So I realised that what’s going on here is when you amputate the arm, the part of the cortex of the brain corresponding to the hand is not receiving any signals because you’ve removed the hand. So it’s hungry for sensory input. So what happens is the sensory input from the face skin now invades the vacated territory corresponding to the missing hand, and that then is misinterpreted by higher centres in the brain and arising from the missing phantom hand. And that’s why the patient says, every time you touch his face he says oh that’s my phantom thumb you’re touching, that’s my phantom index finger, that’s my phantom pinkie. In fact you can even put an ice cube on the face and the patient will say oh my thumb is ice cold. You can put a drop of hot water, in fact you put a drop of hot water and the water started trickling down the face, the patient will trace the trickle on his phantom with his normal hand following its path. On one occasion we had the patient raise his phantom and he was amazed to feel the trickle going uphill which is against the law of physics.
Anesthetizing the phantom limb doesn’t always work, but Ramachandran found that tricking the brain might provide a promising alternative. He and his colleagues created a device called the mirror box, in which a patient with a hand amputation, for example, places the existing hand into a slot on one side of the box and a mirror image of it is created on the other side of the box. Both “hands” are visible to the patient, and he or she can then “retrain” the phantom hand to uncurl out of a cramped position or make “normal” movement painlessly, by using the existing hand.
The lesson once again is this: our experiences train our minds and transform our brains, physically. Learning “rewires” us, and new learning has the potential to heal us. Both physical and psychological pain cause changes in the cingulate gyrus, but we can send our brains to boot camp, and retrain them, to try to work against changes that cause chronic suffering. I find this ultimately uplifting. We can’t always avoid pain in our lives, and it may be the worst thing about life, but our work to heal it isn’t always going to be futile, and we have reason to have hope.
Read like an Oliver Sachs story. A woman, plagued for years by an irrestible itch on the back of her head continues to scratch obsessively even after surgeons sever the sensory nerve to her scalp. Institutionalized for seven years, she sleeps in a foam football helmet with her wrists tied to the bedrails.
Along with providing a fascinating detailing of the nature of itching, the article questions the conventional scientific notion that people actually perceive the universe, as it actually exists. Indeed, current theory is more in line with what Irish philosopher Irish philosopher George Berkeley proposed in the 16th century: objects in the world are most likely inventions of the mind.
Scientists discovered that only twenty percent of the fibres connecting with the brain’s visual cortex originate at the retina. The remainder drift downwards from the upper regions, controlling memory and other governing functions According to a prominent British neuropsychologist, Richard Gregory, about 90% of visual perception is determined by memory.
The new theory of perception, in fact, is premised on the concept of the “brain’s best guess’ of what’s happening in the external world, a guess based upon “scattered, weak, rudimentary signals from a variety of sensory channels, information from past experiences, and hard-wired processes, and produces a sensory experience full of brain-provided color, sound, texture, and meaning.”