Recently I read the article
Brain Games by John Colapinto in the New Yorker. It's a wonderful portrait, 13 or so pages long, of V.S. Ramachandran, the father of mirror therapy for phantom limb pain (according to me, at least). It provides the reader with a biographical account of Ramachandran, glimpses into his childhood, how he thinks (like Sherlock Holmes), a window into his personal life (can't remember his wife's birthday, forgets where he parked the car), and an account of his professional trajectory through life, how he ended up with a dinosaur fossil named after him, discussions of his interest in mirror neurons, synesthesia, ichthyology.
Lately he's been studying a patient, dubbed for the article, "Arthur Jamison". I am going to provide excerpts from the article now, direct quotes:
"Jamieson is seventy years old and lives in the Midwest. He is a physician and an amateur cellist, and has been married for forty-seven years. He also suffers from a rare and bewildering condition called apotemnophilia, the compulsion to have a perfectly healthy limb amputated--in his case, the right leg, at mid-thigh."
"After interviewing several apotemnophiliacs--Jamieson is the fifth person with the disorder whom he has studied--Ramachandran was struck by the fact that all of them said they became aware of the compulsion in early childhood, that it centered on a particular limb (or limbs), that they could draw a line at the exact spot where they wanted the amputation to occur, and that they attached little or no erotic significance to the condition. Furthermore, none rejected the limb as "not belonging" to them, as some stroke victims do in the case of a paralyzed arm or leg, and as Ramachandran had predicted they might. Instead, they said that the limb over-belonged to them: it felt intrusive. "If you talk to independent apotemnophiliacs, they say the same bloody things," Ramachandran told me. " 'The line for cutting is here.' 'It started in early childhood.' 'It's over-present.'
They're not crazy.""
"Asked where he would make the cut line for the amputation, Jamieson unhesitatingly drew an index finger across the middle of his right thigh. As to whether he felt that his leg didn't "belong" to him, Jamieson was emphatic. "Somehow, for me, that just doesn't compute, that kind of language," he said. "I have always been fascinated by amputation and wished that I had one. Why? Who the hell knows?"
"Ramachandran and other researchers have shown that the brain is what scientists call "plastic"--it can reorganize itself. Not only are different regions of the brain engaged inongoing communication with one another, with the body, and with the surrounding world; these relationships can be manipulated in ways that can reverse damage or dysfunction previously believed to be permanent. Ramachandran's work with patients at U.C.S.D. has led to one of the most effective treatments for chronic phantom-limb pain and to a new therapy for paralysis resulting from a stroke. (In both instances, his treatment involves only a five-dollar household mirror.) It has also provided suggestive insights into the physiological cause of such mystifying syndromes as autism."
"In the seventies, Michael Merzenich became expert at using microelectrodes to map the sensory cortex of monkeys. In one experiment, he mapped a monkey's hand area in the brain, then amputated its middle finger. Some months later, he remapped the monkey's hand and discovered that the brain map for the missing finger had vanished and been replaced by maps for the two adjacent fingers, which had spread to fill the gap. The results, published in the Journal of Comparative Neurology in 1984, were decisive proof that the brain can reorganize itself--at least across very short distances of one to two millimetres."
"After interviewing Jamieson in his office, Ramachandran led him to a lab for a Galvanic Skin Response, or GSR, test, which would reveal how Jamieson's legs reacted to a mild pain stimulus... David Brang, one of Ramachandran's graduate students, attached a sensor to the middle two fingers of Jamieson's right hand using a Velcro strap. The sensor would measure the reaction of Jamieson's sympathetic nervous system by monitoring the sweat on his fingers. With a sterilized pin, Brang pricked Jamieson's legs at random points, waiting a few seconds between each prick. A scrolling graph on the computer screen registered Jamieson's responses.
The unaffected leg--the left one--and the right leg above where he wished to have it amputated showed a normal response: the graph at first shot upward with each prick, but with further pricks it ceased to rise, then began to flatten out, indicating that Jamieson's nervous system was getting used to the stimulus. But when Brang pricked Jamieson anywhere on the leg below the amputation line, his nervous system responded with increasing distress, the graph climbing higher and higher with each prick.
The experiment seemed to support Ramachandran's theory about the disorder. He believed that people with apotemnophilia had a deficit in the right superior parietal lobule, where the body-image map is assembled. According to this notion, Jamieson was missing the neurons in the map that corresponded to his right leg from the mid-thigh down. He had normal sensation in the unwanted part of his leg--he felt the pin prick. But when the pain signal travelled to the right superior parietal lobule there was nothing in the body-image map to receive it.
