Sleep, more complicated than you'd think

Photo by Nomao Saeki

Photo by Nomao Saeki, obtained under Creative Commons Zero license

We spend one third of our lives asleep, but few of us clearly remember what we dream about, or even if we dream at all. It's always been believed that you're conscious when you're awake, and this consciousness fades away as you drift into deep sleep. But what if you could retain consciousness in your sleep, remember your dreams and even decide what happens in them?

New research is challenging our long-held assumptions about dreamless sleep and consciousness. Monash University's Dr Jennifer Windt has co-authored a paper ‘Does Consciousness Disappear in Dreamless Sleep?‘ (published in Trends in Cognitive Sciences) together with Evan Thompson of the University of British Columbia, and Tore Nielsen of Université de Montréal.

In the paper the researchers argue that consciousness exists on a spectrum between wakefulness and sleep, and that our current view of dreamless sleep as uniformly unconscious is an oversimplified one – not least because there's no concrete definition of dreaming and dreamlessness. 

“Until recently, there was no agreement on how best to use the concept of dreaming itself,” said Dr Windt, a lecturer at Monash's School of Philosophical, Historical and International Studies, and author of Dreaming (2015).

Dr Windt explained that the idea for criticising the current assumptions around dreamless sleep came from a book chapter in co-author Evan Thompson’s book Waking, Dreaming, Being, and the exchange between Thompson and Dr Windt in Open Mind. From this initial idea the researchers broadened their argument to include memory consolidation and sleep behaviour. 

Criticising the assumption that dreamless sleep is uniformly unconscious, and that conscious experience in sleep is exhausted by dreaming, Dr Windt and her colleagues argue that a more precise taxonomy for describing dreamful and dreamless sleep has consequences for investigating the sleep-stage and neural correlates (the minimal set of neuronal events needed for consciousness) of conscious experience.

Dr Windt and her fellow authors suggest that what happens when we sleep is more complicated than we’d imagined, and Dr Windt said she hopes the paper can help to inform other specific areas of sleep research. 

“Sleep disorders, including sleep behaviour and sleep state misperception, for example in insomnia, is another area where an improved understanding of the relationship between sleep conscious experience might lead to improved diagnostic criteria and therapeutic measures (such as mindfulness and insomnia),” said Dr Windt.

And the research could even impact the legal system and those who commit violent crimes whilst asleep, because how someone experiences dreamless sleep could affect their culpability for violent behaviour in NREM sleep. Some researchers argue that the only way someone could be excused for such violent behaviours was to demonstrate a total lack of consciousness and a complete lack of recall.

“We think, however, that this requirement might be too strong. It is not at all clear that NREM sleep behaviour can simply be described as unconscious automatisms—essentially as zombie-like behaviour,” said Dr Windt.

“The relation of these behaviours to different forms of conscious experience is just not well enough understood at this point. But it suggests that even if violent behaviours arising from NREM sleep are associated with some form of conscious experience and recall, this might not be enough for holding the person responsible.” 

The issue of responsibility for NREM sleep behaviour might still be an open question but Dr Windt is of the opinion that it will be an area where an improved understanding of the relationship between sleep behaviour and conscious experience could have implications beyond philosophy and science. 
As well as entering the mainstream, dreaming is now being discussed in the context of the debate on the neural correlates of consciousness.

Dr Windt said her research, with co-authors Evan Thompson and Tore Nielsen, can help to inform this debate,  “because it suggests that simple or perhaps even minimal forms of phenomenal experience can exist in dreamless sleep, whereas dreaming seems to involve a more complex, immersive kind of experience. Our proposal for a refined taxonomy can therefore help identify new and hopefully more precise targets for investigating the neural correlate of conscious states.” 

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