by E. Paul Zehr
This cascade is also of concern for other kinds of neuroprostheses like retinal implants for vision and cochlear implants for hearing. An interesting approach to deal with the significant scarring problem for cochlear implants has been to use pharmacological treatments to help trick the nervous system. One such treatment that has shown some promise is to use brain-derived neurotrophic factor (BDNF), which is a major player in a family of chemicals that help in neural development and neural plasticity. In order to avoid the problem of scarring, tissue engineers and nanotechnology experts are working on ways to make the implant appear more biological to the body using means such as this. Even though this pharmacological approach has promise, there is a long way to go to get to a stable enduring implant like that needed for a full brain-machine interface in an Iron Man suit. And then, on top of that, to have the brain subjected to the kind of continual trauma that Tony would experience isn’t really a recipe for long-term success.
Figure 9.4. An example of the cascade of events occurring in the brain after implantation of an electrode array for brain-machine interface. The implantation of an electrode array, known as a Utah array, on the surface of the brain (A). Close-ups of the region right beside the implant (B–D; shown as dashed rectangle in A). Cellular organization in the cortex is shown prior to implantation (B), immediately after implant (“acute,” C), and in chronic implantation (D). Note steadily increasing scarring of support neurons (glia), shown at the far left near the implant surface, and some death of neurons, largely related to inflammatory responses. Courtesy Leach (2010).
Training Keeps Tony’s Brain from Getting Rusty
A big part of thinking about Iron Man’s career is his ability to work against the normal decline of nervous system function that happens with aging. Maybe there is some protection from changes in the aging nervous system due to all his training? Biological aging—senescence—is a steady and inevitable process. Senescence captures the reduction in function that starts just around the third decade in humans. Good examples of aging-related changes in the nervous system are those in the motor system. As part of the motor unit concept we talked about earlier, recall that motor neurons in the spinal cord send out their axons to connect with the fibers in your muscles. Well, with aging motor neurons die. Since the motor neurons are the final relays for sending the commands to make muscle contract, it is reasonable to think that muscle strength would decline.
Between the ages of 20 to 90 years, half of the skeletal muscle mass can be lost and this causes a corresponding reduction in muscle strength. Muscle fibers also will die and in particular those in the fastest contracting motor units, the type IIa group. Despite all that going on, you wouldn’t notice the reduction in motor neuron number and muscle fibers that much, because your nervous system has a great ability to cover up problems. Plasticity in the nervous system compensates for the death of muscle fibers and motor neurons in senescence in a very clever way. A large muscle in your leg could have 250 motor units in it, and each unit might connect to a thousand muscle fibers. The distribution is called the “innervation ratio,” and, in this example, would be 1,000. By the time Tony Stark hits age 70, the number of his motor units might drop from 250 to 125 in this muscle. So, he would have lost 125 motor neurons. However, many of his muscle fibers (previously connected to those now-dead motor neurons) would remain alive. They would sit in his muscle waiting to do their normal jobs, and this would happen when other motor neurons innervating muscle fibers in that leg muscle send branches from their axons over to the muscle fibers that are now “disconnected” from their original neurons. This process is called “sprouting” and is similar to the process of sensory reinnervation we talked about earlier with the face transplantation. Overall, this process of sprouting creates much larger innervation ratios—in this example let’s say it is now 1,500 fibers per neuron—and helps maintain strength as you age. This is very similar to what occurs in recovery from some nerve injuries and is affected by how much activity the nervous system sees. So, if Tony is very physically active, his ability to maintain the integrity of his motor system in this way will be improved.
We can extend the example of Tony’s motor system to many other parts of his nervous system. The nervous system is just like all other systems and parts of your body. When not used repeatedly, your physiological systems try to be as efficient as they can be. The nervous system responds to stresses to minimize the effect. You have experienced this throughout your life probably without really paying much attention to it. If you have ever done some strength training, you have a good specific example in mind. Imagine doing a bunch of arm flexion exercises (“biceps curls”). The stress on the muscles doing those curls leads to an increase in strength. Now imagine you did a bunch of training and got stronger but then couldn’t train for a while because you broke your arm (sorry—it is just an example. Nothing personal). Suddenly you wouldn’t be able to use your one arm very much and it would get weaker. You removed the stress now, so your body doesn’t maintain the muscle to the same level. However, because of your training, you had built up a bit of a reserve of muscle strength. You still did weaken when you weren’t able to use your arm, but, the really important part is that you would still finish stronger than if you hadn’t done the training in the first place. So, the training created a kind of reserve that helped buffer the lack of use that occurred later.
