Grafting 101

In a previous post I wrote about how an immersive virtual reality (IVR) system would have to work and how many portrayals in popular television and movies get it wrong. I established that such a system would necessarily be invasive, having to connect itself to every neuron in the peripheral nervous system. Warning: What follows is a rather technical discussion rife with medical and engineering terms.


The crude cables shown in The Matrix, though definitely invasive, do not begin to capture it. To reiterate, every retina cell, every cochlear hair cell, every olfactory sensory neuron, every proprioceptive (joint position) neuron, and every other neuron in peripheral nervous system would have to be freely modulated by such a system. Every channel of sensation would have to be controlled. Anatomically, each of these channels is kept separate until it is highly processed by the brain (separately), and only after each are processed (separately) do specialized areas of the brain integrate them. As a consequence of the channels being processed in parallel, there is no one convergent area that could be targeted or manipulated for the purposes of an IVR system. Thus it has to be the complete peripheral nervous system, i.e. all the neurons comprising the 24 cranial nerves and 62 spinal nerves.


How might this be accomplished? My own idea, while still fanciful and well beyond current technologies, does have a certain conceptual soundness to it. That is, it would work in theory. I call it a peripheral nervous system graft. Rather than a surgically-installed device, the PNS graft would sprout and grow into the body as a synthetic organism. I imagine an genetically-engineered virus that would ‘infect’ peripheral neurons selectively and transform them into syneurons. The syneurons would function identically to and maintain the same connectivity as the cell from which they were born, but would bud and form new connections with a central hub. As the central processor of the device, the hub would implement the control loop that I described previously. I picture it residing somewhere in the abdomen.


Thus, sensory input from the real world would be blocked and simulated reality from the hub would be fed in instead. Likewise, motor output from the brain would be captured and applied to the simulated environment (to a virtual body) and the proxy software would generate whatever motor output it was programmed to do for the real body.

Imagine hanging out with your friends in a virtual club while your proxy does a work-out routine with your body in the real world. You could have virtual feasts on simulated food and return to the real world with an empty stomach. Sound good? Here is where one’s imagination can take off.

There is much more to say about devices such as these, but what is particularly interesting to me are the ethical, moral, and societal implications. My novel delves into just a few of them. It is true that, while theoretically sound, the above is just speculation on my part today, but as we see increased use of mobile computing (smart phones and tablets) and augmented-reality devices (Google Glass), we will begin to grapple with many of these issues.

Immersive Virtual Reality

Imagining how a future technology might work and the implications of such is one of the reasons I enjoy reading and writing sci-fi. That being said, I am often annoyed by wishful and frankly impossible portrayals of technology in many popular movies, shows, and novels. In particular, portrayals of virtual reality technologies are rife with problems. You might just call me a nitpicker, but I’m most interested in what might actually happen in the future and how humans as a species will respond to it.

One blatant example comes to mind: the Holoband in the Battlestar Galactica spin-off series, Caprica. The device is put on and removed as readily as a pair of glasses, and transports the user into a fully-immersive virtual reality. By fully-immersive, I mean it is like being transported to another reality, with its accompanying sights, sounds, smells, sensations, and the ability to move around as you would in reality. The characters using the Holobands are shown climbing stairs, walking through large spaces, riding in aircraft, eating, drinking, getting shot or stabbed, getting in fist fights, having sexual encounters, etc. The problem is that this not only impossible, but absurdly impossible. (Don’t take this as a diss to Caprica. I actually really enjoyed the series and was disappointed it was cut short.)

Let’s talk about immersive virtual reality. To start, I’ll need to launch into a bit of a biology lesson. I’m a neurologist, so you might find the following a bit dense, but I’ll try to make it as interesting and accessible as possible. (It’s okay to skim.)

Inputs and Outputs

Each of us as living things with brains can be viewed as a control loop. The environment around us acts on us (light hits our retinas, sound hits our eardrums, physical objects touch us, etc.), our brain processes this information (sensory input), translates it into a response (motor output), and our bodies act on the environment in turn, thus completing the loop/circuit/cycle. As a requirement, any immersive virtual reality system would have to completely hijack this control loop.


