In a study from Virginia Tech, scientists found out why people with PTSD relive lots of fear memories in sleep.
During periods of rapid eye movement (REM) sleep, brain activity often resembles that of awake behavior.
At times, the brain can actually be more active during REM sleep than when you’re awake. It’s why REM sleep is sometimes called “paradoxical sleep”.
And for those who experience post-traumatic stress disorder (PTSD), this very active sleep stage tends to be fraught with emotionally charged dreams, “over and over”.
In the study, the team explored at a deeper, mechanistic level how the brain may—or may not, with PTSD—effectively process and extinguish fear memories.
The team then probed how the atypical neurotransmitter levels seen in the sleeping PTSD patient’s brain could disrupt the fear-quelling work of those brain rhythms.
With PTSD, neurotransmitter levels stay high during REM sleep. The team’s models show that under these altered conditions, brain rhythms typically effective in healthy individuals can no longer inhibit fear memories.
Instead, the PTSD patient’s brain seems to need higher-frequency rhythms to extinguish fear memories.
Unlocking those higher frequencies could inform therapies to return the restorative quality of sleep to people experiencing PTSD.
The team also found that a specific frequency of brain rhythms was particularly effective at inhibiting fear expression cells.
When inputting frequencies in the theta range of rhythms typical for humans—four to eight hertz—they found that lower-frequency theta rhythms of around four hertz most effectively strengthened connections between frontal areas and the amygdala.
The researchers then modeled REM sleep in people experiencing PTSD. It’s known that PTSD causes norepinephrine levels to remain high during REM sleep.
By pinpointing the atypical frequencies of brain rhythms that can inhibit fear memories in PTSD patients, the team believes they can tap into therapies.
Their next step is to look at ways to trigger adjustments to the sleeping PTSD patient’s brain rhythm frequencies to reach the right rhythms for them.
It’s possible to do so using what Vijayan calls covert auditory stimulation.
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The study was conducted by neuroscientist Sujith Vijayan et al and published in the Journal of Neuroscience.
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