What causes obsessive-compulsive disorder or OCD? How can it be stopped? These two questions have propelled two separate teams of researchers to study OCD in mice using a new technology called optogenetics. The light-activated technology stimulated neural circuits in mice, allowing the researchers to both turn on and off obsessive behaviors.
The two studies, conducted separately, were both published June 7 in the journal Science.
The first study was led by Susanne Ahmari, assistant professor of clinical psychology at Columbia University. Ahmari and her team used optogenetics to stimulate a particular region of mice brains using bursts of light. Just stimulating the brain a single time didn't have an effect, but stimulating the brain for five minutes a day for several days in a row created OCD-like behavior. "We saw a progressive development of repetitive behaviors — in this case, repetitive grooming behavior — that persisted up to two weeks after the stimulation was stopped," Ahmari said in a press release. Her team then treated the mice with fluoxetine, a commonly used OCD medication, and their repetitive grooming ceased.
Ahmari discusses her research in this video from Columbia University Medical Center:
The second study was conducted by researchers at Massachusetts Institute of Technology. This study used similar optogenetics techniques but created an opposite reaction from the Columbia study: they blocked obsessive behaviors. "You don't have to stimulate all the time," said senior author Ann Graybiel. "You can do it in a very nuanced way."
In this case, the mice tested carried a mutant gene called Sapap3 that is linked to both addiction and repetitive behavior. The mice were specifically trained to groom at certain times after water was dripped onto their foreheads. The researchers then stopped dripping water on the mice, but they continued their grooming behavior. After they stimulated the mice's neurons with light, the grooming behavior ceased.
Both teams say their research could have future benefits for humans with OCD, Tourette's syndrome and similar conditions.
Optogenetics was invented at MIT, which produced this video in 2011 to explain the technology:
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