A new study shows that sleep spindles, short bursts of brain activity that occur during a sleep phase and are picked up by EEG, may regulate anxiety in people with post-traumatic stress disorder (PTSD).
The study sheds light on the role of spindles in relieving anxiety in PTSD and confirms their established role in transferring new information into long-term memory storage. The findings challenge recent work by other researchers that has indicated that spindles may increase intrusive and violent thoughts in people with PTSD.
The final draft of the preprint is published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging on May 3, 2023.
“These findings may be significant not only for people with PTSD, but also possibly for people with anxiety disorders,” said lead author Anne Richards, MD, MPH, of the UCSF Department of Psychiatry and Behavioral Sciences, the Weill Institute for Neurosciences and the St. Francis VA Medical Center.
“There are non-invasive ways that could harness the benefits of this stage of sleep to alleviate symptoms,” he said.
The researchers enrolled 45 participants who had experienced combat or non-combat trauma; about half had moderate PTSD symptoms and the other half had milder symptoms or were asymptomatic. The researchers studied spindles during non-rapid eye movement 2 (NREM2) sleep, the stage of sleep in which they primarily occur, comprising approximately 50% of total sleep.
Violent images used to test brain processing
In the study, participants attended a “stress visit” in which they were shown images of violent scenes, including accidents, war violence, and human and animal injury or mutilation, before a monitored nap in the lab that took place about two hours later. .
Anxiety surveys were conducted immediately after exposure to the images, as well as after naptime when recall of the images was tested. The researchers also compared anxiety levels at the stress visit to those at a control visit without exposure to these images.
The researchers found that the frequency of spindle speed was higher during the stress visit than during the control visit. “This provides compelling evidence that stress was a contributing factor to spindle-specific sleep rhythm changes,” said first author Nikhilesh Natraj, PhD, of the UCSF Department of Neurology, Weill Institute for Neurosciences and the San Francisco VA Medical Center. In particular, in participants with increased PTSD symptoms, increased spindle frequency after stress exposure reduced post-nap anxiety.
Sleep medications and electrical stimulation may promote sleep spindles
The naps in the study occurred shortly after exposure to violent images, raising the question of whether sleep that occurs days or weeks after the trauma will have the same therapeutic effect. The researchers believe this is likely and point to interventions that could trigger the spindles associated with NREM2 sleep and benefit patients with stress and anxiety disorders.
Prescription drugs such as Ambien are one option that should be studied further, “but a big question is whether drug-induced spindles can also trigger the full set of brain processes associated with natural spindles,” Richards said.
Electrical brain stimulation is another area for further study, the researchers said. “Transcranial electrical stimulation in which small currents are passed through the scalp to drive spindle rhythms or so-called directed memory reactivation, which involves a cue, such as a smell or sound used during an experimental session and reproduced during sleep, it can also induce spindles”. Natraj said.
“Rather than such inventions, sleep hygiene is definitely an easy, zero-cost way to ensure we’re entering sleep phases appropriately, thus maximizing spindle benefit immediately after a stressful episode,” he said. .
The researchers’ next project is to study the role of spindles in the consolidation and reproduction of intrusive and violent memories many weeks after trauma exposure.
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