And they will study whether it is involving in controlling sleep quantity alone, or also what scientists call the "wakefulness-behavioral drive."

VOA: special.2009.08.26

The tension of stress can interfere with sleep or cause anger or sadness.

VOA: special.2009.03.24

Then the old man and woman held the rain babies in the palms of their hands or they rocked them to sleep in a pair of wooden shoes.

VOA: special.2009.02.28

Using a combination of technology and pharmacology, he exploits a technique that brings Cobb and his team into a client's or victim's sleep to search out personal or business secrets.

VOA: standard.2010.07.16