Lorimer Moseley: Perception and Pain

Lorimer Moseley discusses an intriguing experiment that tricks the brain and demonstrates that perception is always a factor when dealing with pain.

The area that’s important in this is the posterior parietal cortex. It’s not only listening to the primary sensory cortex, but it’s listening to anything else as well—visual, vestibular and auditory—and is very open to attentional modulation.

The posterior parietal cortex is becoming very important for integrating all of the external senses—touch, vision, hearing, taste and smell. The frontal cortex is also involved. There are these loops involved in making things aware—the body’s perception.

How do you know it’s yours?

We can actually do experiments on this. We can make people think they’re outside of their own bodies. They don’t own them anymore. It’s a fun experiment to do.

The one I’ve done more often than others is to get two volunteers who are supposedly normal.

They shake hands. One of the volunteers is wearing a camera on the forehead. The other volunteer is wearing glasses showing him the footage from that camera.

Do you get it?

You’re shaking hands, but your visual field is coming from there, looking back at you. You’re doing the motor command and everything fits. The brain’s predilection to make multiple synchronous inputs fit means your brain very quickly thinks, “Well, yeah, I’m definitely shaking hands. I’m shaking hands with someone who looks horribly like I do.”

You feel like you’re outside of your body.

That’s not your body anymore. If you come in and put a very hot stimulus onto that person’s arm and ask, “Does that hurt?”

“Oh yeah, that hurts.” However, it hurts his arm. It hurts there on his arm, so you’re actually attributing pain to someone else. You’re outside of your own body.

We can use experiments a little bit like that to work out how the brain does this stuff.

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