Adventures in sleep
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What does our brain actually do during sleep?
What happens to our brain at night? Today we hear some intriguing and at times bizarre tales of nightmares, night terrors and sleepwalking.
Jackie began to become aware that she was undertaking other behaviours in her sleep as well. On one occasion she greeted her then landlady in the morning and the landlady said to her, where were you going on your motorbike at one in the morning? to which Jackie was completely bewildered and it became apparent that actually she was riding her motorbike in her sleep.
Hello, you're with All In The Mind on RN. I'm Lynne Malcolm. Dr. Guy Lesch-Zinner is a consultant neurologist and sleep physician at Guy's and St. Thomas hospitals in London. He's fascinated by the field of sleep medicine because he says it describes the various states of our brain. His book, The Nocturnal Brain, illustrates the neuroscience behind our sleep. But before we delve into this secret world of sleep, why is it that we sleep at all? Guy Lesch-Zinner.
The very short answer is we don't fully understand why we sleep. We know that sleep has probably a variety of purposes. It's important for the regulation of the brain. It's also important for regulation of the body and it has a broad range of influences on our health, physical, psychological and neurological. We think that one of the very important functions of sleep is in housekeeping of the brain. So we know that there are a number of important chemical and electrical changes within the brain during sleep that have a wide range of influences including the removal of toxins and metabolites from the brain but also reconfiguring connections between various neurons in the brain to allow us to learn, important for our memory, for our emotional processing.
And we know that also sleep is important for the regulation of our psychological health. So if you disrupt sleep and there remains some uncertainty about whether one stage of sleep is more important than another for this, we know that this can have really quite negative consequences on our mood and on our levels of anxiety as well.
Guy Lesch-Sinner has encountered and treated many unusual sleep disorders in his clinical work in London. First, though, he explains the normal pattern of human sleep.
We know that sleep is not a static state. It's not an on or off situation. And as we drift off to sleep and stay asleep over the course of the night, we fluctuate through various what we term stages of sleep. Sleep in humans tends to be divided into two different overriding stages. So that of REM sleep or rapid eye movement sleep. This is what historically we referred to as dreaming sleep because it was the stage of sleep during which if you were awoken, that is when people would describe these dreams of a narrative structure, what we really understand as dreams.
Why do we sleep and what are its main functions?
But we also now know that certain forms of dreaming occur in non-REM sleep, so in the stage of sleep during which our eyes don't move back and forward. We tend to divide non-REM sleep into three stages of sleep, so light sleep, intermediate sleep, and deep sleep. So over the course of the night, what typically tends to happen, in adults at least, is that we gradually drift off into the deeper stages of non-REM sleep over about half an hour, reaching very deep sleep after about 30 minutes. And then that non-REM sleep usually lightens before we then go into our first cycle of REM sleep, usually about an hour to an hour and a half after sleep onset. Over the course of the night, we then cycle probably four or five times usually.
And as we go through the night, the stages of deep sleep tend to lessen in terms of depth, and the amount of REM sleep, of rapid eye movement sleep, tend to extend. So we do the majority of our deep non-REM sleep in the first half of the night, and the majority of our REM, or what used to be termed dreaming sleep, in the latter half of the night.
Most of us are familiar, at least, with the concept of sleepwalking. But one of Gailesh Sinha's patients takes walking in one's sleep to another level completely.
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Chapters
6 chapters
1
What does our brain actually do during sleep?
0:06–3:24
2
Why do we sleep and what are its main functions?
3:24–8:19
3
How are REM and non‑REM sleep stages different and why do they matter?
8:19–14:27
4
What are sleepwalking and other non‑REM parasomnias and how do they occur?
14:27–20:29
5
How can extreme sleep behaviors like sleep‑driving be treated?
20:29–25:56
6
What causes REM‑related disorders such as REM‑behavior disorder and cataplexy?
25:56–28:19