Well, you don’t actually curl weights with your brain. But the command to do the curling comes from your brain. Tony Stark is stimulating his brain by straining and training every time he does physical activity or interfaces with his Iron Man suit. He places a lot of extreme demands on his nervous system and creates a kind of “brain reserve” by doing this. Exercise can also stimulate the brain to not only maintain the neurons and synaptic connections but also to create new neurons. Since declining function in the nervous system is inevitable as Tony gets older (and which was really well described in the graphic novel The End from 2010), any reserve he can add will keep a higher function as he gets older.
Brain reserve describes the idea that larger brains with more neurons and more synaptic contacts might be better at dealing with problems during aging, for example, dementia and disorders like Alzheimer’s disease. Cognitive reserve is specific to how brain reserve can affect the ability to think and reason when there is pathological damage to the brain. So, the more reserve you have means the less you will be affected by declines in function. This doesn’t mean Tony Stark could stop the normal inherent decline in function. However, it does mean that he can reduce the impact of the decline. That old phrase of “use it or lose it” applies really well to all aspects of your nervous system!
How Long Will the Iron Avenger Last?
Let’s assume that Tony avoids concussion (or at least too many of them), the bodily rejection of his brain-machine interface, and serious injury from falls and weapons blasts. Let’s also assume that his heart remains healthy and that he keeps his mind in shape to be able to multitask efficiently. What then? When should he fly off to the retirement home for heroes?
In his origin story, we learn that Tony took control of Stark Industries at the age of 21 and that shortly after that had his little “incident” with some shrapnel that put him on the road to inventing Iron Man. Remember that Tony will take more than ten years to go through pilot and hand-to-hand combat training. Remember too that it took Rossy, Nuytten, and Sankai decades to modify their suits and that we allowed 40 years for Tony to go through that process.
If my math is correct, Tony will be in his 60s by the time he masters being Iron Man. Those of you who read Becoming Batman will recall that, using sports icons as a guide, we determined that Batman would have to hang up his cape in his mid-50s, at the absolute latest. So at some point Tony may want to start inventing suits for younger crime fighters to wear. A big caveat, though, is that the estimates for all these timelines are based on thinking of pretty linear and steady progress towards the ultimate objective of Iron Man. But
advances in science and engineering don’t always work like that. There can be wholesale paradigm shifts (like those Thomas Kuhn talked about earlier) and suddenly fields can move forward in big jumps. For Tony Stark’s sake (and for our own imaginations), let’s assume some of those come along during his years of Iron Man research and development. I feel better thinking of Tony as both inventor and user—however short that career as user might be.
The End
The last point of this chapter is that for a real Iron Man suit of armor to exist and to be usefully applied, it must be based on the kind of brain-machine interface hinted at in the Extremis story line. It must respond without having to be consciously commanded. This would free up the neurological resources needed for more challenging tasks and environments. The user must be highly trained and in tip-top shape. Remember, the suit amplifies the user. If the user is “poor quality,” you just get “louder” poor quality when it is amplified. This was pointed out by Whiplash (Ivan Vanko) in Iron Man 2. He was brought in by Justin Hammer to create an army (and navy, and air force, and marines!) of “Iron Man–like” suits for soldiers to wear. But instead he creates remote-controlled robot drones. He tells Hammer “Drone better … human causes problems.” Getting around those problems requires a lot of work still.
We are on a line of discovery that may well one day produce what was written on the Invincible Iron Man masthead beginning with issue #70 in September 1974: “When millionaire industrialist Tony Stark, inventor extraordinaire, garbs himself in solar-charged, steel-mesh armor he becomes the world’s greatest human fighting machine.” Tony’s father, Howard Stark, said it best in one of the old Super 8 film montages shown in Iron Man 2: “everything is achievable through technology.” The fields of neuroscience and biomedical engineering continue to lead efforts to arrive at a useful working concept like that of an Iron Man neuroprosthetic. We aren’t there yet. And certainly the jet boots and repulsor rays are not even on the radar. But much of what we have discussed is on the horizon. We look to the efforts of scientists, engineers, and inventors to continue to take us along that path. The real-life Invention of Iron Man lies ahead.
Appendix
TEN MOMENTOUS MOMENTS OF THE METAL MAN
Iron Man comics have been divided (so far) into five volumes. This does not include the original Iron Man stories in Tales of Suspense. As detailed in Marvel Comics’ Iron Man: The Official Index to the Marvel Universe (2010), Iron Man showed up in Tales of Suspense from his debut in issue #39 from 1963 up until issue #99 in March 1968. Then Iron Man debuted in his own comic from Iron Man #1 in May 1968. This “volume 1” of Iron Man was maintained until issue #332 in September of 1996. Volume 2 spanned Iron Man #1 in November 1996 until #13 in November 1997. Volume 3 began with Iron Man #1 (yes, this is a little confusing) in February 1998 until #89 in December 2004. Volume 4 began as Iron Man #1 (again!) in January 2005 and ran until #32 in October 2008 (although it was called Iron Man: Director of S.H.I.E.L.D. from issue #15). Volume 5 started as The Invincible Iron Man #1 in July 2008. In January 2011, the numbering became consecutive, beginning with #500 to mark the five hundredth issue of the comic. There have also been additional offshoot titles (such as War Machine, which also has several volumes) and special collections across the years.
