Poor sleep prevents the aging brain from storing information
The relationship between symptoms accompanying aging, such as poor sleep, memory loss and deterioration of the brain, has so far remained unclear. Neuroscientists at the University of California at Berkeley, working under the guidance of Associate Professor Matthew Walker, for the first time found a commonality between these common age-related disorders. They found that the so-called slow waves of brain activity generated during deep restorative sleep, which young people usually fall into, play a key role in transferring memories from the hippocampus – the region of the brain that provides their short–term storage - to the prefrontal cortex, which acts as a "hard disk" for longer storage.
Healthy adults usually spend about a quarter of a night's sleep in the deep slow sleep phase. Slow waves of brain activity are generated in the middle part of the frontal lobe of the brain. Apparently, the deterioration of this region of the brain in elderly people is associated with their inability to fall into deep sleep. As a result of the poor quality of slow sleep, memories "get stuck" in the hippocampus and new information is recorded on top of them the next day. This may explain the forgetfulness of older people, including the difficulties experienced by many of them with remembering people's names.
As part of the study, scientists tested the memory of 18 healthy young people (mostly aged 20-30 years) and 15 healthy elderly people (mostly older than 70 years) after a full night's sleep. The day before, before going to bed, all participants learned 120 pairs of words and were tested for their memorization.
At night, the researchers used an electroencephalograph to record the activity of brain neurons, which determined the duration of different phases of sleep.
The next morning, the participants again passed a test for the quality of memorization of the pairs of words learned the day before, and this testing took place during functional and structural magnetic resonance imaging.
The obtained results demonstrated the existence of a clear relationship between the degree of deterioration of the condition of the middle part of the frontal lobe of the brain and the violation of the formation of slow waves during sleep in elderly people. On average, the quality of their deep sleep was 4 times lower than the sleep quality of the young study participants, and their ability to recall the pairs of words learned the day before was almost 2 times (55%) worse.
The results of the tomography indicated that deep sleep contributed to the transfer of memories from the hippocampus for long-term storage in the prefrontal cortex.
These data open up new possibilities for therapeutic interventions aimed at combating age-related memory loss. The formation of slow waves of brain activity can be caused by transcranial electrical stimulation or pharmacological drugs. There is evidence that German neuroscientists with the help of electrical stimulation managed to prolong the slow sleep phase of young people, which doubled their ability to remember during the night. The authors are already planning to conduct a similar study with the participation of elderly people.
Article by Bryce A Mander et al. Prefrontal atrophy, disrupted NREM slow waves and impacted hippocampal-dependent memory in aging is published in the journal Nature Neuroscience.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of California – Berkeley:
Poor sleep in old age prevents the brain from storing memories.
29.01.2013