When you sleep your brain goes through five distinct phases which repeat over the course of the night. The phase that’s the star of the show is rapid eye movement (REM) sleep: This is when your brain and body become energized and, importantly, when you dream. REM sleep is known to help store memories, balance your mood, and, according to new research, help individuals be less fearful of the scary things around them.

In a paper released Monday in The Journal of Neuroscience scientists from the Center for Molecular and Behavioral Neuroscience at Rutgers University explain that their study is the first to demonstrate that how well humans are sleeping prior to being exposed to a fear stimuli, affects how strongly they react to that stimuli. Previous research has found that individuals with PTSD often have poor REM sleep: This study suggests that high-quality REM sleep prior to trauma could subsequently help individuals cope with their fear memories.

“Ultimately, our results may suggest that baseline REM sleep could serve as a noninvasive biomarker for resilience, or susceptibility, to trauma,” the researchers write. “Current studies of sleep in individuals with PTSD have shown REM abnormalities such as low levels of REM and REM fragmentation.”

More time in Rapid-Eye-Movement sleep predicted less connectivity between key brain regions that are involved in fear learning.

The scientists claim this study demonstrates that higher baseline levels of REM sleep predicted “reduced fear-related activity in, and connectivity between, the hippocampus, amygdala, and ventromedial PFC during conditioning.”

To establish this, the scientists recruited Rutgers University students to monitor their sleep at home for a week with a headband that measures brain waves and a bracelet that measures arm movements. They were also asked to keep a sleep log noting the times that they fell asleep and when they woke up. This part of the study is what allowed the scientists to see what sort of quality REM sleep they were receiving: In the second part of the study, the students came to the lap to participate in a neuroimaging experiment where they learned to associate a neutral image (pictures of three differently colored lamps), with an electric shock that was considered “highly annoying but not painful.”

Analysis revealed that the students who spent more time in REM sleep demonstrated weaker modulation of activity in their brain during the fear learning experiment. This result supports previous animal model research that found REM sleep reduces levels of norepinephrine in the brain, a substance that is predominantly released from the ends of sympathetic nerve fibers that prompts the body’s flight-or-flight response. The Rutgers scientists believe that lower levels of norepinephrine helps individuals be less sensitive to fearful stimuli.

While getting more REM sleep to cope with fear may be a simple piece of advice, it’s also an effective one. Sleep contributes to both the development and persistence of fearful memories, which create real-life effects when you’re awake.


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