Scientists identify the switch that says it's time to sleep

February 19, 2014
Credit: Maurajbo/Wikipedia.

The switch in the brain that sends us off to sleep has been identified by researchers at Oxford University's Centre for Neural Circuits and Behaviour in a study in fruit flies.

The switch works by regulating the activity of a handful of sleep-promoting nerve cells, or , in the brain. The neurons fire when we're tired and need sleep, and dampen down when we're fully rested.

'When you're tired, these neurons in the brain shout loud and they send you to sleep,' says Professor Gero Miesenböck of Oxford University, in whose laboratory the new research was performed.

Although the research was carried out in fruit flies, or Drosophila, the scientists say the sleep mechanism is likely to be relevant to humans.

Dr Jeffrey Donlea, one of the lead authors of the study, explains: 'There is a similar group of neurons in a region of the human brain. These neurons are also electrically active during sleep and, like the flies' cells, are the targets of general anaesthetics that put us to sleep. It's therefore likely that a molecular mechanism similar to the one we have discovered in flies also operates in humans.'

The researchers say that pinpointing the sleep switch might help us identify new targets for novel drugs – potentially to improve treatments for .

But there is much still to find out, and further research could give insight into the big unanswered question of why we need to sleep at all, they say.

'The big question now is to figure out what internal signal the sleep switch responds to,' says Dr Diogo Pimentel of Oxford University, the other lead author of the study. 'What do these sleep-promoting cells monitor while we are awake?

'If we knew what happens in the brain during waking that requires sleep to reset, we might get closer to solving the mystery of why all animals need to sleep.'

The findings are reported in the journal Neuron. The work of the Centre for Neural Circuits and Behaviour is funded by the Wellcome Trust and the Gatsby Charitable Foundation. This study was also supported by the UK Medical Research Council, the US National Institutes of Health, and the Human Frontier Science Program.

The body uses two mechanisms to regulate sleep. One is the body clock, which attunes humans and animals to the 24 hour cycle of day and night. The other mechanism is the sleep 'homeostat': a device in the brain that keeps track of your waking hours and puts you to sleep when you need to reset. This mechanism represents an internal nodding off point that is separate from external factors. When it is turned off or out of use, sleep deficits build up.

'What makes us go to sleep at night is probably a combination of the two mechanisms,' says Professor Miesenböck. 'The body clock says it's the right time, and the sleep switch has built up pressure during a long waking day.'

The work in allowed the critical part of the sleep switch to be discovered. 'We discovered mutant flies that couldn't catch up on their lost sleep after they had been kept awake all night,' says Dr Jeffrey Donlea.

Flies stop moving when they go to sleep and require more disturbance to get them up. Sleep-deprived flies are prone to nodding off and are cognitively impaired – they have severe learning and memory deficits, much as in humans leads to problems.

Professor Miesenböck says: 'The sleep homeostat is similar to the thermostat in your home. A thermostat measures temperature and switches on the heating if it's too cold. The sleep homeostat measures how long a fly has been awake and switches on a small group of specialized cells in the brain if necessary. It's the electrical output of these nerve cells that puts the fly to sleep.'

In the , the researchers were able to show a key molecular component of the electrical activity switch is broken and the -inducing neurons are always off, causing insomnia.

Explore further: Drowsy Drosophila shed light on sleep and hunger

More information: 'Neuronal Machinery of Sleep Homeostasis in Drosophila' by Jeffrey Donlea, Diogo Pimentel and Gero Miesenböck is to be published in the journal Neuron on Wednesday 19 January 2014.

Related Stories

Drowsy Drosophila shed light on sleep and hunger

October 3, 2013

Why does hunger keep us awake and a full belly make us tired? Why do people with sleep disorders such as insomnia often binge eat late at night? What can sleep patterns tell us about obesity?

Sleep to protect your brain

December 31, 2013

A new study from Uppsala University, Sweden, shows that one night of sleep deprivation increases morning blood concentrations of NSE and S-100B in healthy young men. These molecules are typically found in the brain. Thus, ...

New fruitfly sleep gene promotes the need to sleep

February 4, 2014

All creatures great and small, including fruitflies, need sleep. Researchers have surmised that sleep – in any species—is necessary for repairing proteins, consolidating memories, and removing wastes from cells. But, ...

Feeling sleepy? Maybe your brain's too full

February 6, 2014

Sleep is an essential state of the brain but why do animals risk the vulnerability that comes with not being conscious for hours? What happens in the brain during sleep that's so vital for life?

Recommended for you

Umbilical cells help eye's neurons connect

November 24, 2015

Cells isolated from human umbilical cord tissue have been shown to produce molecules that help retinal neurons from the eyes of rats grow, connect and survive, according to Duke University researchers working with Janssen ...

Brain connections predict how well you can pay attention

November 24, 2015

During a 1959 television appearance, Jack Kerouac was asked how long it took him to write his novel On The Road. His response – three weeks – amazed the interviewer and ignited an enduring myth that the book was composed ...

No cable spaghetti in the brain

November 24, 2015

Our brain is a mysterious machine. Billions of nerve cells are connected such that they store information as efficiently as books are stored in a well-organized library. To this date, many details remain unclear, for instance ...

Neurons encoding hand shapes identified in human brain

November 23, 2015

Neural prosthetic devices, which include small electrode arrays implanted in the brain, can allow paralyzed patients to control the movement of a robotic limb, whether that limb is attached to the individual or not. In May ...

Wireless sensor enables study of traumatic brain injury

November 23, 2015

A new system that uses a wireless implant has been shown to record for the first time how brain tissue deforms when subjected to the kind of shock that causes blast-induced trauma commonly seen in combat veterans.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.