 of these cells, dendrites coming out. And both of these cells are projecting into the brain. They're pulling part of the optic nerve project to the brain. And so, he recorded from these two cells in their fire room. Now, this mouse at this time has over 100,000 of these cells. What are we recording from these two? What about all the other ones? So, to get a picture of what the other ones do, we do, instead of recording from cells, we do an imaging of the cells of the entire retina, or a good chunk of the retina, to see what happens. And what you find is something quite amazing. And I think it's a movie. Maybe it won't work, but let's see. Let me just try this again. But what I was about to show... Excuse me? You want to try it? Maybe you should come out of power trinus. I don't know. Maybe it's nothing, but it's actually quite an amazing thing. So, what you see is this. If you're imaging the entire retina, what you see is, what I just showed is called an activity. But what you see is a wave of activity, like a wave, it's called a retina wave, sweeps across the retina, in one direction. What the heck was that? Now you wait for... Can you go backwards? Yeah. Do you have a question? Yes, go ahead. There's no relation between the frequency of the spikes with the temperature or background radioactivity, for instance? I'm sorry. It's temperature and what? Background radioactivity. Background radioactivity. I don't know about radioactivity, because we try to avoid radioactivity. So we don't look at radioactivity. With temperature, yes. Okay, so now let me just get to this. So here's an area of the retina. It's about two by two. And what you'll see is, this works, is a cloud going across this. So it's just background activity. See that cloud? That's thousands of cells firing. Keep your eye on that. Now, this is five times real time. You're looking at this thing, nothing, nothing, nothing. Five times real time, speed it up. Now watch this in a second. See that? You see that dark thing going across that way, that dark cloud? That's thousands and thousands of cells firing the action potentials. This is imaging with a calcium imaging dye. Now, see that little? It's random across the retina. These waves spread. See that? Do you see that? It's an amazing thing because about every five minutes it happens, so it varies, okay? This is just background activity, nothing, nothing, nothing. There's no light here, you know? See, there's no light, there's no photoreceptors. There's another one like that. And these waves occur during a specific period of development when connections are being formed in the brain. So now I'm going to get to your question. Radiativity, I don't know, because there's no reason why we test that. But with temperature, yes. So what happens is these are done in body temperature, in normal body temperature. If you lower the temperature, the waves become much slower, much slower in frequency. But a lot is known about these waves. They must be a thousand. They must be now a thousand. They must have written about them. And we've looked at these in mouse and ferret and fetal monkey. That happened when you were in utero when I was in utero. They just spontaneously stopped like that. So my first point is do no harm, because if you do harm, you can impact a number of things, not the least of which is intellectual activity. That's important for refining connections to the brain. And then the connections are not what they normally should be. So the baby is born at a disadvantage. The second thing that is absolutely certain from the data we have, including the work of two prize winners in my field, which I'll tell you about in a minute, is, and this has had a major impact on how children are treated in American hospitals, and I assume here as well, shortly after birth, correct sensory impairments at an early possible time. So here is about 3% of the babies in the world are born with this condition. It's called ambiopia. You see this eye? It's deviated, like so. That's a pretty serious deviation. Sometimes it's slight, which is hard to catch. Here's what happens. That eye will not be properly stimulated during the early development. And then when a child goes to school and they can't read well, they try to correct that, they find they cannot correct it with anything. And the reason is this, that because this eye is not getting proper activity during development, the connections of this eye to the brain are completely disconnected. Completely disconnected. Not just functional, and atomically they shrink to about 1-100 of what they should be depending on how severe this is. This was fired to discover working on cats and monkeys by David Hubel and Thorsten Wiesel who were not by price, but his work at Harvard Medical School. Hubel died about a year and a half ago and Thorsten Wiesel is still alive. He's in his late 80s now. And so as a result, now when a child is carefully examined and has any kind of deviation that they corrected as soon as possible, because if you wait, it's too late. That brain is functionally and structurally disconnected from the visual centers of the brain. Nothing you can do. And as a result, a