A Vest That Allows the Deaf to 'Hear'

Plus other neuroscientific marvels from Dr David Eagleman's lab

Bret S. Stetka, MD


November 17, 2017

As a kid growing up in New Mexico, Stanford University neuroscientist David Eagleman, PhD, suffered a bad fall from a roof. Something about how time seemed to stand still during his descent sparked an interest in neuroscience that would take him beyond the boundaries of the field. As well as research in time perception, his work explores synesthesia, illusions, and what he calls "sensory substitution." This has led him to develop a vest that allows deaf people to "hear" through vibration. Dr Eagleman is a Guggenheim fellow, founder and director of the Center for Science and Law, host of the PBS documentary The Brain with David Eagleman, and best-selling author of numerous book. Medscape recently spoke with him about his work and where the science stands around human perception.

Medscape: Tell me a little about your background and how you got into neuroscience in the first place.

Dr Eagleman: I grew up in Albuquerque, New Mexico. My father is a psychiatrist and my mother is a biologist. So in retrospect, it seems sort of natural that I ended up where I did, but I actually never thought that I would go down this particular path. But back when I was 8 years old, I fell off of a house under construction, and the fall seemed to take a very long time. Later, when I got to high school, I calculated that the fall had only taken around 0.6 of a second. I was really amazed by that. I couldn't figure out why it felt like I'd had so many thoughts during the fall. I've since written many articles on time perception and helped push this area of research forward.

As an undergraduate, I majored in literature but was taking a lot of science. I'd always taken lots of science along the way, but I really loved literature and that's what I thought I was going to go into. But during my last semester I took a neuroscience course and was just completely hooked. I knew that that's what I wanted to do for the rest of my life, so here I am.

For college, I went to Rice in Houston and to Baylor College of Medicine for my neuroscience PhD. The field was so young and there is still so much we don't know. We don't even know the language of the brain. We know that the cells of the brain are all popping off with these little electrical spikes; so a neuron is either on or off, but we don't know the language that's being spoken. In other words, we can listen to the letters of the alphabet, but we don't know the book that's being written, with the 86 billion chattering electrical outlets that are our neuronal connections. We know in the peripheral nervous system that more spikes means harder muscle contractions or bigger stimulus, but what we don't know is anything about how thoughts and desires and concepts are actually stored in the brain and represented, and how they interact with one another.

[W]e can listen to the letters of the alphabet, but we don't know the book that's being written with the 86 billion chattering outlets that are our neuronal connections.

Medscape: It seems like the fact that there's so much unchartered territory in neuroscience is a major draw to the field for many.

Dr Eagleman: Exactly. It's a terrific thing. I mean, presumably in 200 years it might be a boring field! I remember seeing a huge textbook, 1000 or so pages, called Principles of Neuroscience.[1] I thought, these can't all be principles. If they were actually principles of neuroscience, then the book would be five pages long, or a haiku. We really haven't figured out what the principles are yet.

Medscape: Tell us about your graduate work with Francis Crick.

Dr Eagleman: When I got to my post doc at the Salk Institute in La Jolla, California, I began studying how vision and consciousness work. One of my mentors there was Francis Crick, who was the co-discoverer of the structure of DNA. He was also very interested in consciousness. I started doing some studies about consciousness and time perception, and I was able to show in a paper published in Science[2] that what you think you perceive in the moment now has already passed by the time you perceive it. We live in the past. That moment has already gone by. That really launched things for me in this area about perception and consciousness.

Seeing Sound, Feeling Sound

Medscape: You've also done a lot of work in synesthesia, or the phenomenon in which one bodily sense triggers another.

Dr Eagleman: Yes. I just felt like synesthesia is a really interesting road into understanding consciousness. You have two people sitting next to one another; one person has synesthesia and the other doesn't. They're perceiving the world differently. Their conscious experience is different even though almost everything else is the same. I thought that was really fascinating.

When I first got interested in this, most of the papers out there were about one synesthete or maybe a few. I thought, I've got to figure out how to get real numbers here—enough people experiencing this to really help understand it. This was just when the Internet was taking off, and I built this test called the synesthesia battery. I made an online test for synesthesia that's uncheatable. You can only pass it if you actually have synesthesia. Now I've got about 42,000 rigorously verified synesthetes. We know all of their information in terms of exactly, for example, what colors go with certain letters or musical instruments.

I'm happy to say that it is helping revolutionize the field of synesthesia by providing big data in the area. Now we're also working on the genetics of synesthesia and trying to figure out that piece of the puzzle.

You have two people sitting next to one another; one person has synesthesia and the other doesn't. They're perceiving the world differently.

Medscape: An example of synesthesia you hear about a lot is sounds triggering certain visual color perceptions. What are some other examples you've encountered?

Dr Eagleman: When some people hear different chords of music, for example, they feel like they are in different bodily positions—leaping or squatting or things like that. The most common form is where people have what I call spatial sequence synesthesia, in which things like weekdays or numbers have a spatial sense to them. They'll say, "February is over here on my right, and March is next to it, and then April is over here in front of me," and so on. Another common form is where things like letters and numbers have colors associated with them. They trigger an internal color experience. So, for example, you look at J and you think, oh—that's red.

