sciencealert | When it comes to dreamlessness, conventional wisdom states that consciousness disappears when we fall into a deep, dreamless sleep.
But researchers have come up with a new way to define the different ways that we experience dreamlessness, and say there’s no evidence to suggest that our consciousness 'switches off' when we stop dreaming. In fact, they say the state of dreamlessness is way more complicated than we’d even imagined.
"[T]he idea that dreamless sleep is an unconscious state is not well-supported by the evidence," one of the researchers, Evan Thompson from the University of British Columbia in Canada, told Live Science.
Instead, he says the evidence points to the possibility of people having conscious experiences during all states of sleep - including deep sleep - and that could have implications for those accused of committing a crime while sleepwalking.
But first off, what exactly is dreamlessness?
Traditionally, dreamlessness is defined at that part of sleep that occurs between bouts of dreams - a time of deep sleep when your conscious experience is temporarily switched off. This is different from those times when you simply cannot remember your dreams once you've woken up.
As dream researchers from the University of California, Santa Cruz explain, most people over the age of 10 dream at least four to six times per night during a stage of sleep called REM, or Rapid Eye Movement. (Studies suggest that children under age 10 only dream during roughly 20 percent of their REM periods.)
Considering REM periods can vary in length from 5 to 10 minutes for the first REM period of the night to as long as 30-34 minutes later in the night, researchers have suggested that each dream is probably no longer than 34 minutes each.
While there's some evidence that we can dream during the non-REM sleep that occurs 1 or 2 hours before waking up, if you’re getting your 7 hours of sleep each night, that still leaves a lot of room for dreamlessness.
Thompson and his colleagues suggest that the traditional view of dreamless as being an unconscious state of deep sleep is far too simplistic, arguing that it's not a uniform state of unconsciousness, but actually includes a range of experiences involving certain stimuli and cognitive activity.