Alan McStravick for redOrbit.com – Your Universe Online
Once asleep, we all experience five different stages in our sleep cycle. That being said, one would be hard pressed to find anyone who is familiar with any of the cycles besides REM sleep, or rapid eye movement sleep, which is typically characterized by quick and random movements of the eyes combined with muscle paralysis.
During REM, neural activity in the brain intensifies showing a similarity to the activity associated with being awake. This is the stage where most people experience vivid dream activity.
In a recent study conducted by the University of California´s Riverside and San Diego campuses, researchers were able to delve further into the known sleep mechanisms to identify how the brain consolidates emotional memory. Additionally, they were able to determine how a popular prescription sleep medication can adversely play a role in the recollection of and response to negative memories.
The team´s study, entitled ℠Pharmacologically Increasing Sleep Spindles Enhances Recognition for Negative and High-arousal Memories´ could advance study aimed at individuals who suffer long-term insomnia as a result of posttraumatic stress disorder (PTSD). Often, these individuals are prescribed the prescription medication Ambien to help them sleep.
Sara C. Mednick, assistant professor of psychology at UC Riverside, along with UC San Diego psychologists Erik. J. Kaestner and John T. Wixted, was able to determine how sleep spindles are important for emotional memory. Sleep spindles are characterized by short bursts of brain activity that last a second or less during a specific stage of sleep.
Previous research published by Mednick had clearly shown how sleep spindles played a critical role in helping to transition information from short-term to long-term memory in the hippocampus. That research, presenting potential benefits for sufferers of Alzheimer´s disease and other age related dementias, showed how Ambien might be an effective method of manipulating the brain for improved memory through pharmacology.
“We know that sleep spindles are involved in declarative memory – explicit information we recall about the world, such as places, people and events,” Mednick explained.
This current study, published in the Journal of Cognitive Neuroscience, is the first study of its kind to consider how sleep spindles play an integral part in emotional memory. All previous research had looked only at REM.
By utilizing two of the more commonly prescribed sleep aids — Ambien and Xyrem — the team was able to separate the effects of sleep spindles and REM sleep on the recall of emotional memories. Their study showed REM had no discernible effect on emotional memory, as previously thought.
In the conduct of their study, the team distributed Ambien, Xyrem and a placebo to their study group comprised of 28 men and women aged 18 to 39. Each person in the study was considered a normal sleeper. The team presented a series of images to the participants for one second both before and after a supervised nap. Each of the participants was able to recall more of the images that had negative or highly arousing content after having taken Ambien. The team contends this may suggest the brain favors consolidation of negative memories.
“I was surprised by the specificity of the results, that the emotional memory improvement was specifically for the negative and high-arousal memories, and the ramifications of these results for people with anxiety disorders and PTSD,” Mednick said. “These are people who already have heightened memory for negative and high-arousal memories. Sleep drugs might be improving their memories for things they don´t want to remember.”
Despite the US Department of Veterans Affairs and the Department of Defense recommending against the use of benzodiazepines for the treatment of PTSD, use has increased among both men and women with PTSD between 2003 and 2010. Benzodiazepines have a similar effect on sleep to Ambien.
Also noted in the study is that for crews who have finished a long mission where the use of stimulants was required, the US Air Force uses Ambien as a prescribed “no-go pill” to aid the crew in calming down.
“In light of the present results, it would be worthwhile to investigate whether the administration of benzodiazepine-like drugs may be increasing the retention of highly arousing and negative memories, which would have a countertherapeutic effect,” they wrote. “Further research on the relationship between hypnotics and emotional mood disorders would seem to be in order.”