On the sensory input side we have many channels:

  • vision
  • audition
  • olfaction (smell)
  • gustation (taste)
  • rotational/linear acceleration sense (vestibule, saccule, and utricle in the inner ear)
  • somatic sensation (joint position sense, touch, pain, temperature, etc.)
  • visceral sensation (all sensory input from the heart, stomach, intestines, and other internal organs)

Each of these channels can be further broken down into subchannels. To illustrate the complexity, taste, for example, might be the simplest of them all. It can be broken down into specific sensory neurons conveying sweet (sugars, ketones, aldehydes), sour (acid), salty (sodium), savory/umami (glutamate), and a family of 25 taste receptors attuned to chemicals we perceive as bitter. A final receptor that detects lipids (fats) is also believed to exist. Do you agree it’s complex now?

The motor output system consists of all of the motor neurons that emerge from the brainstem and spinal cord, connecting to (innervating) the muscles of the body. (There are neuroendocrine outputs from the brain also, but are not important to this discussion.) The motor nerves can be divided into two groups: somatic (voluntary) and visceral (dealing with internal organs).

Immersive Virtual Reality (IVR) Device

Now that we’ve covered some basic neurobiology, let’s further define how a virtual reality device would behave before we talk about design requirements. For simplicity, let’s say that the device gives the user the experience of being transported to another place in their own body with the ability to walk/talk/interact as he or she would in the real world. The experience would be indistinguishable from the real world or close to it. While using the device, the user’s body would stay in a resting state, preferably sitting or lying on a bed.

For the above immersive virtual reality device to work it must:

  1. capture and replace the user’s sensory input streams from the real world with the simulated virtual ones
  2. capture the user’s motor output streams and simulate appropriate movements of a virtual body
  3. replace the user’s motor output streams with those that maintain the real body in a safe resting state
  4. provide an exit switch in the form of a motor output to leave the virtual world

Before expounding on items one and two, let’s just address the last two quickly. If one is transported to another reality, we don’t want that person to walk around, bumping into things in the real world, as would happen if their motor outputs were allowed to reach the muscles in their real body. On the other hand, we can’t just block the impulses and paralyze the person either, as they would stop breathing and die. For my novel, What a Piece of Work is Man, I came up with the idea of a proxy, essentially a program that controls the body while the user is in the virtual space. It would keep the body in a safe and inert position, and even perform such tasks as exercising, eating, and using the bathroom during prolonged visits to the virtual world. My point is that it is not a trivial problem to keep one’s real body safe while they are in an immersive virtual reality.

Exiting the virtual reality is the other problem. How would the device know when you want to leave? The easiest solution would be for it to monitor your motor outputs for a trigger action or movement. This could take the form of a gesture or verbal command. Dorothy’s tapping her feet together three times and saying “there’s no place like home” would qualify. The point is there has to be a way to readily exit the virtual control loop.

 Capturing and Replacing Human Input and Output Streams–the Nitty Gritty

This is the most difficult part of the whole design and the place where Caprica and The Matrix get it all wrong. Slipping on a Holoband or ramming in a series of wires into your spinal cord will not do the trick. When I talk of capturing the input and output streams of the human brain, I mean literally recording from millisecond to millisecond the exact electrical responses of each of the millions of neurons in each sensory channel. For an immersive virtual reality device to work, this must happen. There are no shortcuts. There is no convergence of the neurons to any one place in the brain, nor can you ‘fudge’ it in any way. And don’t talk to me about using EEGs and functional MRIs. I read EEGs (electroencephalograms) as part of my living, and have kept up with the medical literature on fMRI. Believe me, they will never provide anywhere near the resolution that would be required for this application.

At risk of getting even more technical, the only way to capture the input and output streams  with the necessary fidelity is to have a sensor on or within every neuron. To replace the input and output streams with those corresponding to a virtual reality, the same is true: an actual physical device would have to be present on/within and assume control of every neuron in the peripheral nervous system. Topping it off, to create a coherent IVR experience, each of these millions of sensor/controllers would have to connect to a central processing unit that would run the simulation. That’s some seriously advanced and more importantly, invasive, technology.


