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Why Do We Sleep?

By TED:

Allah Almighty mentions to us in His Holy Book, the Qur’an: {And it is He who has made the night for you as clothing and sleep [a means for] rest and has made the day a resurrection.} (Surat Al-Furqan 25:47).

Did our modern lifestyle ruin our vital biological process of sleeping? Did the 21st century change our sleeping habits?

Russell Foster is a circadian neuroscientist: He studies the sleep cycles of the brain. And he asks: What do we know about sleep? Not a lot, it turns out, for something we do with one-third of our lives.

Foster studies sleep and its role in our lives, examining how our perception of light influences our sleep-wake rhythms.

Much as your ear does double duty (balance plus hearing), Foster posits that the eye has two jobs: creating vision, but also — as a completely separate function — managing our perception of light and dark, providing the clues that our circadian rhythms need to regulate sleep-wake cycles.

He and his team at the University of Oxford are exploring a third kind of photoreceptor in the eye: not a rod or a cone but a photosensitive retinal ganglion cell (pRGC) that detects light/dark and feeds that information to the circadian system.

As Foster explains: “Embedded within our genes, and almost all life on Earth, are the instructions for a biological clock that marks the passage of approximately 24 hours.”

Light and dark help us synchronize this inner clock with the outside world. The research on light perception hits home as we age — faced with fading vision, we also risk disrupted sleep cycles, which have very serious consequences, including lack of concentration, depression and cognitive decline.

The more we learn about how our eyes and bodies create our sleep cycles, the more seriously we can begin to take sleep as a therapy.

“Even in animals and people in whom the rods and cones used for vision have been completely destroyed and who are otherwise totally visually blind, the pRGCs can still detect light to shift the circadian clock.” — Russell Foster, in the Guardian

In the following talk, Foster shares three popular theories about why we sleep, busts some myths about how much sleep we need at different ages — and hints at some bold new uses of sleep as a predictor of mental health.


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