Why Not Go for a Head-Transplant?

February 26, 2015

Sounds like a sadistic joke, right? Something that Alice Cooper might sing about. But here’s this Italian neuroscientist who says it’s actually possible. So why not go for a head-transplant?

Lattice roof struts at Tokyo MidTown - July 7, 2013

Lattice roof struts at Tokyo MidTown – July 7, 2013 (Enlarge) Don’t they look a little like neuron fibers?

Suppose you get to be 70 or 80 years old and your mind is fine but your body is all worn out. What can you do? Well, suppose some 20-year-old guy was riding his motorcycle without a helmet. The two of you need to get together! Just take the smart old head and put it on the dumb young body. It’s a win-win solution.

But is it really possible? The main obstacle appears to be connecting the neural fibers in the spinal cord. To this day we have trouble splicing nerve tissue, even though there has been some progress.

OK, but even if you can re-connect severed nerves, I think there’s another major difficulty that people haven’t been talking about very much, and that is: How do you know which nerves to connect to which? You can’t just connect them up in an ad-hoc way, because sensory-motor nerves each have their specific functions.

These nerve fibers are microscopic, of course, and there are a lot of them. Let’s see: Suppose your spinal cord is 12 mm thick in your neck. Well, each axon may be as little as 1 micrometer in diameter. That means you could have maybe 30,000 axons in your spinal cord. I’m bad at math, so I might be wrong here. The spinal cord isn’t all solid axons either. But it looks like there could be 30,000 little wires you’d need to connect up with each other. And again, each wire in the head must be connected to the specific corresponding wire in the body, or else you’ll get seriously messed up.

Imagine what would happen if the Italian doctor connected your axons wrong. You might try to move your finger, but you end up moving your toe instead. You might try to bend your waist, but you end up twisting your knee. It wouldn’t feel like that was your body at all! You’d feel like some evil demon was jerking you around.

The same confusion would happen in the opposite direction, when you sense things. Suppose somebody pinches your toe – you might feel that the person is poking your shoulder. Maybe you stand and put weight on your foot, but it feels like your hand is burning up in a fire! And all this confusion would just be caused by your wires being crossed.

The brain is adaptable of course, so you might eventually reorganize your brain in response to the mixed up spinal cord wiring. Maybe. But I feel pity for you if you have to go through such an ordeal and perform such wrenching brain gymnastics. How long would it take? And that’s assuming you would even survive at all. I hate to think what would happen to your autonomic nervous system …