January 28, 2013
Memory Loss In Seniors Could Be Due To Lack Of Slow-Wave Sleep
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redOrbit Staff & Wire Reports - Your Universe OnlineA lack of quality, deep sleep could play a vital role in the memory loss sometimes experienced by older men and women, scientists at the University of California, Berkeley have discovered.
Matthew Walker, an associate professor of psychology and neuroscience at UC Berkeley, and colleagues discovered that the brain waves generated during slow-wave sleep help move memories from the short-term storage area that is the hippocampus to a more permanent home in the prefrontal cortex.
However, in older adults, the poor quality and lack of this more restorative type of slumber could mean that the memories aren´t making the transfer. As a result, those memories are forced to remain in the hippocampus, and are ultimately deleted in favor of new short-term memories, the university explained Sunday in a statement.
"What we have discovered is a dysfunctional pathway that helps explain the relationship between brain deterioration, sleep disruption and memory loss as we get older — and with that, a potentially new treatment avenue," said Walker, who is the senior author of a paper detailing his team´s findings. That study was published in the January 27 edition of the journal Nature Neuroscience.
"When we are young, we have deep sleep that helps the brain store and retain new facts and information. But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night,” he added. These findings, the university claims, could help explain some of the forgetfulness that tends to plague men and women as they begin to advance in years.
Typically, adults without sleeping disorders spend roughly 25-percent of their nights engaged in slow-wave, non-REM sleep, the researchers said. The slow waves experienced during this type of slumber are generated from the middle frontal lobe of the brain, and it is the deterioration of this region that the study has linked to the inability of the elderly to generate this type of deep sleep.
“The discovery that slow waves in the frontal brain help strengthen memories paves the way for therapeutic treatments for memory loss in the elderly, such as transcranial direct current stimulation or pharmaceutical remedies. For example, in an earlier study, neuroscientists in Germany successfully used electrical stimulation of the brain in young adults to enhance deep sleep and doubled their overnight memory,” the university explained.
In the study, Walker, lead author and postdoctoral fellow in psychology Bryce Mander, and colleagues studied 18 healthy younger adults, most of whom were under 30, and 15 healthy seniors, most of whom were over the age of 70. Each subject was asked to learn and complete tests on 120 word sets, and were then instructed to get a full night´s sleep while their brain wave activity was measured by an electroencephalographic (EEG) machine.
“The next morning, they were tested again on the word pairs, but this time while undergoing functional and structural Magnetic Resonance Imaging (fMRI) scans,” the statement said. “In older adults, the results showed a clear link between the degree of brain deterioration in the middle frontal lobe and the severity of impaired ℠slow wave activity´ during sleep.”
“On average, the quality of their deep sleep was 75 percent lower than that of the younger participants, and their memory of the word pairs the next day was 55 percent worse,” it added. “Meanwhile, in younger adults, brain scans showed that deep sleep had efficiently helped to shift their memories from the short-term storage of the hippocampus to the long-term storage of the prefrontal cortex.”