(Transcript from SBS World News Radio)
Sleepwalking, comas, locked in syndrome and anaesthesia.
There have been significant gains in our scientific understanding of consciousness, but exactly how it works - and what it is - remains a mystery.
John MacFarlane asks whether we can know for certain if someone is conscious or not.
(Click on the audio tab above to hear the full report)
When Rosie Harrison's two and a half year old son came out of anaesthesia after having his tonsils and adenoids out, he was, she says, demonic.
"He just came out and was thrashing about and screaming and carrying on. ⦠He was looking at me but through me. Yeah, it was a really vacant sort of gaze and he was screaming out mummy, and he wanted his mum and I'm going it is mum. ⦠It was like there was someone else in there, it wasn't my son."
Anaesthetists call this emergence delirium.
They say it happens to 5 to 10 per cent of preschool children.
But they don't know exactly why it happens, in part because they don't know exactly how anaesthesia affects consciousness.
Doctor Andrew Davidson is an anaesthetist at the Royal Children's Hospital in Melbourne.
He says part of the issue is that there's no firm understanding of consciousness itself.
"We're not really sure what the neurological or the biology of consciousness is, so it's hardly surprising that we don't really know how anaesthetics work, given that our job is to make someone unconscious but we don't really know what consciousness is or where the consciousness actually resides in the brain."
There's a race within the worlds of neuroscience, medicine, biology and philosophy to define and understand consciousness.
But until that race ends, the inner workings of things like anaesthesia, sleepwalking, and comas, remains a mystery.
Joel Pillar says his partner Alex Rogers often sleepwalks several times a week.
"She 'sleep eats' a lot, so she'll just wake up in the morning and there will be a bunch of wrappers or a bowl of cereal half eaten or something on the ground and she won't remember anything about it. But probably the thing that worries me is when she sleep walks out of the house and so sometimes I'll wake up just having heard the front door close and I'll jump out of bed and run after her and she'll be down the street."
Alex says she only remembers some of the events.
"I don't know that I've done it but quite often if something triggers my memory, I have like a vague recollection, especially with the sleep eating, I'll wake up and I'll see like the cereal and I can have this vague recollection of being in the kitchen and doing that but quite often if I don't have that trigger I won't remember it. I won't remember at all."
Doctor Nao Tsuchiya, a computational neuroscientist at Monash University, says sleepwalking may show that memory and consciousness are separate things.
"So consciousness and memory tend to go together, when you're conscious, when you're awake you remember well. When you are not conscious you don't remember. But also disassociation happens. You have consciousness but no memory and you can also have a memory without consciousness so these two things are completely different things so you shouldn't mix it up. And in that sense there is a, one possibility is that these people are actually fully conscious but don't remember anything later on. Another possibility is that they are doingvery complex things and they don't remember and they don't feel anything."
Mary-Louise Clifford had a pulmonary embolism last year, followed by a heart attack.
When efforts were made to revive her from an induced coma, she was unresponsive for several days.
But she has vivid memories from that time.
"I remember being in the back of the ambulance and the conversation that the ambulance drivers speaking to the hospital. Then there's nothing for a while and then I thought I was at a party trying to video people coming in and out of the party from underneath a canopy of a boat."
Kate Allatt had a stroke in 2010 and remembers nothing from her time in an induced coma.
When she woke up, she couldn't move at all.
Worse, nobody knew that she was conscious.
"All I could do was see and hear and they became very acute. I could feel anybody touching me. So the messages going from my say my hand to my brain to say I was being touched, but my brain couldn't instruct any part of my body, my eyelids, my eyes, my legs, my digits, anything to move. ⦠it was utterly horrendous, it was, it was - it was like being buried alive"
Doctor Tsuchiya says situations like Kate's show that we require more than observational methods to evaluate consciousness.
"But what is pretty clear from the description of persons who had this locked in syndrome is the consciousness completely independent of the input to the brain and also output from the brain. What's inside the brain is generating it, that's why she couldn't move any of the muscles but she was completely aware of everything, right? So any kind of assessment or any kind of measurement that relies on input side or outside side, motor behaviour, is going to fail, I'm pretty sure it's not going to work"
Doctor Tsuchiya believes that we're on our way to being able to measure consciousness.
Others, like Doctor Davidson, aren't so sure.
"I think we can tell when people are unconscious most of the time but I still think that we don't really understand, we understand a lot of the neurobiology of consciousness and how the brain works but we don't understand enough to be able to measure something which will guarantee exactly what consciousness is."
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