"So there's a big discrepancy--a clash--and the brain doesn't like discrepancies," Ramachandran said."When a discrepancy comes in, it says, 'Shit! What the hell is going on here?,' and it kicks in and sends a message to the insular part of the brain, which is involved in emotional reactions--so you're getting this crazy GSR." In apotemnophilia sufferers, the discrepancy causes a feeling of distress that is no less agonizing for being below the level of conscious awareness.
In the past two years, Ramachandran has tested four other apotemnophiliacs using MEG brain scans. "You touch them anywhere in the body and the right superior parietal lobule lights up, as you would expect," Ramachandran said. "But if you touch him here"--he gestured to a point on Jamieson's leg below the amputation line--"nothing happens." Ramachandran said that the experiment needed to be repeated by other researchers, but, he added, "This takes a spooky psychological phenomenon and, as Shakespeare said, gives it a 'habitation and a name.' " Furthermore, the findings suggested to Ramachandran a possible method for alleviating the oppressive sensations in the unwanted limb.
Later, he asked Jamieson to stand in a corner of his office and placed a three foot-high mirror in front of him, in such a way that in place of his right leg Jamieson saw his left, which he held bent at the knee. Jamieson gazed into the mirror. "Astonishing," he said. For a moment, the leg looked "right.""
This is fascinating stuff. I was reminded of reading Michael Gershon's book
The Second Brain, about the gut and enteric nervous system, how if neural crest cells didn't make it in to colonize the large intestine,
Hirschsprung's Disease (Megacolon) is the unfortunate result. So much depends on exquisite timing during embryological unfoldment. Miss one little beat and some batch of baby neurons won't exist, and the resulting human organism can end up with major deficit. It can affect the body, and
maybe, as in the case of Apotemnophilia, one's sensory perception of one's body.
As I checked out
Apotemnophilia online, I saw it was quite consistently coupled with notions of a sexualized nature with heavy overtones of psychiatric implications.
About this, Colapinto writes:
"Jamieson, who was born and raised in New York City, first remembers having an unusual relationship with his right leg when, at around the age of seven, he was waiting for a bus. He found himself thinking that if he stuck out his leg it would be crushed and severed by the bus. "What came to me was not 'No, I don't want to do that' but 'How would I ever explain this?' " he told Ramachandran. In recounting his childhood memories, he said, "One of the things that's astonishing to me is how clear these recollections are."
"These things are very salient," Ramachandran said... "It's interesting to contrast these very clear-cut descriptions with these vague, Freudian notions about this whole phenomenon--that it's primarily connected with sexual stuff."
"Yeah," Jamieson said with disgust. "I've got no desire to cozy up to anyone with a stump. It's psychobabble.""
That it could be due to some embryologic formation error makes more sense. The thigh is actually the last part of the leg to form. Feet (in the form of ectodermic limb buds) poke out first, from the body wall. As toes begin to form, these feet, already containing vasculature and neural structure, begin to lengthen away from the body wall, and the "lines" of supply (vasculature) and communication (nerves) must grow to keep pace. Within the lengthening limb buds, bones begin to condense from cartilaginous masses which have formed from prior condensations of mesoderm; neural and vascular structures must simultaneously penetrate these condensations. Pathways of sensation of a limb to a brain include not just large diameter fibers from skin, but also many sorts of receptors, some very tiny, which report on all sorts of tissue, including vascular tissue (nervi vasorum). Some of these report on the sensory nerves themselves (nervi nervorum). Lots end up just inside the spinal cord, while others get all the way up as far as the insular cortex (1). The brain uses information coming in from many parallel kinesthetic channels(3) as well as visual ones, to construct its sense of self and body awareness/embodiment, to learn who is touching its organism, how it feels about that, what salience to assign in that moment. Apparently some sort of reverse processing occurs between afferents that go to the somatosensory cortex and those that go only to the insula(2). Apparently those going to the left insula are processed differently from those which go to the right (4).
All it would take would be some little screw-up in neural crest implantation into either the limb itself or else at the other end, in the brain itself (it would seem that quite a bit of "peripheral" "nerve", from neural crest, goes all the way into the brain, into some of its very touchy touch processing areas), so I can see how neural crest mishaps could be connected with body perception problems. Perhaps neural crest abnormality might become a target of investigation for body perception disorders some day.
1.
Unmyelinated tactile afferents signal touch and project to insular cortex (Olausson et al.)
2. Unmyelinated tactile afferents have opposite effects on insular and somatosensory cortical processing. (Olausson et al.)
3. Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. (Olausson et al.)
4. Coding of pleasant touch by unmyelinated afferents in humans. (Löken et al.)
