Rare neurological conditions can lead to discovery

I’m not one for pop culture science. I tend to meet media hype around certain scientific topics with resistance, given its history of misinformation and its hasty evolution of speculation into fact (for example, the Refrigerator Mother theory of autism). However, some discoveries reported by the media do seem like they might help us understand and treat illnesses. And as V.S. Ramachandran of the University of California San Diego said in a talk discussing his new book, The Tell-Tale Brain, at the New York Academy of Sciences last Thursday, “media hype does not make these [scientific discoveries] any less important.”

I was first introduced to Dr. Ramachandran’s work by my mother during my first year of studying neuroscience in college. She handed me an article she’d torn out of The New Yorker (abstract here) and insisted that I read it; I was, of course, forced to acquiesce. I wish there was a more eloquent way for me to describe what I thought of his studies, but there isn’t—it was just really, really cool.

The article described his work by giving an example of an unusual case study he encountered some years ago. He met with a man who, while completely rational and intelligent, had a desire to have his perfectly healthy left leg amputated just below the knee. He was and is not alone—apotemnophiles (those who suffer from apotemnophilia) vary greatly in which limbs they wish to have amputated and where specifically along the limb they would like the surgery performed. More surprisingly, roughly a third of them go on to have the limb surgically removed, as Dr. Ramachandran said during his lecture, referencing the same work that The New Yorker article covered.

In the low-tech, personal way for which he is known, Dr. Ramachandran proceeded to formulate a theory about the origin of apotemnophilia based on a series of interviews with people who have the disorder.

“You can learn so much from just talking to the guy,” he said, emphasizing the importance of listening to the patient before sticking him or her into a machine. Based on the sentiments of the people he interviewed, he guessed that the answer might be found in an area of the brain called the insular cortex, or insula. The potential functions of the insula are vast, but this region has been implicated in the formation of bodily self-awareness.

Close your eyes: despite a lack of visual feedback, you know exactly how your body is situated and where your arms and legs are in relation to your torso. The insular cortex might be responsible for this knowledge. Say someone pokes you on your right wrist. The sensory information from the poke is carried from receptors in your skin to areas of your brain posterior to the central sulcus, where the poke is processed. From there, information travels to your insular cortex and is subsumed into your brain’s image of your body. The insular cortex, like the areas posterior to your central sulcus, is topographically organized—there is a specific subarea of each of region that corresponds to a part of your body. (The layout of this organization is known as the homunculus. A diagram showing the amount of brain matter in proportion to each part of the body can be found here.)

However, if you were an apotemnophile who felt the need to have your right arm amputated, the signal heading to your insular cortex would have nowhere to go. Dr. Ramachandran found that in these individuals, the area of the insular cortex that should have corresponded to their undesirable limb was missing. (I should clarify here to prevent propagating any false information: The area was not literally missing. Instead, the neurons that would typically be devoted to those body parts did not respond to sensory input.)

Though this discovery was not a cure or a complete picture, it certainly opened the door to treatments for other problems or disorders people face, like phantom limbs. Many amputees report having sensations in a missing limb long after amputation, a phenomenon known as a phantom limb. For some, the sensation is painful; they sometimes report that the limb is paralyzed in an awkward position. One man who met with Dr. Ramachandran said that he had felt excruciating pain in his phantom limb since amputation ten years earlier. He found that all patients who reported painful paralysis had a severing of nerves in the limb that later became amputated. Prior to amputation, they experienced extreme pain in their unresponsive limbs.

He described the importance of visual feedback and “learned paralysis”: “[The patients] are feeling pain and they’re telling their arm to move but when they look it’s not moving.” The brain learns that the limb is not responding to its commands. This kind of negative visual feedback sustains the feeling of painful paralysis long after the limb has been amputated.

Dr. Ramachandran said he called a colleague to ask how much it would cost to set up a traditional imaging experiment to investigate this effect. “He said it would cost about $20,000. I said, ‘Forget that, let’s try a $2 mirror.’”

In what is perhaps one of his most famous experiments, he used a mirror to train his patient’s brain to unlearn the paralysis. He situated the mirror in front of the man with the reflective surface facing his good arm. Dr. Ramachandran asked him to mimic the position of his phantom with his good hand. When the patient looked into the mirror, he saw his “phantom”—the mirror image of his intact limb.

Dr. Ramachandran then asked him to move his hand into a normal position and wave it around a bit. “He said. ‘Oh my god! You won’t believe it! It’s not paralyzed anymore. The pain is going away!’”

Once the mirror was removed, however, the pain returned—the learned paralysis persisted. But over a series of sessions with the mirror, his brain unlearned the paralysis and the pain subsided until eventually he had no sensations of his phantom limb at all.

Although cases like phantom limbs and apotemnophilia are unique and rare, they are invaluable to the field of neuroscience.

“If I brought a pig in here and said, ‘This pig can talk’ and the pig talked, you wouldn’t say, ‘Well that’s just an n of 1, show me another pig.’ You would say, ‘Oh my god that’s a talking pig!’” said Dr. Ramachandran, illustrating the potential impact of a unique case. Furthermore, while the topics covered in his lecture and in his book certainly don’t represent the larger problems that require the attention of neuroscience researchers (he mentioned this in his self-deprecating way: “It’s not that impressive to the scientific community, making a phantom limb move. It’s a completely useless skill.”), they do lend great insight into the neural underpinnings of basic function. This understanding, in turn, can lead to great advances in neuroscience research, such as the development of brain-linked prosthetic limbs or therapies for paralysis.

Dr. Ramachandran’s work is the stuff of pop culture science, and understandably—it’s simple yet fascinating. But his presentations and publications are science-heavy enough for someone like me to approach them less warily. His studies are an elegant compromise for a businesswoman whose science background consists of two required college courses and her neuronerd daughter.

–Caitlin Schneider

2 responses

  1. Wonderful article. With many troops returning home with severed limbs, Dr. Ramachandran’s work may alleviate the pain they feel and visualize.

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