27 March 2018

Aging, sleep and neurons

Neurophysiologists could not explain why elderly people do not sleep enough

RIA News

Long-term observations of the brain of young and elderly rats did not reveal differences in the work of nerve cells that control sleep, which makes the mystery of sensitive senile sleep even more mysterious, say neurophysiologists in an article published in the Journal of Neuroscience (McKillop et al., Effects of aging on cortical neural dynamics and local sleep homeostasis in mice).

In recent years, scientists have again begun to argue about what is the aging process and the death of humans and animals. Some biologists and evolutionists believe that this process is not accidental and that it is controlled by a kind of "death program" – a certain set of genes that causes the body to become decrepit and die and thereby give way to a new generation of their own kind.

Other age-related changes, including short sleep duration in older people and animals, as scientists have recently discovered, may also be related to evolution. By falling asleep earlier than young people and waking up earlier and faster than them, the "grandfathers" and "grandmothers" of Homo sapiens ancestors could protect them from nocturnal predators and other threats.

Vladislav Vyazovsky, a neurophysiologist from Oxford University (UK), and his colleagues tried to find out what exactly makes older people wake up quickly and fall asleep hard by observing the brain work of three groups of mice – "teenagers" at the age of 5 months, one-year-old adults and two-year-old "old men".

As scientists have suggested, the sleep centers in the brain of elderly individuals gradually lose the ability to produce special waves, collective vibrations of nerve cells that are associated with the phases of deep and "normal" sleep. Because of this, the sleep of people and animals in age will not be as deep as in youth, and it will be easier for their sense organs to perceive signals from the outside.

Guided by this idea, the scientists compared the activity of nerve cells in the cerebral cortex of mice from these three groups, periodically depriving rodents of sleep for several days and then allowing them to sleep.

To the great surprise of Vyazovsky and his colleagues, they could not find any differences in the brain work of all three groups of mice – the cells of their cortex produced "sleep signals" in approximately the same way both with a normal daily routine and with excessively long wakefulness.

Similar conclusions, as noted by Vyazovsky (in a press release, Why does sleep become disrupted in old age? – VM), contradict what observations of the activity of the entire brain, and not individual neurons, show. According to the authors of the article, all this suggests that the secrets of senile sleep sensitivity are hidden somewhere else, which has yet to be found.

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