Sleep disorders reason for declining memory in old age?
Learned and experienced during the day is stored in long-term memory during the deep sleep phase. It seems like the brain’s memory is filled with information during the day that needs to be processed while sleeping. Conversely, lack of sleep affects the processing of information in the brain and favors memory loss, according to a team of researchers led by Bryce Mander from 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 impairments of the sleep phase, which in turn are due to changes in the brain. According to the researchers, the loss of gray matter in the forehead lobe can not disturb deep sleep, which in turn impairs the transmission of information from the hippocampus to long-term memory. In this way, memory is also weakened in old age, Mander and colleagues report in the journal "Nature Neuroscience".
Age-related loss of gray matter in the brain The brain study examines possible correlations between age-related loss of gray matter in the frontal lobe, the increased occurrence of sleep disorders and impaired memory in old age. From previous studies it was already known that deep sleep plays an important role in transferring memories into 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 area of the brain, which often shows a decrease in the gray matter of the brain in old age. The US researchers suspected a connection here. They therefore first analyzed how large the loss of gray matter in the elderly actually is and then checked whether changes in the sleep pattern of the elderly can be determined.
Disorders of deep sleep impair memory. The older test subjects (average age 72 years) had a reduced amount of gray brain substance 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, report Mander and colleagues. In order to determine 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 was learned was queried. During the sleep phase, the US scientists observed the subjects' brain activity, with special attention being paid to the delta brain waves. The researchers found that the subjects with a disturbed deep sleep phase remembered the word pairs after the test significantly less than study participants with normal sleep patterns. Her memory had benefited from sleep, but to a much lesser extent than among young adults.
Memory Improvement Through Better Deep Sleep? The current study results suggest that age-related impairment of deep sleep has a far more extensive effect on memory than previously thought. Not the age itself, but the disturbances of deep sleep would be decisive for the memory loss in old age. If the deep sleep of those affected could be improved again, this could also counteract the loss of memory, the US scientists hope. With medication and other therapeutic measures that positively influence deep sleep, mental retardation in old age would be possible. Although the study by the US scientists clearly shows a connection between the loss of gray matter in the brain, disturbed deep sleep and reduced memory in old age, it remains to be seen whether this is actually - as the researchers assumed - to be considered causal. (fp)
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