We began our journey into the human brain here on the campus of Dartmouth College in New Hampshire. I'd come to meet one of the world's leading brain scientists, Mike Gazzaniga, and a man he's worked with for over a decade. A man with two brains.
You've been working a long time with Dr. Gazzaniga? 14 or 15 years. It doesn't seem like that long, does it? The collaboration began when Joe had surgery. And you had this procedure to correct an epileptic problem, is that right?
Yes, to try to stop the seizures. I was having seizures like every day or so, or sometimes two or three a day. To control Joe's epileptic seizures, a surgeon severed the connection between the two halves of his brain. Cutting the corpus callosum like this prevented the spread of the electric storms that caused his seizures.
But it also prevented the left and right halves of his brain from communicating with each other. In the years since the operation, Joe's epilepsy has been under control. He now earns a living at an egg farm.
And in his everyday life, he's largely unaffected by the fact that his left and his right brains work independently. Do you feel any difference? different when you think about something than you did any differently from the way you felt before the procedure? It's just better back up brain, that's all.
That's something everybody could use. I found out how true that was right away when I was asked to drive. draw a different shape with each hand.
In a brain like mine, roughly speaking normal, at least all in one piece, the left half of my brain controls the right side of my body, while the right brain controls the left side. Oh no. But because the two halves are connected, nothing wrong with that, getting each hand to work independently isn't easy. Well, we're seeing the fact that Alan's hemispheres are connected.
And that the motor messages from one are confusing the motor messages in the other. I was just drawing an upside-down duck. But when Joe is given the same task, his two hands operate as if controlled by two separate brains. What's happening is that each half of Joe's brain is given a separate instruction.
He's asked to fix his eyes on the cross in the center of the screen. Anything flashed to the right of the cross goes only to his left hemisphere. Things to the left of the cross go to his left hemisphere. go to his right hemisphere.
Because the two don't communicate, each hand does only what its half of the brain sees. Wow, look at that. It's really like two different people doing the same task. That's right. That's the idea.
Okay, Joe, I want you to keep your hands up. In an experiment that's now a classic in brain research, Mike Kazaniga, over 30 years ago, used a similar setup to find out if the two halves of the brain are specialized to do different things. Joe is being flashed a word only to one half of his brain. Words flashed to the right are seen only by his left brain, and Joe can report seeing those words just fine. Good.
But when a word is flashed to his right brain, I didn't see that. Okay. So I'm going to ask you to draw that with your left hand.
You're going to be lost. Why don't you try drawing another picture of the driver here? That will help you.
All phone. Oh, okay. Der.
It's almost as though somebody has given him a secret communication. That's right. And now he knows that it's a telephone.
Up until then, he was blind to it. Exactly. When Gazzaniga first did this experiment, it instantly... proved that the ability to speak resides almost exclusively in the left hemisphere.
Not until he sees what his right brain is drawing is Joe able to name it. He said church town after looking at the picture. But he had it figured out about as long as we did.
It's really interesting. It's a picture here of somebody communicating almost with another person. The communication is not occurring inside the head. It's occurring out on the piece of paper.
Blob. I don't know. You want to draw a little bit more?
So far, Joe has been seeing only one word. Things get even stranger when he's flashed two words, each to only one half of his brain. The right hemisphere saw a toad. Yeah. And so his left hand draws a toad.
So there's the toad. Oh, it's a toad. And this time I was able to guess what was coming. We'll put a little three-legged stool in there later? Joe's speaking left brain saw stool.
Saying the word lets the hand that's controlled by his right brain in on the cigarette. That's great. That's really interesting. And if he had seen that with the corpus callosum intact, he would have drawn a toadstool. Right.
Not a toad and a stool. Right, exactly the point. I've been doing this for 35 years. Yeah?
And it gets me every time. Yeah, it must.