By Crystal Phend
Our self-recognition in the mirror may not be unique, with chimps and maybe some other primates and now dolphins on the short list of those that pass the mirror test.
But although the human brain can correctly interpret the image in the mirror,
it also can be tricked into identifying as "self" things that don’t
exist.
A fascinating set of experiments by behavioral neurologist Vilayanur S. Ramachandran,
director of the University of California San Diego Center for Brain and
Cognition, used mirrors to treat pain in phantom limbs.
A 2009 segment aired on NPR explained how the process worked with one such patient:
One of Ramachandran’s patients complained that he was suffering from
an excruciating cramping in his phantom arm. He felt that his phantom
hand was clenched so tightly, he could feel his fingernails digging
into his phantom palm. The patient was in no way delusional. He knew
his arm had been amputated and that the pain was emanating from a
nonexistent limb. Yet his grasp of this reality was no match for his
perceived pain.Ramachandran came up with
an unusual treatment. He placed a mirror in a cardboard box and
instructed the patient to place his existing hand inside the box, next
to the mirror. When the patient looked down at the mirror, the
reflection of his existing hand stood in as a visual replacement of his
phantom limb. The patient was told to imagine that the reflection was
in fact the lost limb, and to practice clenching and unclenching his
hand while looking in the mirror.To the
patient’s surprise — and Ramachandran’s — the illusion worked. After
two weeks, the patient’s pain vanished, along with his perception of a
phantom arm.
In another experiment, blindfolded patients felt the
researcher poking at the missing limb when their face was touched on
the same side as the phantom, suggesting that the brain had remapped
sensory input to "fill in" the gap after amputation.
So the mirror feedback, though false, feels real to the brain and gets
it to remap correctly in at least some cases. According to another NPR segment with Ramachandran:
"If the patient then starts moving his hand, clapping his hand or
conducting an orchestra or waving goodbye while looking in the mirror,
he’s going to see the mirror reflection of the normal hand superposed
on the phantom, moving in command with the command sent to the phantom
arm," says Ramachandran. "So you’re going to get the visual illusion
that the phantom limb is obeying the command."Though
patients know intellectually that their phantom limbs have not
returned, they are able to successfully trick their brains into
thinking that their limbs have returned."It
not only looks like it’s there, it feels like it’s there," says
Ramachandran. "Patients say, ‘When I move my normal hand, the phantom
arm looks like it’s moving. When I open the normal fist, the phantom
hand — whose fist I could not open for months — suddenly feels as if it
is opening as a result of the visual feedback, and the painful cramp
goes away.’"
Now if only we could figure out a similar way to get the brain to turn
off other kinds of chronic pain … That pain management solution would
truly be the fairest of them all.