Lack of sleep as a cause of memory loss?

Sleep disorders Reason for diminishing memory in old age?

28/01/2013

During the deep sleep phase, what has been learned and experienced during the deep sleep phase is stored in the long-term memory. It seems like the brain's memory is filled with information during the day that needs to be processed during sleep. Conversely, sleep deprivation impairs the processing of information in the brain and favors memory loss, according to a research team led by Bryce Mander of the University of California at Berkeley.

The US scientists come to the conclusion that the age-related memory loss is at least partially caused by impaired sleep, which in turn is due to changes in the brain. The brain is not necessarily damaged by age, but the disappearance of gray matter in the frontal lobe can, according to the researchers disturb the deep sleep, which in turn impairs the transfer of information from the hippocampus in the long-term memory. In this way, the memory is weakened in old age, report Mander and colleagues in the journal „Nature Neuroscience“.

Age-related loss of gray matter
The brain study examines possible associations between the age-related loss of gray matter in the frontal lobe, the increased incidence of sleep disturbances, and the impairment of memory in old age. From previous studies it was already known that deep sleep plays an important role in transferring memories to long-term memory. The deep sleep phase is characterized by so-called delta brain waves, which originate from the medial prefrontal cortex (mPFC). The frontal lobe is also the brain area, which often shows a decrease in gray matter in old age. The US researchers suspected a connection here. Therefore, they first analyzed how large the loss of gray matter in older people really is, and then looked at whether there are any changes in the sleep pattern of the elderly.

Disorders of deep sleep affect the memory
The elderly subjects (mean age 72 years) had a reduced amount of gray matter in the medial prefrontal cortex compared to the control group of 18 young adults, which was associated with a lower activity of delta waves in deep sleep, Mander and colleagues report. To assess the effects of these impairments of deep sleep, the researchers subjected the study participants to a test in which they should learn word pairs in the evening. After ten minutes and after an eight-hour sleep phase, what they had learned was queried. During the sleep phase, the US scientists observed the brain activity of the subjects, with particular attention to the delta brain waves. The researchers found that the subjects with disturbed deep sleep phase after the test could remember significantly worse the word pairs, as study participants with normal sleep pattern. Although her memory had benefited from sleep, to a much lesser degree than young adults.

Improvement of memory through better deep sleep?
The current study results suggest that age-related impairments of deep sleep have a far more extensive effect on memory than previously thought. Not the age itself, but the disturbances of deep sleep would therefore be decisive for the loss of memory in old age. If the deep sleep of those concerned improves again, this could possibly also counteract the loss of memory, so the hope of the US scientists. With drugs and other therapeutic measures that affect the deep sleep positive, therefore, a delay of mental degradation in old age would be possible. Although the study of the US scientists clearly shows a connection between the loss of gray matter, the disturbed deep sleep and the declining memory in old age, it remains to be seen whether this is actually - as the researchers suggest - as causal. (Fp)

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Picture credits: Sergej23