Those discoveries could lead to new sleep therapies that will improve memory for aging adults and those with dementia, Alzheimer's and schizophrenia.
Earlier research found a correlation between sleep spindles - bursts of brain activity that last for a second or less during a specific stage of sleep - and consolidation of memories that depend on the hippocampus. The hippocampus, part of the cerebral cortex, is important in the consolidation of information from short-term to long-term memory, and spatial navigation. The hippocampus is one of the first regions of the brain damaged by Alzheimer's disease.
UC Riverside psychologist Sara C. Mednick and her research team demonstrated, for the first time, the critical role that sleep spindles play in consolidating memory in the hippocampus, and they showed that pharmaceuticals could significantly improve that process, far more than sleep alone.
"We found that a very common sleep drug could be used to increase verbal memory," said Mednick, who led the study.
"This is the first study to show you can manipulate sleep to improve memory. It suggests sleep drugs could be a powerful tool to tailor sleep to particular memory disorders," he added.
A total of 49 men and women between the ages of 18 and 39 who were normal sleepers were given varying doses of zolpidem (Ambien) or sodium oxybate (Xyrem), and a placebo, allowing several days between doses to allow the pharmaceuticals to leave their bodies. Researchers monitored their sleep, measured sleepiness and mood after napping, and used several tests to evaluate their memory.
The researchers found that zolpidem significantly increased the density of sleep spindles and improved verbal memory consolidation.
"(P)harmacologically enhancing sleep spindles in healthy adults produces exceptional memory performance beyond that seen with sleep alone or sleep with the comparison drug (sodium oxybate)," according to the sleep researchers.
"The results set the stage for targeted treatment of memory impairments as well as the possibility of exceptional memory improvement above that of a normal sleep period," they noted.
Mednick said one of the next steps in this line of research is to determine which component of the physical response to Ambien - the amnesia associated with the drug, or something related to a specific aspect of sleep - is responsible for increasing the density of sleep spindles and the resulting consolidation of memory. She also hopes to study the impact of zolpidem on older adults, who experience poor declarative memory and also decreased sleep spindles. Individuals with Alzheimer's, dementia and schizophrenia also experience decreases in sleep spindles.
The groundbreaking research appeared in a paper published in the Journal of Neuroscience.