They got some rats addicted to cocaine but not before loading them up with light sensitive proteins called rhodopsins that were placed in their prefrontal cortex, attaching to the neurons there.
By shining a tuned laser light on to the prefrontal cortex, it was possible to activate and deactivate the cells. By turning them on with the laser, the addictive behavior of the rats was removed. Turning them off, even in non-addicted rats, saw the addictive behavior return or introduced.
Now, on to humans...
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