A recent study by Virginia Tech neuroscientist Sujith Vijayan and his team looked at how the sleeping brain processes emotionally charged memories, specifically in those with post-traumatic stress disorder (PTSD). During periods of rapid eye movement (REM) sleep, the brain is often more active than when we’re awake. In a healthy brain, REM sleep helps process and remove the emotional charged memories. But in PTSD patients, the brain can’t seem to shake the emotionally charged dreams, reliving them night after night.
To figure out what’s going on, Vijayan and his team created models of the sleeping brain to explore why this might be happening. They found that neurotransmitter levels play a big role in the brain’s ability to process and extinguish fear memories during REM sleep. In a healthy brain, levels of norepinephrine and serotonin go down during REM sleep, allowing the brain to inhibit fear expression cells. But in PTSD patients, these neurotransmitter levels stay high, and the typical brain rhythms can no longer inhibit fear memories. The team found that higher-frequency brain rhythms are needed to extinguish fear memories in PTSD patients.
Vijayan describes REM sleep as a kind of “Wild West” in terms of what we know about its relationship with memory. Most of the work in neuroscience focuses on non-REM sleep, and there are still many questions about how REM sleep affects emotional memory processing. Vijayan sought to change that by creating biophysically based models of REM sleep, enabling his team to learn more about what allows brain rhythms to help with emotional memory processing — and how PTSD disrupts it. The models allowed the scientists to manipulate the REM sleep conditions that they believed could be key to this question: neurotransmitter levels.
They found that a specific frequency of brain rhythms is particularly effective at inhibiting fear expression cells in a healthy brain. But in a PTSD brain, these typical frequencies no longer work. The team found that at a higher frequency of 10 hertz, brain rhythms could effectively inhibit fear expression cells in their PTSD model of the sleeping brain. This discovery could lead to therapies that trigger adjustments to the sleeping PTSD patient’s brain rhythm frequencies to reach the right rhythms for them, using what Vijayan calls covert auditory stimulation. The idea is to use desired neural dynamics to engage the recuperative powers of sleep, not only in PTSD, but in other disorders where sleep is disrupted, such as traumatic brain injury or Parkinson’s disease.
Image Credits
In-Article Image Credits
Military Marine soldier suffering PTSD covering face with hands via Wikimedia Commons by US Marines - Battling PTSD with usage type - Public Domain. May 24, 2010Featured Image Credit
Military Marine soldier suffering PTSD covering face with hands via Wikimedia Commons by US Marines - Battling PTSD with usage type - Public Domain. May 24, 2010
