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Scientists say they have induced imaginary sounds in the brains of both people and mice. That discovery could lead to better drugs to treat schizophrenia and other brain disorders that cause hallucinations. NPR's Jon Hamilton has the story.
JON HAMILTON, BYLINE: A mouse can't tell you when it's hallucinating, so researchers haven't had much luck using rodents to test drugs meant to prevent hallucinations. Adam Kepecs of Washington University School of Medicine in St. Louis was part of a team that set out to change that.
ADAM KEPECS: So the challenge that we address is how we can find a way to study psychotic disorders in animals.
HAMILTON: Disorders like schizophrenia. The team knew that even healthy brains sometimes perceive things that aren't real, so they found a way to induce false perceptions in both people and mice.
KEPECS: We set up basically a computer game, an audio game by which we could actually measure hallucination-like events.
HAMILTON: Players, whether rodent or human, had to pick out a certain sound from a whole lot of background noise. Kepecs says in this environment, the brain starts to anticipate hearing the sound. That's helpful, he says, if you are, say, trying to listen for your name in a noisy restaurant.
KEPECS: You can imagine, though, that if you're using a little bit too much of your expectations, suddenly your perceptions can be truly divorced from reality.
HAMILTON: And in the experiment, they were. Both mice and people began to respond to imaginary sounds. And Kepecs says the likelihood that they would respond was closely tied to levels of a substance in the brain called dopamine.
KEPECS: What we believe is happening is that baseline dopamine levels are setting the balance between the current sensory evidence that's coming in, the sounds, and our prior expectations of it.
HAMILTON: Too much dopamine and your brain starts hearing things that aren't there. That makes sense because there's a well-established link between dopamine levels and hallucinations, including those caused by schizophrenia. And drugs for schizophrenia are thought to work by blocking the effects of dopamine. But Eleanor Simpson of the New York State Psychiatric Institute says there's been no way to study precisely how dopamine works in the brain.
ELEANOR SIMPSON: Which is why this study is valuable - because it will allow us to use mice and dig into the cellular, molecular, physiological details.
HAMILTON: Simpson says until now, the lack of a good mouse model of schizophrenia has been one reason there aren't better drugs for the disorder.
SIMPSON: We have drugs that treat hallucinations, but they're not very good. They don't work for everybody. And they have a lot of terrible side effects which prevent people from using them.
HAMILTON: Simpson says a better mouse model could make it much easier to test potential new drugs.
SIMPSON: And then when you've made discoveries there, you go back to the patients and you ask, how relevant is this? How does this relate to the patient disease experience and symptoms?
HAMILTON: In other words, does the drug make hallucinations go away? The study appears in the journal Science.
Jon Hamilton, NPR News.
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