Out like a light: Scientists discover the brain’s ‘sleep switch’

October 8, 2018

Out like a light: Scientists discover the brain’s ‘sleep switch’ – and say it ‘could explain why you curl up under a warm blanket’ to nod off

Cluster of cells may become activated in the brains of mice before they nod off
Damage to these cells has previously been linked to insomnia in humans
Warm temperatures trigger these cells to become activated

By Alexandra Thompson Senior Health Reporter For Mailonline

Published: 13:02 EDT, 8 October 2018 | Updated: 13:04 EDT, 8 October 2018

Scientists have discovered a ‘sleep switch’ that may be essential to a decent night’s shut eye.

A cluster of cells in the region of the brain responsible for sleep becomes activated as mice are nodding off, according to a study by the Beth Israel Deaconess Medical Center.

As these cells become activated, chemical messengers within them start firing, which may send out a signal to the rest of the brain that it is time to sleep.

The study also found warm temperatures trigger this chemical messenger firing.

‘We thought this is why people need to curl up under a warm blanket to get to sleep,’ lead author Dr Clifford Saper said.

Scientists have discovered a ‘sleep switch’ that may be essential to getting shut eye (stock)

The researchers analysed a set of cells, called the ventrolateral preoptic nucleus, in a region of the brain in mice.

This brain region is known as the hypothalamus, which is responsible for shutting down ‘awake’ signals in the body.

Using genetically-engineered mice, the scientists activated the chemical messengers of these cells via a laser light beam.

In a second part of the experiment, a chemical was used to selectively activate some of these cells.

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Results from both parts of the experiment suggested that activating chemical messengers in these cells leads to sleep in mice.

This confirms previous research by the same scientists, which found these cells are active during sleep and damage to them results in insomnia.

But a 2017 paper by different researchers found the opposite – that stimulating these cells wakes an animal up.

CAN INSOMNIA BE PSYCHOLOGICAL?

Insomnia may be psychological, research suggested in May 2017.

Sufferers who take placebo pills feel more rested than those who get no treatment at all, according to a review of 13 studies.

According to the researchers, the simple act of taking a pill may ease the anxiety that makes it harder for some insomnia sufferers to fall asleep.

Dr Patrick Finan from Johns Hopkins University, who was not involved in the study, said: ‘Insomnia is shaped by expectation and perception, so it is not surprising that placebos, which implicitly alter expectation, are effective in improving perceptions of sleep.’

The researchers, from the University of Sydney, examined data from a total of 566 insomnia sufferers who were assigned to either receive a placebo that they believed was an active treatment or no pills at all.

Placebo patients reported greater improvements in their ability to fall asleep, the total amount of rest they got and their sleep quality.

Comparing placebo against recognised insomnia therapies can give inaccurate results as simply believing you are receiving a sleep-inducing treatment can ease the condition.

Study author Dr Ben Colagiuri, said: ‘The comparison with no treatment means that we can be sure that the improvement we observed was due to a genuine placebo effect, rather than being an artifact of simply taking part in a trial.’

Insomnia may be considered a condition of the mind due to one person averaging four hours sleep a night and feeling sufficiently rested, while another may get seven hours and feel the amount or quality of their shut eye is inadequate, Dr Finan explained.

In the more recent study, the scientists clear up the confusion.

‘We found that when the cells are stimulated one-to-four times per second, they fire each time they are stimulated, resulting in sleep,’ Dr Sapier said.

‘But if you stimulate them faster than that, they begin to fail to fire and eventually stop firing altogether.

‘We learned our colleagues in the other lab were stimulating the cells 10 times per second, which was actually shutting them off.’

In a separate part of the experiment, the scientists found warm temperatures trigger chemical messenger firing in these cells.

Dr Sapier added: ‘We thought this is why people need to curl up under a warm blanket to get to sleep.’

And continued activation of these cells caused the mice’s body temperature to fall by up to 5-to-6°C, the results added.

The study was published in the journal Nature Communications today.

Excessive cell activation may even be responsible for the prolonged sleep and decline in body temperature animals experience when they hibernate, the scientists add.

The researchers are investigating the link between sleep and body temperature in further studies.

In the human ‘body clock’, sleep occurs when a person’s body temperature falls by 1-to-2°C.

Insomnia affects around 60 million people in the US and up to 31 per cent of adults in the UK.

Research released last August suggested people who look after their teeth are less likely to suffer from lack of sleep.

Pensioners with less than 10 teeth often do not get the recommend seven hours of shut eye a night, with some getting by on less than four hours, a Japanese study found.

Missing teeth are thought to affect how the tongue lies in the mouth, which may lead to obstructive sleep apnoea (OSA), according to researchers from Tohoku University, Sendai.

OSA occurs when the walls of the throat relax and narrow during sleep, interrupting normal breathing.

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