I was telling another writing as I walked into this session, “I must be in the wrong business.” All the psychology talks are much more interesting than the other ones on stem cells and bioterrorism. This morning is Sean Mackey talking about pain perception. This is fascinating stuff. His website is at paincenter.stanford.edu.
Also, if you want to follow other science writers’ Twitters, you can see all Twitters on the conference.
Sean believes that we can’t understand pain by breaking it down into the individual pieces of the experience. It doesn’t lend itself to biological reduction. It’s a complex adaptive system. None of the brain systems that are related to pain are dedicated to pain only – they’re related to emotion, expectation, etc. Plus, pain is subjective. Different people experience pain in different amounts, for the same amount of bodily injury. He particularly uses fMRI to study brain activity in response to pain, which lets us look at brain activity without actually cutting into somebody’s head.
One thing that affects pain perception is attention. When people are distracted by reading a book or listening to music they experience less pain, though this works only to a certain point. High levels of pain don’t respond well to distraction. If we’re anxious, depressed, or afraid, that also affects our perception of pain. There is a really nice episode of WNYC Radio Lab (Placebo) on this – they talk about soldiers in the battlefield experience less pain with hugely traumatic injuries than do middle class business men with the same injuries. After all, think about it, you’re on your way to work and you get hit by a car and get a compound fracture. You’re thinking, “this sucks” If you’re a soldier in the battlefield and you get thrown by a mortar blast and get a compound fracture, you’ve seen your buddies go through much worse. You’re thiking, “I’m alive!”
One of the most interesting things he talked about was our empathy with others’ pain. He told us about a time his son tripped and fell and whacked is head against the wall. He and all the other parents in the room cringed and gasped, but the kid bounced up, just fine. He wondered, did that hurt me more than it hurt my son? It turns out that indeed, our empathy of pain is real. He forgot to warn the squeamish to turn away as he played some video of some terrible sports injuries – feet turned the wrong way, and a leg broken mid-calf. The whole audience cringed and gasped. He asked us, “How many of you FELT that pain?” It turns out that those who don’t just cringe, but actually feel a certain amount of pain in response, tend to be those who have had an injury to that part of the body before. We asked a lot of questions about desensitization to these sorts of images, and he believes that this is an important factor. For instance, surgeons and EMTs, or even children playing violent video games, are in a way trained not to react negatively to these images. In fact, in his own studies, he found one particular volunteer whose brain didn’t light up in the expected way when shown these videos of people in pain. They questioned him further, and found that he was an ex-convict. Interesting!
He also told us about some of his research on the effect of love on the experience of pain. This work is being published, so he couldn’t tell us much at all, but the teaser is that both the experience of pain and the experience of early, intense love, are both connected to our systems of reward (the dopamine systems). They’ve found some interesting connections between these two brain systems. But you’ll just have to wait until he’s published it!
In the Q&A we talked about the role of the anterior cingulate in pain perception. It turns out that people with Obsessive Compulsive Disorder may be treated by cutting the connections to the anterior singulate. People with chronic pain can also be treated this way. When queried, they’ll tell you that they still feel the pain, but they don’t care about it so much. So, the emotional connection to the pain has been cut. This just highlights the fact that pain perception is related to many different brain processes, its a systemic response, and so is very difficult to target. Some of his research has focused on the results of controlling patients’ anterior cingulate response and what that does to pain perception. But again, that’s still in the process of being published. Another interesting tidbit is that people with fibromyalgia (a chronic pain condition) don’t get runner’s high, which is created by our dopamine reward system in the anterior cingulate. Those people have some damage to that reward system. Acupuncture also seems to have some effect on the areas of the brain related to pain perception, which is only partially related to the expectation of reduced pain.