Nothing teaches us how the brain works like neurosurgery, maintains Theodore Schwartz, MD, of Weill Cornell Medicine in New York City.
"We tend to think about neuroscientists, neurologists, and philosophers as the people who try to figure out the relationship between the brain and the mind -- how the brain creates the mind, and how the brain stores memories," observed Schwartz, neurosurgeon and author of a called Gray Matters: A Biography of Brain Surgery.
"But the experiments that neurosurgeons can do -- because they have access to the human brain in a way that no other specialty does -- have given us the ability to contribute to that conversation in a much more meaningful and deep way than most people understand," he said.
In Gray Matters, Schwartz immerses readers in the story of brain surgery, from its primitive roots to the meticulous procedures that now treat epilepsy, cancer, Parkinson's disease, and more. He draws on personal experience as a surgeon and dissects archives and historical records to explain famous cases from JFK to Muhammad Ali.
MedPage Today spoke with Schwartz about what we've learned from the field of neurosurgery and where it might be headed. An edited version of that discussion follows.
In your book, you talk about the "Jennifer Aniston neuron" and what that experiment taught us about memory.
Schwartz: The Jennifer Aniston neuron comes from a study done by a neurosurgeon named Itzhak Fried, who was putting electrodes into the brain to treat epilepsy. He was able to record single neurons firing in and around the hippocampus.
He found there were neurons that would fire only with certain ideas or concepts or people. Any time someone said the name "Jennifer Aniston," or when the patient looked at a picture of Jennifer Aniston or said the name "Jennifer Aniston," one neuron would fire and other neurons would not.
We don't really know how memories are stored in the brain, whether there's just a big network that stores different aspects of someone's face. Maybe there's a nose neuron somewhere that fires when a particular type of nose is seen, and something else for eyes, and something else for ears, and something else for mouth, and something else for skin color. Those are all firing in the same frequency. We bind them together and we have that person's identity. That's a possibility.
Or there's one neuron that literally is like a light bulb. If that neuron doesn't go off, then we haven't recognized that person as somebody that we know.
It raises the possibility that if we were to remove those neurons from the brain, we could have someone who no longer recognizes a person. It's a fascinating idea about how the brain stores memories that wasn't really understood -- or appreciated or accepted -- until this neurosurgeon did that experiment.
What are some intriguing things we've learned from neurosurgery?
Schwartz: One of my favorite groups of experiments has to do with consciousness. We live under the illusion that we're in control of our behaviors and that we have an identity, an "I," a self, that decides what we're going to do and then carries out that task.
If I want to walk across the room and sit on the couch, something inside of me decides to walk across the room and sit on the couch. I think I'm making that happen on my own, that Ted Schwartz is doing that.
But if you put electrodes in the brain and you record parts of the brain that are important for movement, you will find that those neurons become active roughly one second before you have made the decision to do the activity. The brain is already making those decisions for you, well before you're aware of what you're going to do.
It may be that the way the brain works is that there are modules in the brain that control our behavior, and they create those behaviors. Then there are other modules in the brain that see what we're doing and react to it, and fool us into thinking that we made the decision -- that some "I," some illusory self, had agency and made that decision.
A lot of that philosophical way of thinking has come from neurosurgical operations -- either from electrodes in the brain recording activity before someone knows what they're going to do, or from split brain experiments, which are experiments done on patients who had their brain split in half by neurosurgeons treating epilepsy, doing a surgery called a corpus callosotomy.
What have split brain studies revealed?
Schwartz: If you split the two sides of the brain in half, left and right brain, you now have an individual who literally has two separate brains working. But that person does not feel like two people. They don't feel like a divided self. They feel like a unified self, which is puzzling in and of itself -- to think that you can split your brain in half and still feel like one person.
It's possible for researchers then to insert information or feelings into one hemisphere. If it's not the language-controlled hemisphere, you will not be aware; you'll be unconscious that the information has gone into your brain.
Half of your brain, usually the right side, can control your left arm, which can start behaving in particular ways as a reaction to information that's put into the brain. When you ask "why did you do that with your left hand?" a person will make up a story as to why they did it that's consistent with who they think they are, not realizing their behavior was triggered by information unconsciously put into their brain.
This gives us the notion that there may be an enormous amount of processing that goes on below the level of consciousness that's influencing our behaviors and creating behaviors, and we're not aware of it. When we see those behaviors, we then make up a story to pretend that we did it on purpose.
Brain surgery has come a long way in the last 120 years. Where is it headed?
Schwartz: I really think we are at the cusp of a real revolution, whether it's more sophisticated deep-brain stimulation or full-on implantations of wires and chips into the brain to interface it with computers.
That technology is just going to blossom because there are so many companies that are working on it. We now have the ability to take information out of the brain and very quickly and easily translate it into computer commands.
Once you can put something into a computer command, then the sky's the limit because so much of our world now is controlled by computers and accessed by computers. And once we can do that directly with our brain, there are so many possible uses for it, many of which haven't even been imagined.