Associate Professor, Department of Physical Electronics, Tel Aviv University
Breaking the Wall of Blindness. How Neuro Engineering can Relink Brain and Body
I guess I have to complete the sentence. I did not realise that it would be so public, but I had totally different things on my mind back then, so I completely missed this event. I am very, very happy, and very grateful for the opportunity to share this time with you here 21 years later. What I want to do is to expose to you a research topic, which is called neuro-engineering and our contribution to this topic.
Rather than going directly into such strong and somewhat intimidating concepts such as blindness and neuro-engineering, I wanted to start with something calm and beautiful. It has nothing to do with the genes of the orchid; it just has to do with our ability to see it and to appreciate its beauty. The point that I am trying to make here is the fact that vision is an obvious capacity of ours that we rarely actually pay attention to how much ingenuity, if you will, or how much sophistication is involved in such a very basic capacity. On the other hand, if I would ask you to take a picture of an orchid, just like the picture that you see here, you would know, you would appreciate the fact that you need a very, very special camera. You would need fantastic optics: you would need a very, very sensitive film if you use old fashion camera; or you would a need a very, very fancy new chip if you are using a digital camera.
It is really, really important if you want to capture all the different things that you have in this image of the orchid: the different colours, the perception, the contrast. What we often forget is that our eyes are doing this image processing, this image capturing, extremely effectively. The beauty in understanding how our eyes are actually doing these tasks so effectively and so beautifully is apparent when we actually look at how our eye is constructed.
For an engineer, as a physicist, I think it is very rewarding to see that our eye is not very much different from a camera, but it does it in a much, much better way. I think it would take a long time before we can actually build cameras, which are as sophisticated and as clever as our eyes. So, typically, what we are familiar with is just the exterior of the eye and the pupil- this black eye hole- so rich light goes into the eye. But if we look carefully into the eye, what we see is that we have all the different components. We have the shutter, which is really the iris. We have the lens that can change its focal plane so we can look at nearby objects; we can look at far away objects. Then the magic is probably what you could think of as the film or the chip: that is retina. This is a very, very thin layer at the back of our eye, the process that does all the light capturing and processing of information and delivering the information to the brain. It is not by incident that you have these red, green, and blue cells at the back. There are specialised cells that can capture different colours, and they are located right at the centre of our eye. When we are in a darkroom, and the lights are dimmed; the iris opens up just like in a camera: we need to bring in more light. And then at the exterior of our eye, we don’t have this colour sensitivity, and this is when we become effectively colour blind.
It is a beautiful system. Just to demonstrate: so if we have an image, it hits the eye, it hits the retina, and then is delivered to the optic nerve. So it is a beautiful sophisticated system. The trouble, of course, is that a lot of things can go wrong. Each one of these elements, if it doesn’t work properly, is where blindness sets in. One particular and very, very problematic issue is basically the degeneration of these particular cells. This system can remain perfectly fine. Everything else is just in tact, but we lost the capacity to see just because we lost these cells. This is where blindness sets in.
We try to introduce the drama by visualising blindness. Now blindness is something that we all experience every time we close our eyes or every time we turn off the lights. But just to emphasise: blindness is not losing all capacity, but 80% of our activity depends on vision. So it is a very, very dramatic thing. This kind of degeneration that I demonstrated to you is a really prevalent and is a major cause of blindness and, in particular, in aging population. There are cases of degeneration, which are genetic, which occur at relatively young age. But for the most part, it is something that takes place as we age. And, in particular, when we talk about the aging population of Europe, the aging population in some countries in Asia, in the US, it is becoming more and more of an issue, and an issue that as society we have to deal with. The final important comment in that context is the fact that at the moment there is no cure: there is no drug; there is no simple solution that can just resolve this issue.
As engineers, there is a solution; or we believe there is a solution. It may sound as complete science fiction to you, but over the last several decades, several very, very big groups, including, and in particular here, I am showing results from a US group and a very, very successful German team that have produced retinal implants. The idea is very simple. The idea is that we have to replace those photo-sensors, and we have electronic chips that can sense light. So what is the most natural solution is to take these electronic chips with fantastic resolution and introduce them to the back of the eye. It sounds completely crazy, and it would take still a lot of work in order to make this a reality, but it is possible, and it is doable. It was demonstrated that it can restore some vision- at the moment with very limited acuity, but it has been demonstrated.
So the challenge, the remaining challenge, or the wall if we speak in the terminology of this conference, is to do it at high resolution, to do it at the point that we can have such chips readily available, that we have the surgical procedures. From our perspective, from the engineering perspective, we are looking for materials, for methods, how to do it right. Because the important thing to remember is that these devices were not developed intentionally. The device itself was designed intentionally for this particular application, but the technology as a whole was developed for entirely different things. These chips were devised for your computers, for your cellular phones. This is what they are suited for. These are made of typically silicone; they were not designed to be put inside the eye. So the kind of challenges that we have in this field is to find the materials, to find the approaches, to find the engineering how to (this is where neuro-engineering comes about) do this work.
What I am showing you here are some kind of tests that we do in the lab. These are neurons. So, neurons in this particular case are taken from the brains of rats, and we place them on microelectrodes that we build in the lab. You can see that we can visualise them, we can talk with them, and we can work with these cells even though they are very, very small. This electrode that you see now in the background is a 30-micrometre electrode. The round thing there is half the size of the diameter of your hair. It is a very, very small thing. It is very, very possible, readily possible, to take neurons either in the lab setting or in real physiological setting and to communicate- to build the link between electrodes and neurons. Neurons are sensitive to electrical stimulation, and we can do that.
Our specific contribution to this field is to look for materials that can make this link between electronic devices and biology. These are two different worlds. One is soft, made of ions, sensitive to ionic currents. The other one uses electrons, is typically rigid- very, very different worlds. One approach that we have been promoting is to look for a material: in this particular case this is a nanomaterial, carbon nanotubes for those of you who may have heard the term. The carbon nanotubes are basically used as this intermediate material. The reason why we chose this particular material is because neurons like it. That is a very, very critical thing. They just mature, develop, and the picture that you seen on the left- these are two types of brain cells that we have in our brain. They developed and became very, very well attached to the system. If we try to explain, and that is one of our main objectives- to explain to ourselves to understand why do the cells like these surfaces so much. And in very, very juristic terms, it comes about from the fact that they resemble the natural environment that the cells are used to. It is a very rough and porous system.
But these systems, also these carbon nanotubes also have to accommodate the electronics. It also has to be compatible with microelectronics. We had to develop a method that engineers in fabrication facilities can actually go and produce such samples in a very simple way. We have developed an initial system that we can test in the lab and prove to ourselves that these systems are working. But then the next challenge, and that is the important point, is that we also have to make sure that these things are compatible with flexible technology. That was the point where we had to look for entirely different approaches of how to produce things. We can’t produce things the same way that people have been producing electronic chip for the electronic industry. We now have to look for ideas, completely different ideas, how to take these rough surfaces and introduce them into a system that looks just like a electronic circuit, other than the fact that this electronic circuit can be bent, stretched, and can survive for as long as we want in a biological environment. The black lines that you see there, these are the very, very rough surfaces that you see on the left. The support is actually made of silicon. It is not silicon; it is exactly the same material that implant