In Macbeth Shakespeare wrote that sleep “...knits up the raveled sleep of care.” So why would anyone want to be purposely reminded of a fearful memory while sleeping? Strange as it may seem, recent research shows that reminders of a scary memory while snoozing may help treat phobias.

Scientists showed volunteers two faces while the volunteers received mild electric shocks. As they viewed a face, the subjects also smelled a specific odor, like clove, mint or lemon. So both the face and the odor were associated with the unpleasant experience of being shocked.

Later, when subjects were in deep sleep they were exposed to one of the odors. When they woke up, they viewed images of the two faces. And their fear reaction to the face associated with the smell was lower than when they saw the other face. Fear was quantified via brain scans and sweat measurement. The study is the journal Nature Neuroscience.

It’s known that people can overcome phobias by exposure to the feared object or behavior while awake. This study marks the first time scientists have tried exposure—albeit through a conditioned response—during sleep to reduce fear. For phobic people, it could be a dream come true.

—Christie Nicholson

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]