In humans, REM sleep is thought to occur cyclically every 90 to 120 minutes across the night. But they do not experience the same physiological and behavioural elements that resemble REM dream sleep. Some jellyfish – who do not have a brain – do experience what could physiologically be characterised as sleep (shown by their posture, quietness, lack of responsiveness and rapid “waking” when prompted). Their brain activity and sleep stages align to some degree with human REM sleep. But such studies ultimately rely on self-reports of the dream experience.Īnything we spend so much time doing probably serves multiple ends.Īt the basic physiological level (indicated by brain activity, sleep behaviour and studies of conciousness), all mammals dream – even the platypus and echidna probably experience something similar to dreaming (provided they are at the right temperature). Brain imaging has indicated certain patterns of brain activity are associated with dreaming (and with certain sleep stages where dreams are more likely to occur).
It’s really hard to study dreaming because people are asleep and we can’t observe what’s going on. What do scientists know about REM sleep and dreaming? They might even help us imagine what’s possible during our waking hours. They wash the thoughts from the day’s events at a molecular level. If they’re strange or interesting dreams, you might tell someone else about them, which may further encode the dream memory.ĭreams and nightmares are mysterious and we’re still learning about them. When dreams or your alarm wake you, you’re likely coming out of dream sleep and your dream often lingers into the first few minutes of being awake. That’s usually because either really weird thoughts or feelings wake you up or because the last hour of sleep is nearly all REM sleep.
While this is not the only time your brain is potentially dreaming – we also dream during other sleep stages – it is the time your brain activity is most likely to be recalled and reported when you’re awake. About three or four hours will have been spent in light sleep.įor the remaining time, you were likely in rapid eye movement (REM) sleep. That’s because sleep changes with age and exercise affects brain activity. About one or two of these was likely in deep sleep, especially if you’re young or physically active. Last night you probably slept for seven to eight hours.
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