lot of effort has been made into testing children for vision. So here's one. A woman called DeVita Teller at the University of Washington, Seattle developed this very simple. You know, we talked about computers, high tech, this and that. You know, everybody's into that. They're saying that simple costs $5 to make. It's been cited thousands of times in literature. So here's what Dr. Teller did. She wanted to test what the kids see when they're first born. They don't see the way you and I see it. So she gets a mother. That's the mom. That's the baby. She has the baby look at this. And here's what the baby sees. That's the baby looking. Either stripes like this on one side, here's where the baby's first pointing on this thing, or nothing. What happens? Babies like people like to look at something as opposed to nothing. So when this comes on, sometimes comes on here, sometimes comes on here, the baby's eyes, looks through the stripes, okay? Because there's nothing to look at here. And so what she does and what she actually does is changes the frequency of these stripes, more stripes, higher spatial frequency, and thereby determining the purity of the baby, okay? At some point, the frequency of these stripes is such that the baby can't tell the difference between this and this. In which case it's looking as random. So they're able to do exactly what optometrists does, because spatial frequency is a bit. So you and I, under optimal conditions, if your vision is perfectly corrected, can see 40 stripes per visual angle, 40. Light, dark, light, dark, light, dark, like that. A baby can see much less and so here's the kind of thing she was able to get. So this is the spatial frequency vision of babies. From one of age, they can barely see the purity of the green, barely half a cycle per degree. So what that means is when they're looking at you, they just see, like a blur, a blur. Eyes like that. And rapidly, look, first year, spatial purity gets better and better and better and better and better like that. Up to four years of age when it's really kind of reaches almost adult limit. So the first four years of life, the spatial purity of the baby is improving, improving, improving. And with this kind of graph, a mother can take her baby to the clinic and say, where does that baby fall in this thing? Here or here or where? So you notice a normal, a normal, how do we fix it? By the way, these studies have also, an visual system, have also been used. So every baby born in a teaching hospital in the United States is immediately tested for hearing. And they provide different earphones, they provide different frequencies and they look at that and they can immediately tell you 10 minutes, usually 8 minutes if the baby has normal hearing or not. If the baby doesn't have normal hearing, they do what I told you. Fix it as soon as you can. They implant electrodes into the cochlea. That baby's hearing will be perfect. Language will be perfect. They get it very early. So about 1% of the babies in America are born with impaired hearing. Those babies would have poor language and would have hearing problems and not being totally deaf for life. They can now do that. Not just can you hear or not, but do you have a hearing impairment by giving different frequencies and recording brain waves? So that all came out of these studies on the visual system by Hubel and Liesl. Now this is something, before these studies were done, a picture from the New York Times many, many years ago, before these studies were done so that we knew that activity in the two eyes was absolutely essential to have the normal connections. So this is a picture that they had of a boy, this little boy who fell and bruised his eye all around here. So they patched the eye. So now he doesn't get normal activity through his eye. They're actually making this eye disconnected from the brain by patching his eye. And by the way, two or three days is enough to make a change during a certain period of time. So he patched his eye. So this kid, of course, doesn't like it. So what he does is, he rips the patch off. So what they do is, they put these arm guards on him. So not only are they disconnecting his eye from his brain, the probation has arms as well. And this is like a cute picture saying, oh, look how Tommy tries to smart the doctors, but the doctors are smarter than him. So they put this thing in his hand so he couldn't rip the thing off. They never do that anymore for the reasons that I just showed you. So the third thing is, and this is something most parents know, is optimal periods for learning do exist and should be taken into account in design learning programs. So there are these people, critical periods. The idea of critical periods actually came from work done by animal behaviorist Conrad Lorenz in Germany. And this is him. He won another prize for this. And what he found by accident really is that if you have ducklings follow you a certain part after hatching, they treat you like the mother and they follow you everywhere. They ignore other types of ducks. And it's just a certain period of time. And so here he is with these ducks going out. Now they're adults.