美国国家公共电台 NPR How The Brain Shapes Pain And Links Ouch With Emotion（在线收听）

NOEL KING, HOST:

Hit your thumb with a hammer and you feel physical pain, but the pain is also emotional. That ouch feeling might trigger anger, sadness or even fear. The brain shapes our perception of pain, and learning to control that process may help people with chronic pain. NPR's Jon Hamilton has the story.

JON HAMILTON, BYLINE: When Sterling Witt was a teenager, he developed an ache that wouldn't go away.

STERLING WITT: This low-grade kind of menacing pain that ran through my spine and mostly my lower back and my upper right shoulder blade and then even into my neck a little bit.

HAMILTON: The cause was a severely curved spine. And back then, Witt's reaction to his pain was highly emotional.

WITT: I felt like I was being attacked by this invisible enemy. And it was nothing that I asked for. And I didn't even know how to battle it.

HAMILTON: To make things worse, Witt also struggled with depression and dyslexia. And he often felt like a social outcast. So he channeled his frustration into painting and composing songs.

(SOUNDBITE OF SONG, "PAIN")

WITT: (Singing) Pain, pain, pain is all I ever feel anymore.

I couldn't really read. I couldn't really write. And I wasn't really physically capable. So art and music was ways I could express myself, which was a liberating thing.

HAMILTON: And Witt, who lives south of Kansas City, discovered it could also be an escape from pain.

WITT: When I'm making art and music, I feel less pain. And while I'm doing those things, I'm so distracted from my pain that it's almost like I don't have it.

WITT: Scientists say that's just one way the brain can alter our perception of pain. Karen Davis is a senior scientist at the Krembil Brain Institute in Toronto.

KAREN DAVIS: At its core, pain is just something that hurts or makes you say ouch. And then everything else is the outcome of the pain - how it then impacts your emotions, your feelings, your behaviors.

HAMILTON: Davis says the ouch part of pain begins when something - heat, certain chemicals or a mechanical force - activates special nerve endings.

DAVIS: Once they're activated, they trigger a whole cascade of events with kind of a representation of that signal going through your nerves and into your spinal cord and then all the way up to your brain.

HAMILTON: Then it gets more complicated. Davis says pain signals interact with brain areas involved in physical sensation, thinking and emotion.

DAVIS: There's quite a pattern of activity that permeates through the brain that leads to all the complexities of what we feel associated with that initial hurt.

HAMILTON: Davis says all that processing gives the brain the ability to emphasize or ignore pain signals. Say you're playing hockey and you just got slammed into the boards.

DAVIS: If you're concentrating on that, you're not going to be able to keep skating. Right? So you need to be able to tune out the pain and deal with it later.

HAMILTON: But why does the brain link pain with emotions? To find out, I asked Robyn Crook, a biologist and brain scientist at San Francisco State University. Crook studies the evolution of pain, and she says its most obvious purpose is to prevent or minimize damage to the body. Touch a hot stove and pain tells you to move your hand away - fast. But Crook says evolution didn't stop there.

ROBYN CROOK: In some animals with more complex brains, there's also an emotional or suffering component to the experience.

HAMILTON: In dogs, for example, pain appears to cause emotional distress much the same way it does in people. And Crook says there must be a reason for that. One possibility, she says, involves memory.

CROOK: Having that emotional component linked to the sensory experience really is a great enhancer of memory. And so humans, for example, can remember, you know, a single painful experience, sometimes for their entire lives.

HAMILTON: So they never touch that hot stove again. And Crook says there may be another reason that people and other highly social animals have brains that connect pain and emotion.

CROOK: Experiencing pain yourself produces empathy for other group members or other family members that are in pain such that you can recruit them to help you when you're injured and that you will offer help to them because of the empathetic response to the emotional component of pain.

HAMILTON: That's a good thing. But Beth Darnall, a psychologist at Stanford University, says the link between pain and a person's psychological state can also be destructive.

BETH DARNALL: Mental health disorders amplify pain. They engage regions of the brain that associate with pain processing. And they can also facilitate rumination in fearful focus on the pain.

HAMILTON: And Darnall says, when pain doesn't go away, it can cause disabling changes in the brain.

DARNALL: Pain is really a dangerous signal. But once pain becomes chronic, once it's ongoing, these pain signals no longer serve a useful purpose.

HAMILTON: And over time, they can lead to problems like depression, anxiety and stress. So Darnall has developed techniques that help patients control how the brain processes pain signals. For example, she has a system for teaching pain patients how to slow their breathing and relax their muscles.

DARNALL: This state of relaxation is an antidote to the hardwired pain responses that are automatically triggered by the experience of pain.

HAMILTON: Darnall says techniques like these can provide an alternative to pain drugs, including opioids They can also help pain drugs work better. But Darnall says patients are rarely offered psychological treatments for pain.

DARNALL: We have overemphasized pain as being a biomedical phenomenon that requires a biomedical intervention.

HAMILTON: Sterling Witt, the artist and musician, agrees. He's 40 now and has lived with back pain for more than two decades. But he doesn't take any pain medication. Instead, he stretches and exercises, watches his diet and works hard at staying optimistic.

WITT: I'm actually not convinced that I have to live with this for the rest of my life. I very well may, but at the same time, I live in that state of mind all the time, that there's hope.

(SOUNDBITE OF SONG, "I LOVE YOU MORE EVERYDAY")

WITT: (Singing) Seven, six, five, four, three, two, one more week until I get to see you. These are...

HAMILTON: Witt says it's a state of mind that keeps pain from hijacking his emotions. Jon Hamilton, NPR News.