLER: Well, what this opens up is the most difficult but most exciting question about working memory, which is the will, how you take control of your own thoughts.

HAMILTON: Christos Constantinidis says that Miller is right in saying that working-memory neurons produce rhythmic surges of activity, but he says that the rest is only speculation.

CONSTANTINIDIS: The theory is very attractive from a theoretical point of view. The problem with the theory is that to date, there has been no experimental evidence linking this critical variable to behavior.

HAMILTON: Constantinidis says that changes in the amount of rhythmic fire do not seem to have much effect on working memory. And he adds that Miller's claim that working memory is tied to long-term memory does not hold water.

CONSTANTINIDIS: We have clinical cases of patients for whom working memory is profoundly impaired. And yet, their long-term memory is intact.

HAMILTON: So, for the moment, Constantinidis is faithful to the standard model. And he says that at the neuroscience meeting, he will skeptically review the research done by Miller's lab.

CONSTANTINIDIS: As scientists, that's what we do. We try to make holes in everyone's theories and this debate. I think that's what makes science fun.

HAMILTON: Jon Hamilton, NPR News. Transcription provided by NPR, Copyright NPR.