The ten momentous moments of Iron Man are listed in the table following.
Bibliography
For further reading about the realities of superheroes, have a look at Becoming Batman: The Possibility of a Superhero (Johns Hopkins University Press, 2008). Physics of Superheroes by friendly-neighborhood physics professor James Kakalios (Gotham, 2009) is a great book. If you want further information on Iron Man, I suggest Iron Man: Beneath the Armor by Andy Mangels (Del Rey 2008), Iron Man: The Ultimate Guide to the Armored Superhero by Matthew Manning (Doring Kindersley, 2010), or Marvel Chronicle by Tom DeFalco, Peter Sanderson, Tom Brevoort, and Matthew Manning (Doring Kindersley, 2008). An excellent exploration of Iron Man in pop culture is Comic Book Nation by Bradford Wright (Johns Hopkins University Press, 2003). For more on neuroscience, I suggest checking out “Brain Facts,” a primer on the nervous system published and made freely available at www.sfn.org by the Society for Neuroscience. More on brain-machine interface can be found in Beyond Boundaries by Miguel Nicolelis (Times Books, 2011).
COMICS AND GRAPHIC NOVELS CITED
1963
Tales of Suspense #39: “Iron Man Is Born!”
Tales of Suspense #40: “Iron Man vs. Gargantus”
Tales of Suspense #48: “The New Iron Man Battles … the Mysterious Mr. Doll!”
1972
Invincible Iron Man #47: “Why Must There Be an Iron Man?”
1974
Invincible Iron Man #70: “Who Shall Stop Ultimo?”
1979
Invincible Iron Man #121: “A Ruse by Any Other Name”
Invincible Iron Man #122: “Journey!”
Invincible Iron Man #123: “Casino Fatale!”
Invincible Iron Man #124: “Pieces of Hate!”
Invincible Iron Man #125: “The Monaco Prelude”
Invincible Iron Man #126: “The Hammer Strikes”
Invincible Iron Man #127: “… A Man’s Home Is His Battlefield!”
Invincible Iron Man #128: “Demon in a Bottle”
Invincible Iron Man #129: “Dreadnight of the Dreadnought!”
1980
Iron Man #142: “Sky Die”
Iron Man #144: “Apocalypse Then”
1981
Iron Man #150: “Knightmare”
1983
Invincible Iron Man #169: “Blackout!”
Invincible Iron Man #170: “And Who Shall Clothe Himself in Iron?”
1984
Invincible Iron Man #182: “Deliverance”
1987
Iron Man #218: “Deep Trouble”
1989
Iron Man #242: “Master Blaster”
Iron Man #243: “Heartbeaten”
Iron Man #244: “Yesterday … and Tomorrow”
Iron Man #245: “Inside Angry”
Iron Man #249: “The Doctor’s Passion”
1992
Invincible Iron Man #280: “Technical Difficulties”
Invincible Iron Man #281: “The Masters of Silence”
Invincible Iron Man #282: “War Machine”
Invincible Iron Man #284: “Legacy of Iron”
Invincible Iron Man #286: “Dust to Dust”
1993
Invincible Iron Man #290: “This Year’s Model”
Invincible Iron Man #291: “Judgement Day”
2005
Ultimate Iron Man (graphic novel)
Invincible Iron Man: Extremis, Parts 1–4
2006
Invincible Iron Man: Extremis, Parts 5–6
2007
The Invincible Iron Man #10: “Execute Program, Part 4”
Iron Man: Civil War (graphic novel)
Iron Man: Extremis (graphic novel)
Iron Man: Hypervelocity, Parts 1–6
Iron Man / Captain America: Casualties of War #1: “Civil War—Rubicon”
Iron Man: Director of S.H.I.E.L.D. #31: “With Iron Hands, Part 3”
Iron Man: Director of S.H.I.E.L.D. #33: “War Machine, Part 1: Weapon of Shield”
New Avengers: Illuminati #1: “The War with the Kree Is Over”
2008
The Invincible Iron Man #1:“The Five Nightmares, Part 1: Armageddon Days”
The Invincible Iron Man #2: “The Five Nightmares, Part 2: Murder Inc.”
The Invincible Iron Man #3: “The Five Nightmares, Part 3: Pepper Potts at the End of the World”
Invincible Iron Man: The Many Armors of Iron Man (graphic novel)
Iron Man: Demon in a Bottle (graphic novel)
Iron Man: Director of S.H.I.E.L.D.—Haunted (graphic novel)