美国国家公共电台 NPR Neuroscientists Debate A Simple Question: How Does The Brain Store A Phone Number?

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MICHEL MARTIN, HOST:

About 30,000 brain scientists are meeting in San Diego this weekend. And when neuroscientists meet, it's often the most simple questions that generate the most intense debate. NPR's Jon Hamilton reports on one ongoing¹ controversy². It involves a deceptively simple question. How do we remember a phone number?

JON HAMILTON, BYLINE³: A phone number or any other bit of information we need to keep in mind for just a few seconds. These bits are stored in something called working memory. And Earl Miller⁴ of the Massachusetts Institute of Technology says this type of memory affects just about everything the brain does.

EARL MILLER: Working memory is the sketchpad of your mind. It's the contents of your conscious thoughts. It's how you hold thoughts in mind, how you manipulate them, how you deliberate over thoughts, how you choose when to act or not to act.

HAMILTON: And Christos Constantinidis from Wake Forest University says that's not all.

CHRISTOS CONSTANTINIDIS: Working memory's a core component⁵ of higher cognitive⁶ functions, like planning or language or intelligence.

HAMILTON: The two scientists agree about the importance of working memory, but they disagree about how it works. And, at the Society for Neuroscience meeting, each is presenting research that supports their position. Constantinidis backs what he calls the standard model, which has been around for decades. It says that when we need to remember a phone number, neurons in the front of the brain start firing and keep firing.

CONSTANTINIDIS: And it is this persistent⁷ activity of neurons in the prefrontal cortex that allows you to maintain this information in memory.

HAMILTON: So if those neurons were to stop firing, that number would go away?

CONSTANTINIDIS: Precisely⁸.

HAMILTON: But Earl Miller says it's not that simple. His team used the latest technology to study clusters of neurons in working memory. And they found that, instead of firing all the time, most of these neurons were firing in brief coordinated⁹ bursts.

MILLER: This doesn't sound like a big difference. But, actually, it has a huge functional¹⁰ implications.

HAMILTON: One is that the brain must have some way of retaining the bits of information in working memory between bursts. Miller's explanation is that the neurons are communicating with other parts of the brain, including networks involved in long-term memory. This allows information from working memory to be stored in a latent form, much the way long-term memories are. Miller says that would explain how we can hold onto a phone number, even if we get distracted, momentarily.

MILLER: If you drop your coffee on the way to the phone, you're activity in your brain switches to the dropping of the coffee. But, then, because these memories are stored in latent form, they can be reactivated.

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

MILLER: Well, what it opens up is the most difficult but the most exciting question about working memory, which is volition¹¹, how you gain control of your own thoughts.

HAMILTON: Christos Constantinidis says Miller is correct that working memory neurons do produce rhythmic¹² bursts of activity, but he says the rest is speculation¹³.

CONSTANTINIDIS: The theory's very attractive on theoretical grounds. The problem with the theory is that, so far, there has been no experimental evidence linking this critical variable with behavior.

HAMILTON: Constantinidis says changes in the amount of rhythmic firing don't seem to have much effect on working memory. And he says Miller's contention¹⁴ that working memory is linked to long-term memory just doesn't hold up.

CONSTANTINIDIS: We have clinical cases of patients for whom working memory is profoundly impaired¹⁵. And yet their long-term memory is intact.

HAMILTON: So, for the moment, Constantinidis is standing¹⁶ by the standard model. And he says, during the neuroscience meeting, he'll be taking a skeptical¹⁷ look at the research coming from Miller's lab.

CONSTANTINIDIS: As scientists, that's what we do. We try to poke¹⁸ holes in each other's theories and this debate. I think that's what makes science fun.

HAMILTON: Jon Hamilton, NPR News.