How Do We Fall Asleep?

It truly is amazing in this modern world, not only what we know but what we don’t know.  For instance, despite all of the advancements in our understanding of the human body, we still don’t know how we fall asleep.  Researchers are getting closer to finding out, with some help from fruit flies.

Fruit flies are widely used by scientists as a model organism to understand how biological mechanisms work in larger, more complex organisms like humans. In fact, the 2017 Nobel Prize for Medicine was awarded for discoveries concerning the body clock in flies.

Researchers at Oxford University are using the diminutive bugs to learn how specialist nerve cells in the brains trigger several key steps of falling asleep.

The team at Oxford’s Centre for Neural Circuits and Behaviour worked with a small cluster of neurons that had previously been shown to put flies to sleep when activated. When the flies are awake the sleep-control neurons are turned off. The longer the flies are awake, the more tired they become, which eventually reaches a tipping point and activates the neurons.

But the fact that the sleep-inducing neurons are only a tiny minority of all nerve cells posed a puzzle. Sleep entails some of the most profound and widespread changes our brains experience on a daily basis. How could so few cells control so much?

The team have found that the sleep-inducing cells ‘gate’ – or regulate the flow of electrical signals through – a node in the brain that is critical for all aspects of sleep: the fly’s motor system – controlling movement – was disconnected, preventing the animal from sleep-walking; the insect’s sensory thresholds were increased, making it less aware of its surroundings; and the ‘sleep debt’ or tiredness that had accumulated during waking was cleared.

Professor Gero Miesenboeck, Director of the Centre for Neural Circuits and Behaviour, said: ‘The sleep-inducing neurons act as a brake on the very brain cells whose activity causes tiredness. A beautifully simple system thus keeps sleep need and sleep in the balance.

‘We still don’t know why sleep debt builds up, what it consists of physically, how it triggers the switch to sleep and how the accumulated sleep debt is cleared. Finding the answers will help us solve the mystery of sleep.’

Source: Oxford University

 

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