6:00am

Mon December 12, 2011
Commentary

Pain and the Sixth Sense

Could backwards thinking actually be beneficial when it comes to treating pain? It might. KUNC commentator Dr. Marc Ringel has more.

The boy who lived across the street when I was growing up was a lot of fun.  He was into games.  We played constantly, everything from chess to Wiffle Ball.  Among the more unusual pastimes-in-a-box I shared with Elliott was a series of tasks you did while watching your hands in a mirror, things like:  tracing a line on a sheet of paper, stacking blocks, and hanging items on a tippy little horizontal bar.

Doing these small tasks with left and right reversed was way more challenging than it seemed it ought to be.  In our ten or so years on Earth the connections between our hands, eyes and brains had already grooved our sense of handedness enough to make us very clumsy at working with a mirror image.

I just read a fascinating report about a medical study that explores how inducing the nervous system to jump its groove might be used therapeutically.  The article, entitled “The analgesic effect of crossing the arms,” appeared in a medical journal called Pain.  (Perhaps not a great read for most.  But subscribers do have the right to tell friends and colleagues about the Pain they get in their mailbox every month.)

The scientists who wrote the report deliberately messed with volunteers’ sense of left and right to see what affect that intervention might have on perceived pain.

Here’s how they did it.  Volunteers sat in a comfortable chair in a silent, temperature controlled room.  They donned laser-proof goggles, earplugs and headphones in order to block out external stimuli as much as possible.

A calibrated laser was aimed at a spot on the volunteer’s wrist.  Intensity was dialed up until the beam stimulated the radial nerve enough to produce a distinct pricking pain.

When pain thresholds were measured with arms uncrossed and crossed the scientists found that it took significantly more energy to make wrists hurt when subjects’ arms were crossed than when they were not.

The theory about why this works is pretty interesting.  It’s based on a sixth sense, which doesn’t generally get the same recognition as the other five.  No, I’m not talking about ESP.  I’m referring to proprioception.  Grounded in receptors in joints, muscles and tendons, proprioception tells your body and its parts where they are in space.

When the researchers hampered subjects’ perception of the surrounding space, by blanking out sight and hearing, and confounded connections with the central nervous system, by crossing limbs from one side to the other, they deprived the brain of some of the data it needed to localize exactly where on the body the hurt was coming from.  This fuzzier proprioceptive signal about the laser assault resulted in less perceived pain when it trickled up to consciousness.

There is huge survival advantage, to paraphrase the Godfather, in getting messages you cannot ignore, and in knowing exactly where they come from.  If you step on a thorn, for example, the pain tells you right away where you’ve been punctured and motivates you to hop on the other foot until you can pull the barb out.  Insults of less distinct origin invoke less perceived hurt because, from an evolutionary perspective, they merit less immediate attention.

Manipulating the body’s sense of itself and the space it inhabits is one of the principles that probably makes massage therapy, chiropractic and acupuncture work.  If researchers can elucidate more of the science behind proprioception, I believe there is great potential to further exploit this sixth sense for healing.

I’ll leave discussion of the other sixth sense, the psychic one, for another day.

 

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