Inventing Iron Man (10 page)

What if you decide you want to make a movement? It could be a motion as simple as picking this book up from the bookstore shelf. Or it could be as complex as trying to jump into the air and fly, in true Iron Man fashion. Let's say it was the former, because we can deal with that directly. Also, I don't support you actually jumping into the air and attempting to fly around. As soon as you decided to pick up this book, a command moved through several relays and then finally arrived at the main movement output center of your brain—your motor cortex. This is the home of the neurons that send along the command to activate muscle down into the spinal cord. This part of the motor cortex is right beneath about the topmost part of your skull. You can get a rough idea of where it is by finding the top of your ear and running your fingers up over the topmost middle of the skull and then down the other side. The cells in the motor cortex found under your fingers relay the motor command and are known as the upper motor neurons. They are called this because these motor output neurons are at the physically highest (“upper”) part of the nervous system. After that, the relayed command to move arrives at the spinal cord level (these are the lower motor neurons) for the appropriate muscles.

So that is how you and I and Tony Stark deliberately contract our muscles. But that is just the direct output part. What we also want to understand is how we can detect that activity in the brain related to activating the muscles, but then kind of “short circuit” it so that we can use that brain command to activate a computer or a robot or a motor. Or maybe a computer-controlled, motorized robot (can you say Iron Man?). In so doing, we will answer the question of where the commands to start movement actually come from.

Two other parts of the brain play important roles in the control of movement. These areas are specifically involved in the planning and
coordination of movement and go by the clever names of premotor and supplementary motor areas. Inside your skull, these two areas would be found by locating the middle of your skull as for the motor cortex. Then move your fingers forward about the thickness of two or three fingers and you are into regions right beside the primary motor cortex.

To tackle the question of how we could interface with the brain in order to control machines, we turn to what and how can we get information from brain activity. This brings us to the concept of recording activity from the brain, so our next stop is to understand a little bit about electroencephalography, also known by its initials of EEG. We spoke earlier about Galvani, Volta, and electricity in the nervous system. Here we are talking now about electrical activity in the brain. The activity of all those neurons generates electrical field potentials that can be measured by putting electrodes over the scalp. These noninvasive measures were first discovered by German scientist Hans Berger in 1929, but the concept of electrical activity in the brain was originally described by Englishman Richard Caton in 1875. The thing is that the brain activity, as taken from the EEG signal, changes depending on what you are doing. The size of the activity changes as well as the number of “spikes” that you can see. All of these represent changes in the overall activity of neurons in different parts of the brain. Although it gets a bit complicated, this EEG activity can be filtered and analyzed and then used as a control signal to affect computers and robotic devices. This is called a brain-computer interface and brings us back to the telepresence unit that Tony Stark created for the Iron Man armor. So this part of the Iron Man mythology is already a reality.

You can appreciate the input and output of the brain by actually stimulating the neurons to make them become active. Electrical stimulation over the scalp or on the brain surface can be used. Or, a common research technique (and one that is now used clinically too) is to apply transcranial magnetic stimulation. Conveniently, electrical and magnetic fields are interchangeable, and we can use a magnetic field to activate electrical neurons. This involves using a powerful magnetic coil placed over the part of the brain containing the neurons controlling the muscles you're interested in.

Figure 3.6
shows me sitting in a chair with a magnetic coil placed over my scalp on the left side of my head. Since the pathways for the motor output cross over to the other side of the brain stem and spinal cord, the cells in the left cortex control the muscles on the right side
and vice versa. If I were to make a slowly increasing contraction with my forearm flexor muscles (the ones that pull my wrist in), I would slowly increase muscle activation and force production at the wrist. We can mimic this by steadily increasing the stimulation intensity. Three examples of different intensities of stimulation are shown at the bottom of the figure. You can see how the response of the muscles (called “motor evoked potentials,” or MEPs, and measured with electrodes over those muscles) increases as stimulator output goes up. This shows the clear relation of input and output. We could also basically do the opposite. Instead of stimulating the motor cortex and recording EMG in the muscles, we could record EEG activity from the somatosensory cortex while we stimulated the skin on a body part, resulting in a “somatosensory evoked potential,” or SEP.

In clinical neuroscience, tapping into brain commands for movement has been used to try to help people with certain neurological diseases that affect movement. The terrible disease amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease) is one example. In ALS the lower motoneurons in the spinal cord all progressively die. During this process, the person becomes steadily weaker, is eventually paralyzed, and survives only until the motoneurons controlling the muscles for breathing die. It is one of the most terrifying neurological diseases in my view. The remarkable thing about ALS, though, is that the upper motoneurons, the ones up in the brain that we were discussing earlier, do not die. In fact, ALS doesn't affect any of the cells of the brain. In an attempt to help moderate the effects of the disease, scientists and clinicians can train people who are early into their ALS to use the EEG signal to control a computer cursor.

Making a simple device such as this available to many has been the passion of physician and neuroscientist Jon Wolpaw. Since the early 1990s, Jon and his team at the Wadsworth Center of the New York State Department of Health in Albany have been working on developing a brain-machine interface system based on EEG brain wave activity recorded from the scalp. Recently, this group has developed a brain-machine interface that can be taken into the homes of users. The Wadsworth device is used by people paralyzed in end-stage ALS, and other neurological disorders in which motor control is lost, to communicate by measuring brain activity with a simple stretched cap containing electrodes (embedded into the cap used in clinical EEGs).

