JUANA SUMMERS, HOST:
Certain drugs can produce an out-of-body experience, so can a pulse of electricity if it's sent to the right place in the brain. NPR's Jon Hamilton reports on a brain area that seems to keep us attached to our physical selves - well, most of the time.
JON HAMILTON, BYLINE: A few years ago, Dr. Josef Parvizi got a visit from a patient with epilepsy. The man told Parvizi about some very strange symptoms.
JOSEF PARVIZI: My sense of self is changing, almost like I am a third observer to conversations that are happening in my mind that I'm not part of. Plus, they just feel like I'm floating in space.
HAMILTON: Parvizi, a neurology professor at Stanford, was intrigued. He figured the man's seizures must be affecting an area of the brain called the PMC.
PARVIZI: It's hidden in-between the two hemispheres in the back.
HAMILTON: The PMC helps create what's known as our narrative self, a sort of internal autobiography that helps us define who we are. So Parvizi figured the PMC was also responsible for our physical self, which tells us that our body and thoughts belong to us, not someone else.
PARVIZI: As you are sitting in your chair, you have an understanding that it is you looking at me, your point of view in space and in your environment.
HAMILTON: That sense of being anchored in your body disappears when you have an out-of-body experience, like the man with epilepsy. Parvizi and a team were able to recreate the man's symptoms by electrically stimulating the PMC. Then they tried the approach on other volunteers. And Parvizi says it became clear that a person's physical self was tied to one particular spot in that special part of the brain.
PARVIZI: What we discovered is that towards the front, there is this sausage-looking piece of brain called the anterior precuneus.
HAMILTON: Parvizi's team stimulated the area in eight patients.
PARVIZI: And, lo and behold, everybody has changes in their sense of what we call the physical self.
HAMILTON: The results appear in the journal Neuron, and Parvizi says they suggest that the anterior precuneus is critical to understanding that something is happening to me, not another person.
CHRISTOPHE LOPEZ: We think this could be a way for the brain to tag every experience in the environment as mine.
HAMILTON: Christophe Lopez says that makes sense. He's a researcher at the National Center for Scientific Research in France. Lopez thinks that our physical self comes in part from the inner ear, which senses motion and the body's position in space. And he says Parvizi's team found evidence supporting that view. Lopez says the anterior precuneus appears to act as a hub for signals coming from the inner ear.
LOPEZ: When they stimulate these anterior precuneus, you can evoke that the body or the self is floating in the room, like the body is rising or the body is falling like freefall.
HAMILTON: As a result, the inner ear may be saying the body is moving while the eyes say it is stationary. Lopez says that's confusing for the brain.
LOPEZ: Sometimes the best solution, which is found by the brain, is to think that you're somewhere else out of the body.
HAMILTON: It's not just electrical stimulation that can confuse the brain, so can the mind-bending anesthetic ketamine. Patrick Purdon, a researcher at Harvard, has been studying the drug's effects on the brain. He says it acts a lot like brain stimulation when it comes to the anterior precuneus.
PATRICK PURDON: Ketamine seemingly is producing this kind of artificial rhythm that is disrupting function of that area.
HAMILTON: Purdon says that means it might be possible to use electrical pulses in place of anesthetic drugs like ketamine.
PURDON: You could get the specific brain areas that you want without having to cause a brain wide and system-wide effect that might carry with it a lot of side effects.
HAMILTON: Purdon says stimulating the precuneus might even reproduce ketamine's powerful antidepressant effect, though that's never been tried. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.
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