Fragmented Sleep, Missing Memories
For years, sleep researchers have been able to show the relationship between interrupted or fragmented sleep and problems with memory. Until recently, however, no study has been able to narrow down which factor of fragmented sleep was the root cause of this problem. A new study that was recently published in the Proceedings of the National Academy of Sciences may provide the next piece for this part of the sleep puzzle.
When a person’s sleep is interrupted, as it is in those with sleep apnea, it can degrade the overall quality of their sleep, decrease the number of cumulative hours of sleep they get, decrease the amount of cumulative REM sleep they get, and interfere with other specific parts of the sleep cycle. The standard way of studying the effects of sleep interruption, waking participants up to fragment their sleep, has made isolating the various factors impossible. But new research from Stanford University used a unique approach that may help clarify why fragmented sleep leads to issues with memory.
The challenge the research team faced was finding a way to “stir” participant’s brains enough to cause sleep fragmentation without actually awakening them. This would enable them to isolate the effects of interruptions on brain activity without causing degradation in the other areas, allowing them to prove the actual interruption is causing the memory loss rather than lack of sleep or degraded REM sleep.
With mice as their subjects, the team injected a virus that reacts to the flash of a laser diode by stimulating the portions of the brain involved in awakening. This method allowed the team to cause sleep interruptions every 60 seconds without actually waking the mice up. A second group of mice without the virus also experienced the laser diode flashes on the same schedule while they slept. With this method in place, the team could test the theory that fragmented sleep on its own effects memory.
Mice, like most animals, are always more interested in exploring new things than things that are familiar and will behave differently in new surroundings than they do in familiar territory. This made them ideal participants for looking at how sleep interruptions affect memory and retention of new information. The research team introduced both groups of mice to a new cage environment before they went to sleep, allowing them time to explore and become familiar with this new environment. Upon waking, both groups of mice were put back into the same environment so that their behaviors could be observed. As expected, the mice in the control group behaved like they were in familiar surroundings. The story was much different for the mice whose sleep had been interrupted; those mice behaved as if they were in a new cage and explored their surroundings as if it were the first time.
This is a crucial finding as it points to a specific tie between sleep fragmentation and difficulties storing and retrieving new memories. Many researchers in the field of sleep medicine believe that one of the reasons we need to sleep is to consolidate and store our recent memories in our larger long term memory bank, almost like downloading today’s files from your computer to a server. Part of this process is the packaging and transmission of these memories from one part of the brain to another. Using this theory as a foundation, interruptions during sleep could effectively be corrupting or deleting those memory packages while they are in transit, which would explain why interrupted sleep specifically causes problems with memory.
These important findings pave the way for future research that may help those who suffer from chronic sleep interruption due to sleep apnea, alcoholism, or Alzheimer’s disease.
About Valley Sleep Center:
Since 2002, Valley Sleep Center, accredited by the American Academy of Sleep Medicine, has provided Arizona with diagnostic sleep disorder testing in a home-like atmosphere, ensuring a comfortable, relaxing experience for patients. Their Board Certified Sleep Medicine Specialists consist of experienced and knowledgeable physicians who provide expert advice across a multitude of sleep related disorders including insomnia, sleep apnea, snoring, excessive daytime sleepiness, hypertension, sleepwalking, and pediatric sleep problems. They accept most insurance plans as well as Medicare. For more information contact Lauri Leadley at 480-830-3900; http://www.valleysleepcenter.com.
- Fragmented sleep may impair memory, learning (seattletimes.nwsource.com)
- Scientists Use New Technology to Show That Interrupted Sleep Impairs Memory in Mice (neurosciencenews.com)
- Can you pay off your sleep debt? (valleysleepcenter.com)