Yael: In today's Moment of Science we're going to play a game called "either/or."      Ready?

Don: Yep.

Y: So, Don, if you were having brain surgery, would you either be out cold, or awake      during the procedure?

D: That's simple . . . I'd be unconscious.

Y: Well, maybe. But more often than you'd think, brain surgeons like to keep their      patients awake during the operation?

D: Really? But isn't it painful?

Y: The patient is numbed up or even knocked out for the cutting into the skull part, of      course. But, as you know, the brain itself has no pain receptors. So, after the brain      has been exposed, the surgeon will often bring the patient back to consciousness.

D: But why?

Y: It's partly because we know so little about the brain. Scientists have a rough sense of      which areas of the brain control functions like speech, hearing, muscle control, and      so on, but there's no really precise map. Which means that a surgeon mucking      around in the brain can easily damage a critical area without knowing it. But if the      patient's awake and reacting to what's happening to his brain, that gives the surgeon      a better sense of what he's doing.

D: For instance . . .

Y: So, for instance, let's say a surgeon is removing a tumor near a part of the brain that      controls speech. If the patient is awake and talking, sudden slurring or difficulty      forming words is a signal that the surgeon should stop and back away.

D: So being awake during brain surgery is really a way to protect the brain.

Y: It may seem strange, but that's the idea.  

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