April 9, 2014
Rat Study Shows Memory Storage During Sleep Can Be Manipulated
Brett Smith for redOrbit.com - Your Universe Online
Previous research has shown that the brain strengthens and maintains recently acquired memories during sleep and a new study has found that introducing new memories to a sleeping brain disrupts these natural cognitive processes.
During sleep, the brain shuffles information from short-term to long-term memory. Studies have shown that the "replay" of freshly learned data while asleep plays an essential role in memory. However, it was unknown if presenting new data during slow-wave sleep (SWS) – a stage of deep sleep during which the brain's sensory systems are unreceptive – affects memory.
In the new study, published by the Journal of Neuroscience, researchers trained the animals to affiliate particular odor data with a minor foot shock while they were awake. Once the animals began to predict the shock after detecting the odor, as seen through fearful behavior, the study team released the odor when the animals were in SWS.
The researchers found animals that obtained a replay of the odor during SWS demonstrated elevated memory for the odor compared with animals that received a comparable replay of the odor while awake.
Next, the team subjected their rats to new and previously experienced odors while the animals slept. To exactly control the animals' odor experience during wakefulness and sleep, the scientists provided electrical stimulation to brain circuits included in odor processing as opposed to counting on the delivery of actual odors to the animals.
The researchers found rats that obtained a replay of new odor as they slept exhibited greater problems differentiating the learned odor that they were exposed to earlier from other scents.
"While previous work has demonstrated the role of sleep replay on memory strength, these are the first data to show that memory accuracy can also independently be influenced during sleep," said study author Donald Wilson, from the New York University Langone Medical School.
"We know that during slow-wave sleep, the brain's sensory systems are far less responsive to normal inputs," he added. "Our data suggest this sensory isolation may help allow replay of learned information in the absence of external interference, providing strong, precise memory of important information."
"What we think is happening is that during slow-wave sleep, neurons in the brain communicate with each other, and in doing so, strengthen their connections, permitting storage of specific information,” Wilson added.
Commenting on the new study – Jan Born, a neuroscientist who studies sleep at the University of Tübingen in Germany, said the findings could eventually prove useful in treatment those with traumatic memories.
"The question of whether cueing memories during sleep, and specifically during slow-wave sleep, can be used to modify specific memories is currently a hot topic due to the potential for such information to lead us to new ways to weaken the unwanted memories commonly found in psychiatric conditions such as post-traumatic stress and anxiety disorders," he said.
Treating PTSD has been of particular concern for those returning from the wars in Iraq and Afghanistan. According to the US Department of Veterans Affairs, about 11 to 20 percent of veterans returning from those wars experience PTSD.