The axon is one of the most crucial elements of a nerve cell. As human beings, we rely on the axon to make sense of the world around us—to feel and make connections between our external and internal environments—and to allow our body to communicate with itself. Through an amazingly well-coordinated regulation of sodium and potassium ions across its membrane, the axon can rapidly generate large potential differences that result in polarised, depolarised, or even hyper-polarised concentration gradients. It is through these electrochemical gradients that information signals can be transmitted around the body in a matter of milliseconds, and various glands and muscles can trigger appropriate responses. The axon, along with the rest of the nerve cell, allows for millions of signals to efficiently pass through different regions of the body every single day; and it is through this intricate artwork of the nervous system that we are able to efficiently coordinate and perform multiple actions at the same time. In other words, the role of the axon simply cannot be emphasised enough.
A couple of years ago, I came across a paper titled, “HEAVEN: The Head Anastomosis Venture Project Outline for the First Human Head Transplantation with Spinal Linkage (GEMINI)” by Dr. Sergio Canavero. After giving a brief history about previous attempts by surgeons around the world at performing head transplantations on monkeys and other animals, Dr. Canavero goes on to describe the surgical procedures he plans on implementing in the surgery. At first glance, I found it hard to fathom the very concept of the procedure. What exactly is a head transplant?
Let’s say we have two individuals, A and B. Assume that A has recently been declared brain dead, but has a perfectly functioning body (i.e. all organs and organ systems are intact and are functioning as they should). Meanwhile, assume that B has a perfectly functioning brain (and head), but their body is suffering from limited muscular growth and function, for example. As a result of this incurable impairment, B is permanently confined to a wheelchair or some other form of mobility support without which they would be unable to lead a normal life. In such a situation, following the consent of B’s family, a head transplantation would involve removing the head of individual B from their body and replacing it with the head of individual A. The outcome would allow for A (or on a more debatable front, the newly created individual C) to have a more mobile lifestyle with a new body and (possibly, until proven) the same personality.
But it really isn’t all that simple. Like Canavero mentions in his paper, the first cephalosomatic exchange was performed all the way back in 1970 by Dr. Robert White on a rhesus monkey. But at the time, there was no technology or knowledge that allowed for the severed regions of the spinal cord to be fused back together. As a result of this, the operation was successful only in terms of establishing a functioning vascular system that could maintain a continuous blood flow between the newly joined head and body. It was after reading more about this procedure that I developed an even greater appreciation for the role of the axon in the body.
Unlike most other cells of the body, mature axonal cells of the central nervous system lose their ability to regenerate upon severance. This is due to the formation of glial scars, which contain several kinds of inhibitory molecules that interfere with cellular regeneration mechanisms in the damaged axonal regions. The key to making the head transplantation procedure a complete success would therefore be to find a substance that can overcome the effects of the inhibitory molecules and promptly facilitate axonal regeneration.
Enter Polyethylene Glycol (PEG). This inorganic polymer, when applied as a topographical solution to the severed regions of the spinal cord, works as a sealing agent and triggers axonal fusion. It turned out to be the magical ingredient in Dr. Canavero’s recipe when he successfully carried out the transplant on a monkey. It was fascinating to learn that the creature actually moved around the room and even made monkey-like noises.
My curiosity for this subject ascended to new heights when I began to dive deeper into the potential outcomes of the surgery. I was particularly interested in the ethical aspects—and the various economical and social factors that stood in the way of this massive scientific breakthrough. I began hosting a series of presentations about my research for different kinds of audiences as I was really keen on discovering what the general public had to say. I could slowly start to see a conflict between science and society, including the elements of religion, politics, and the very law of identity: after all, who is the person who wakes up after the operation?
While the discussions I facilitated through these presentations revolved around all kinds of topics, I think it’s fair to say that all of this wouldn’t have really begun if I wasn’t so fascinated with the power of the axon. When I had to think of a neural structure to make a presentation about for this class, the axon was obviously the one and only thing that came to mind; and although I’ve made a lot of presentations over the last couple of years on the subject of head transplants, I was absolutely thrilled to dive right into it all over again and share my learnings with more people.
In the process of looking at different works of art that revolve around the axon, I found one painting by Lisa Kramer to be particularly interesting. She calls this one Grey Matter and there’s a personal story that lies behind it as well. Following the sad loss of her husband to a stroke, she found creating this piece of art to be a “means of therapy” for her at the time. She says that there are many hidden images within the painting, and a lot to be understood through its “symbolic nature”. For now, as I conclude this blog, I will leave it open to interpretation.
Canavero, S. (2013). HEAVEN: The head anastomosis venture Project outline for the first human head transplantation with spinal linkage (GEMINI). Surgical Neurology International, 4(1), S335-S342. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821155/
Fine Art America. (2011, September 22). Wall Art/Paintings/Brain Paintings/Lisa Kramer. https://fineartamerica.com/featured/grey-matter-lisa-kramer.html
Lodish, H,, Berk, A., Zipursky, S. L., et al. (2000). Overview of Neuron Structure and Function. Molecular Cell Biology, 4(1), Section 21.1. https://www.ncbi.nlm.nih.gov/books/NBK21535/
Wolpe, P. R. (2017). Ahead of Our Time: Why Head Transplantation Is Ethically Unsupportable. AJOB Neuroscience, 8(4), 206-210.