Figure 3.6. A transcranial magnetic brain stimulator activating the neurons in my brain that control my right wrist. Each stimulation caused an involuntary twitch of my wrist muscles. This twitch got larger (like trying to contract more forcefully) when the stimulator was turned up higher. Courtesy Richard Carson.

The interface system is used to measure brain activity while the person observes a computer display with items that relate to a standard PC keyboard. The interface then determines which keyboard item the person wants to use. This system can be used to write e-mails and operate any PC Windows-based software that can be controlled by keyboard interface. Currently, this system still requires ongoing intervention and monitoring by experienced support staff, who must come to the user's home and also remotely monitor activity. The Wadsworth group currently focuses much of their efforts on trying to minimize this need for costly technical support.

Currently, some people with ALS who are approaching complete paralysis are using the Wadsworth brain-machine interface. They were able to control a computer interface that allowed them to move a cursor on a screen to select letters to spell words. The idea was that it would be helpful when the disease progressed to the point that they couldn't speak. So they trained the participants how to use the devices when they still had some use of their limbs and then they were well placed to be able to use them in the late stages of the disease.

At the other end of the spectrum, several toy companies are coming up with similar devices with video game controllers. Mattel Mind Flex, NeuroSky, and Emotiv all use scalp electrodes to detect EEG activity to move cursors in games.

The basic concept of a brain-machine interface is essentially replacing the biological signaling connections with technological ones. When damage occurs in the nervous system, such as after a stroke or spinal cord injury, there is interruption in the normal signaling connections from brain to spinal cord that leads to difficulty in muscle activation. As an example of the effect of trauma, let's consider someone who experienced a spinal cord injury in the neck.

The late Christopher Reeve (1952–2004) experienced a horrific spinal cord injury when he was thrown off a horse he was riding. He shattered two vertebrae (the bones of your spinal column) just below his head at the top of the neck. These were cervical vertebrae 1 and 2 (going from top to bottom you have seven cervical, 12 thoracic, and five lumbar vertebrae). Spinal cord injuries are graded in severity
based on the level of the injury (higher is worse because more “downstream” parts of the spinal cord are affected) and how “complete” it is, basically on how damaged is the spinal cord. An injury at the C1-C2 level is often fatal, because it affects the parts of the brainstem that control breathing and cardiovascular function. Christopher Reeve is a tragic example, but he is a good one to think about in a book about a superhero since he played Superman in four major motion pictures from 1978–1987. After his accident, he was required to use a ventilator to breathe and had no functional ability to activate any arm or leg muscles.

If a fully developed brain-machine interface had existed, it could have been used to detect motor signals in Christopher's brain that signaled his intention to pick up an object. Perhaps a glass of something. Or a coffee mug. That would be a typical textbook example. However, I want to use the example of a New York Rangers hockey jersey—I will explain why in a minute. Using a brain-machine interface and a robotic arm, the command to pick up the jersey could be relayed to a computer controlling the robotic arm, and the controller would bring the jersey close to Christopher. As a point of reference, we are nowhere near having anything this complex at present—although researchers have been able to get a monkey to feed itself an orange using this kind of system. An ideal interface would—with no obvious delay or difficulty—take the thought about the action and transform it into actual action.

Now, let me briefly come back to the reason for the New York Rangers jersey. I had the good fortune to meet Christopher Reeve in 2001 at an international spinal cord injury research conference held in Montreal, Quebec. He told us how much he liked the city of Montreal and how, in 1986, during the filming of
Switching Channels
, he wore a New York Rangers jersey to an NHL playoff hockey game between his Rangers and the Montreal Canadiens. Unfortunately for him, but fortunately for legions of Canadiens fans (such as me), the Rangers ran into a very hot, future hall of fame goalie named Patrick Roy and lost. Christopher explained his passion for hockey and his enjoyment of watching playoff hockey between New York and Montreal (two of the “original six” founding members of the NHL). He was presented with a Montreal Canadiens jersey by the conference organizers, which was what spurred the story I just related. So there.

An interesting example of brain-machine interface using implantable electrodes is the CyberKinetics BrainGate. BrainGate's
mission is stated as “advancing technological interfaces in order to help neurologically impaired people continue to communicate with others.” The objective appears to extend to activities including the control of objects in the environment such using a telephone, television, or room lights. The basic BrainGate system includes an electrode sensor that is implanted into the motor cortex and connected to a computer interface that analyzes the recorded neuronal activity. The system simultaneously records electrical activity of many individual neurons using a silicon array about the size of a baby aspirin. That array contains one hundred electrode contacts that are each a bit thinner than a strand of your hair.
Figure 3.7
shows an anatomical model of the head with the electrode array inserted into the brain through a port in the skull. The other end of the cable goes to an interface cable that can go to a computer. The principle of operation is that the neuronal signals from the brain are interpreted and translated into cursor movements. This means the person can control a computer with thought, in a way similar to using wrist movement to shift a mouse to move a cursor. This is close to the concept of the NTU-150 telepresence armor that Tony created way back in 1993. That's where (when?) we go next.