How could this be physically possible? This post is already too long, so I’ll get to it in the next one…

Awesome short story

Eliezer Yudkowsky has done some great work in the areas of probability theory, decision theory, and artificial intelligence. (Those are important topics for the coming decades as computers become more powerful, so dig in if you’re interested.) I found recently that he has written an especially clever and well-thought-out short story called Three Worlds Collide. This is probably the best portrayal of mankind making first contact with another intelligent race that I’ve ever encountered. He gives it away for free, so check it out!


Debunking the paleo diet

Fad diets have been a curiosity of mine. This video goes far beyond debunking this particular one. I think it is the most honest and informative talk I’ve ever seen on the past and present of human nutrition.

Alien Life Part I: Biology

As scientific understanding progresses, it gives us a clearer perspective on many things. I really respect sci-fi authors who attempt to stick to the science as much as possible. Far from constraining, I think it gives stories new and interesting turns. Written science fiction has gotten much more believable to me over the years, but I still roll my eyes when I see movies and TV shows portraying alien-human affairs and even hybrid children. As a neurologist, maybe I’m more keenly aware of the ludicrousness of alien biology as it is popularly imagined. Here are a couple things that annoy me—things that are infinitely implausible.

  1. Aliens with DNA. All Earth lifeforms happen to rely on DNA and the related RNA as the molecule of heredity. It seems likely that many other molecules could be just as useful as the templates of life, so why wouldn’t they? Even if life on an alien planet evolved on DNA, the genomes of such creatures would we different, from the molecular machinery of their cells (assuming they have them) to the amino acids and sugars they are composed of (more on that below). Even if the aliens by some 1:10×10^52 chance have identical cellular mechanisms, they would be able to breed with humans only about as successfully as a drosophila fly or an amoeba. So unless your story is going to suggest that humans and an alien race have common ancestry somehow, don’t imply your aliens have DNA! A super-intelligent alien race might decide to engineer their minions after the human genome. What twisted intentions might they have by doing so?
  2. Humanoid aliens or aliens bearing resemblance to an Earth critter. They look just like us only their smaller, skinnier, and gray. Or they all have receding hairlines and funny bumps of different shapes on their foreheads. Or they are just big insects. Inconceivable! For multicellular organisms, embryonic development is like origami. Where folding is concerned symmetry is a property likely to be work on your side, so whatever appendages an alien life form might have, it will likely have a right and left side. More than two sides is possible, but the digestive tract and nervous system ‘construction procedures’ would get tricky for anything much smarter than a starfish. Think about the unique environment in which they evolved. Factors such as gravity, living in air vs liquid, diet, lifespan, reproduction, etc. Come up with something interesting.
  3. Humans dining on alien cuisine or otherwise subsisting on alien plants and animals. It would be very plausible to find water and oxygen on an alien world, but all forms of animal life on Earth require amino acids, sugars, and trace vitamins and minerals in their food. 20 ‘standard’ amino acids are used in accordance with our RNA templates to construct all the proteins that comprise our cells. Of those 20, we must obtain the nine in our diet and we can synthesize the other 11 from them. Would they be found on the alien planet? Unlikely (see above). It turns out it’s not even that simple. All but one of the standard amino acids has a mirror configuration, or enantiomer. (Glycine does not because its mirror is the same.) Nature chose on the the L configuration as the standard and all our enzymes evolved thusly. If you were to visit a parallel universe where Earth’s life evolved according to the D configuration, you would not even be able to digest the grilled chicken there. In fact, it would probably smell and taste like a toxic chemical (since your olfactory and gustatory receptors are also oriented to the L configuration). The same would go for all the plants. Oh, and sugars synthesized by lifeforms on Earth follow the D configuration, so we could have all sorts of fun with the permutations of parallel universes. The take-home message is that if a human is to subsist on an alien planet, they could do so only with technology that would synthesize food from the basic chemical elements. No feasting on the native flora and fauna. If you value your life, it would be best to bring your own lunch to the restaurant at the end of the universe.

In future posts I plan to discuss potential alien neurology, communication, and culture. Stay tuned. . .