Silencing the Siren of the Brain

red ambulance siren graphicIf today was a terrible, horrible, no good, very bad day, chances are things will feel better in the morning.

That’s what a good night’s sleep can do for you, according to researchers at the Netherlands Institute for Neuroscience in Amsterdam who published the results in the July 11 issue of Current Biology.

When something is scary or goes terribly wrong, the amygdala in the brain is activated and sounds the alarm for the body and the brain to pay attention. “In order for the brain to function properly, the siren must be switched off again,” said a news release from the institute. “For this, a restful REM sleep, the part of sleep with the most vivid dreams, turns out to be essential.”

Researchers placed participants in an MRI scanner and upset them (the news release didn’t specify how they did so). At the same time, they exposed the participants to a specific odor.

That night, while in the sleep lab, participants were again exposed to the same odor. The next morning, the researchers tried to upset the participants again in the same way but were unable to do so. Restful REM sleep had done its work.

However, for those who had restless REM sleep, the next morning was no better, the release said. Exposure to the odor during sleep only made things worse.

“Among all remnants of the day, a specific memory trace can be activated by presenting the same odor as the one that was present while awake,” said Rick Wassing, lead author of the study. “Meanwhile, memory traces are adjusted during sleep; some connections between brain cells are strengthened, others are weakened. Restless REM sleep disturbs these nocturnal adjustments, which are essential for recovery and adaptation to distress.”

These findings could have implications for people with mental disorders, such as post-traumatic stress disorder, anxiety and depression, the release said. Restless REM sleep and a hyperactive amygdala are hallmarks of these conditions. The study authors predict the treatment of restless REM sleep could help people process emotional memories and quiet the amygdala.