SACHA PFEIFFER, HOST:
Certain drugs like ketamine and PCP can cause an out-of-body experience. Now scientists think they know why. As NPR's Jon Hamilton reports, they've been able to induce this altered state in a person without drugs.
JON HAMILTON, BYLINE: Psychiatrists call it dissociation. A person feels separated from their own thoughts and body. Dr. Karl Deisseroth of Stanford University wanted to know what causes the phenomenon, so he had his lab study the brain activity in mice given ketamine and other mind-bending drugs.
KARL DEISSEROTH: It was like pointing a telescope at a new part of the sky, and something really unexpected jumped out at us.
HAMILTON: Deisseroth says in one very specific area of the brain, they found a distinctive rhythm.
DEISSEROTH: We saw this patch of the brain oscillating three times a second. The neurons, the cells were firing away three times a second.
HAMILTON: Then using a tool called optogenetics, the team was able to artificially generate this rhythm, and the mice behaved like they were on ketamine. Deisseroth says what's more, brain areas that had been working together were suddenly out of sync.
DEISSEROTH: And so we could see right before our eyes dissociation happening.
HAMILTON: But that was in mice. Deisseroth wanted to know about people, and he got some help thanks to an informal gathering of scientists in his lab.
DEISSEROTH: They were talking about their work. And one of the neurosurgeons said, hey, you know, we have a patient.
HAMILTON: A patient with a form of epilepsy that sometimes causes dissociation. And as part of the treatment, this person had electrodes temporarily implanted in their brain. Deisseroth says that let his team monitor some of the same brain cells they'd been studying in mice.
DEISSEROTH: There was a rhythm that appeared, and it was an oscillation that appeared only when the patient was dissociating.
HAMILTON: To confirm the finding, the team delivered pulses of electricity to the areas where they'd seen the rhythm.
DEISSEROTH: Stimulation in regions that had this oscillation actually caused dissociative symptoms in this patient. So we knew it wasn't just, you know, a coincidence.
HAMILTON: The ability to control dissociation could help a wide range of patients. Dr. Ken Solt, an anesthesiologist at Harvard Medical School, says sometimes you want to prevent an out-of-body experience.
KEN SOLT: In the operating room, we'd love to have a drug like ketamine that just produces the pain-killing properties without having these other psychological manifestations.
HAMILTON: Preventing dissociation might also help patients who have schizophrenia or are recovering from a traumatic experience. But dissociation can also be beneficial. Solt says the drug ketamine appears to help people with severe depression in part because it temporarily desynchronizes areas of the brain.
SOLT: There seems to be this link between dissociation and the antidepressant effect of ketamine because if you don't give enough to at least induce dissociation, it seems like you don't really have an effective antidepressant effect.
HAMILTON: The new research appears in the journal Nature.
Jon Hamilton, NPR News.
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