Medscape: Getting back to time perception, what work do you have going on there?

Dr Eagleman: A whole bunch of things. There are all different aspects to our construction of time—things like duration, how long we perceive something to have lasted. This is separate from temporal order, or which thing happened before another, and also from flicker rate, or which thing is flickering faster than the other. All of these things are separable and have illusions associated with them, and can be altered by certain disease states.

A Vest to Help the Deaf 'Hear'

Medscape: You've also developed a vest that allows deaf people to, in a way, "hear" through vibrations. Tell us about this.

Dr Eagleman: It's to hear through vibrations—exactly. The inner ear takes sound and breaks it up into different frequencies; it then sends this information to the brain. I got very interested in the topic of sensory substitution and whether you could actually feed information to the brain via unusual sensory channels. One of my graduate students, Scott Novak, and I ended up making a vest that captures sound and converts it on the fly into patterns of vibration on the torso. In our tests, people can come to understand the world that way. We've now also built a wristband version that has lower resolution but is obviously easier to wear.

We've spun off this research into a company called NeoSensory, in Palo Alto. It's right next to the Stanford campus, where I teach. It's very cool for me because it allows me to explore a different side than just my academic research. Running a company still allows for exciting scientific exploration but with the goal of helping 77 million deaf people.

Medscape: Is this technology available to patients yet? And does it need FDA approval?

Dr Eagleman: At the moment, the FDA has decided not to regulate it because it's noninvasive and harmless. It's just patterns of vibration. Of course, they could always change their minds in the future. We're o working closely with them to make sure that they're aware of what we're doing and vice versa, and it will be available in about 11 months. That's when it's going to finally roll out of the factories. Another part of this that we're really happy about is, for example, if somebody were to get a cochlear implant, that's $100,000 and an invasive therapy. But our wristbands will sell for just $389.

Medscape: Have you tried these on patients yet? Have there been any trials?

Dr Eagleman: Yes. We've demoed this on about 400 deaf people and have done deeper studies on 32. By the time it actually comes out we'll have tested on hundreds more people. The very first deaf person that we put the wristband on started crying because for the first time in his life, he could feel the world. He could hear the sounds—the knocking on the door, and the siren, and the dog barking, and the baby crying, and his wife entering the room.

Neuroscience Meets the Legal System

Medscape: That's amazing. And you're also interested in the intersection of science and the legal system. Tell us about your work in this area.

Dr Eagleman: I'm very interested in the intersection of neuroscience and the legal system, and about how we run our legal policies in relation to science. The bottom line here is that our brains are really different from each other's. People end up in prison for all sorts of different reasons. Some are schizophrenic. Some have other psychopathies. Some are on drugs. There are a number of reasons why people can end up on the wrong side of the law.

Yet we have this notion—and it's the way we've built our legal system—that all brains are created equal and that everyone has the same sort of decision-making capacity. The Center for Science and Law, which I founded, is not trying to let people off the hook but to help our system better acknowledge individual differences. You probably know that America has the highest incarceration rate of any country in the whole world. I think we could be much more effective if we routed people through the system in a way that took into account what's going on inside the skull.

Medscape: A number of developed countries around the world try to provide, say, rehabilitation resources for prisoners with addiction problems rather than simply lock them up. Is this the sort of thing you're talking about?

Dr Eagleman: Yes, exactly—things that actually would qualify as rehabilitative strategies that have meaning. As another example, one thing that I've been pushing very hard for, and which several countries around the world have implemented, are specialized mental health court systems. These are court systems in which judges and jurors are trained in and understand the nuances of mental health. So when a guy comes in with schizophrenia, he's not simply looked at as a guy making things up. Instead, you have people with expertise in what the disease is, what can be done about it, what the legal strategies are. Then you have separate drug courts where you have judge and juries with expertise in drug addiction and rehabilitation. When you have just a single court system, you miss out on the subtleties of what's happening.

Medscape: So, what's next for you?

Dr Eagleman: I have a new book that just came out this week called The Runaway Species; it's about human creativity. It's about why we invented the Internet but squirrels didn't. Why cows don't make it to the moon but we do. If you look across the animal kingdom, all of the functions of brain operation look very similar to ours. Brains are almost the same when you look across different mammals. But we have these slight tweaks that made us this enormously creative species. It essentially has to do with having more cortex and more input and output; we don't just act reflexively and can instead chew on options. If you fly over a forest and look down, the forest looks the same as it did a million years ago. But when you reach a city like New York or Tokyo and look down, it has structures that have risen like a giant motherboard, and it's all due to one species.

So this book is about how human creativity works, what it's about, where it's leading us, and how we can do a much better job in our school systems and in our businesses to leverage creativity. I'm also making an accompanying documentary and have been going around the world interviewing interesting creatives from various fields. I'm very excited.


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