Phantom limb syndrome is caused by a misalignment between our internal body image and the physical body.
John was an aspiring athlete until he lost one of his arms in a car accident. But, though his arm was gone, John continued to feel as though it were still there, even years later. He could wave it around, scrunch his fist in frustration, and even grab objects in the world around him. Once, the author picked up a coffee cup that John was holding in his phantom hand, and John yelped in pain: “Oww! Hey, don’t do that, that hurts!”
John has what’s called a phantom limb. Phantom limbs are like the ghostly memory of an appendage that continues to endure, sometimes for decades, after the physical limb was lost. Most reported cases of phantom-limb syndrome involve an arm or leg, although other phantom appendages – including phantom breasts and phantom erections – have also been reported.
So, what’s the nature of these ghostly appendages?
Well, Lord Nelson, a famous admiral, declared that his phantom arm was direct evidence for the existence of the soul. After all, he claimed, if an immaterial arm can survive the loss of the physical limb, why couldn’t an immaterial form survive the loss of the entire body?
In a sense, Lord Nelson had a point. It turns out, we all have a sort of internal body image that’s distinct from the physical body. For most of us, our body image and our actual bodies are so thoroughly integrated that we tend to take for granted that they’re the same thing– while cases of phantom-limb syndrome show that there is actually a difference. We have good reason to think these phantoms couldn’t survive the total loss of the body – for they’re very much dependent on our brains.
If you look at the surface of the frontal lobe in the brain, you’ll find a vertical strip of tissue called the motor cortex, which is responsible for facilitating movement by sending signals to the muscles. Thanks to magnetic resonance imaging, we know that a representational map of the entire human body is laid out, upside down, on this strip of tissue.
Why do phantom limbs occur? Well, our best explanation is that the area of the brain responsible for controlling the limb continues to send it signals, even after it's gone.
In other words, the representational map and the actual, physical body don’t match up.