BOB HIRSHON (host):Putting dreams to rest…I’m Bob Hirshon and this is Science Update.When you start dreaming at night, your body goes into what’s called REM sleep paralysis. This is how your brain keeps your body from enacting your dreams. But according to University of Toronto behavioral neuroscientist John Peever, a small percentage of people don’t always stop moving while they dream.

JOHN PEEVER (University of Toronto):

Dream enactment leads to unwanted side effects such as punching a bed partner, throwing yourself out of bed, even broken bones.

HIRSHON:

Peever and his colleagues have discovered that two brain chemicals, GABA and glycine, tell our brains to freeze our muscles while we dream.

PEEVER:

And what we found was that GABA and glycine act to shut off motor neurons, and this is what triggers REM sleep paralysis.

HIRSHON:

He says the disorder can be a risk factor for Parkinson’s and other neurodegenerative diseases. But he adds that a little bit of movement during sleep is normal. I’m Bob Hirshon, for AAAS, the science society.