Head Kick Legend's Scientific Dispatch: Phantom Limbs, Mirrors, and the Complexity of Pain

The reward for fighters like Dan Henderson, and Miesha Tate was victory Saturday night, but they came at a price. Sure, their opponents played their part, but the real price is paid in training: where the body is physically challenged, and stressed in order to simulate the worst that could happen in a fight (and thus be better prepared). This may seem obvious, and inconsequential on the surface, but how many more UFC cards will turn into UFC 108 before we start begging fighters to just play Angry Birds for the last month of camp?

It's easy to envy what fighters do. For those of us who grew up on Bruce Lee, and Jackie Chan, it's fun to fantasize playing the role of 'action hero'. That is, until you've been punched in the face. I don't know what it's like to get hit with a three punch combination, or find myself contorted by a submission, but the power of observation leads me to believe it probably doesn't tickle. How do athletes overcome this physical stress? How do their bodies adapt to the harsh painful environment of mixed martial arts, and contact sports in general? 

First, a word on pain. It's easy to think of pain as having a plus-minus relationship with the body, but it's much more complicated. Pain doesn't operate as "if-then", but more like a vast north and south highway of information: impulses directed from the body's nerve endings (called nociceptors, located all the way up through the top layer of your skin) enter two separate tracts in the spine that affect either the conscious sensation of pain, or the arousal and emotional aspects of pain.

Your body being a product of evolution, the separation is important because it reflects different types of pain: acute pain, which involves specific receptors within the skin that let the brain know when to withdrawal from pressure, distortion, or vibration immediately. And chronic pain: this type of pain is meant to immobilize the affected limb or area so that just enough time is spent in the healing process. It could be said chronic pain is pain that is "learned". But what does this mean, and how do we know? Enter Irene Tracey at the University of Oxford, and her study using lasers to zap the feet of volunteers:

Each zap would hit one of six spots. Some of the spots had already been approved as safe, the subjects were told; others had been approved only with reservation; yet others had not been approved at all because they were susceptible to harm. Asked to pay close attention to how the laser felt, the subjects knew which spot would be zapped next by looking at a monitor as they lay in an fMRI scanner.

In reality, the experiment was entirely safe. Yet the volunteers tended to report that the unapproved spots hurt more than the approved ones. The knowledge they got from the scientists influenced their sensation of pain. The fMRI scans revealed that when the subjects saw they were about to be zapped on an unapproved spot, a region of the pain network called the anterior insula became active. The researchers concluded that the anterior insula was integrating information about the experiment with the sensations from the foot, priming the pain network to feel a little stab.

As pain is processed, so to, are memories of the pain experienced. But can those memories ever be so vivid to your nervous system that they are felt, in conjunction? Even for the layman, this makes sense intuitively. Just think back to your first break-up, or a bad one, and the difficulty of trying to forget even when any potential for a second chance had long since passed. Like a relationship where memories needed to fade but didn't, this is exactly the type of behavior being simulated in the nervous system. As A. Vania Apkarian, a neuroscientist out of Northwestern University, argues:

...the connection between the living memory and the never-ending pain suggests a glitch in the brain. Ordinary pain might turn chronic, he hypothesizes, when inflammation caused by conditions like arthritis or nerve damage provokes an abnormal rush of signals from nociceptors. When these aberrant signals reach the pain network in the brain, Apkarian argues, they overwhelm it. The brain doesn’t get a chance to forget the pain. Instead it learns to feel it continuously.

If pain can be learned...can it be unlearned? Helping identify the mechanisms, I turn to Herman Melville's Moby Dick, who over a century in advance through the character of Captain Ahab, recognized the complexities of pain in referencing the 'soul' that persists in the leg his ocean-dwelling rival ate. This is the observation of Jonah Lehrer in his fantastic book, Proust Was a Neuroscientist, documenting instances where the wisdom of literature preceded the observation of science. I'm talking now, about phantom limbs and the unique experiments used to treat those suffering from phantom limb pain.  

Phantom Limb Syndrome is a bizarre disorder: a disorder that seems divorced from our understanding of human anatomy. But it further emphasizes how pain is processed in so many ways. One of the most curious observations in phantom limbs is how sensation in said limbs can be stimulated by other parts of the body.

For example, why is it that a person with an amputated left arm can sometimes feel sensations in that arm by touching parts of their face (they can also feel 'hot' or cold' depending on the temperature of the beverage being drunk)? The answer lies in the brain, which contains a map of the body. On this map (known as the Penfield Map), the face is next to the arms (the genitals are next to the feet on this map, perhaps explaining why "foot fetishes" in general, and Quentin Tarantino camera shots in particular, are staples of sexual perversions), and the brain continues representing the limb even after it's gone.

One particular scientist came up with an idea to "unlearn" the pain felt in phantom limbs by using a mirror. Since pain involves communication with the brain, perhaps if you tricked the brain, you could trick the body. By creating a mirror box, patients were asked to synchronize movements between one arm (for example), and the other phantom arm in order to create the illusion of movement. These experiments yielded some positive results when some patients felt their paralysis begin to diminish.

Activating this 'spatial confusion' has since been confirmed with other simple techniques: even crossing your arms, as a recent article in the New Scientist revealed. V.S. Ramachandran, the scientist I've been talking about, in documenting the mirror techniques, went even further with these spatial tricks (from his book, the Tell-Tale Brain):

I had the patient, Chuck, looking at the reflection of his intact limb so as to optically resurrect the phantom as before. But this time, instead of asking him to move his arm, I asked him to hold it steady while I put a minifying (image-shrinking) concave lens between his line of sight and the mirror reflection. From Chuck's point of view, his phantom now appeared to be about one-half or one-third its "real" size. (Chuck's response) "It's amazing, Doctor. My phantom not only looks small but feels small as well. And guess what...the pain has shrunk too! Down to about one-fourth the intesity it was before."

Can the experiments used with phantom limbs help athletes with pain in real limbs? I don't know what the statistics look like on deafferentation pain in athletes (defined as "pathological pain" caused by nerve damage), but it is here that MVF (mirror visual feedback) has shown some modest success. Unfortunately the research is limited.

But the progress with or without mirrors continues as scientists continue to learn about the "problem of pain". Mining further from Carl Zimmer's Discover article, a new drug is currently being tested that works by latching on to a specific enzyme associated with chronic pain. Understanding the mechanisms at play will help athletes, as the use of painkillers (a public topic of discussion for fighters like Karo Parisyan and Paulo Filho) can one day be minimized, and so to, can the risks associated with combat sports.