Edinburgh Science Festival 'Dreamachine' event puts 'reality' in spotlight

Audience members will be invited try out and share their experiences of the 'Dreamachine' - a device inspired by a 1959 invention by artist Brion Gysin.

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Prof Seth said: "It [Gysin's original design] was this simple contraption where you put a bright light in a turntable and cut-out cardboard with slits in it, but if you rotate the turntable at the right speed you get this flashing, stroboscopic light.

"If you sit in front of that, and it's bright enough, and you close your eyes, then pretty much everyone has surprisingly vivid visual and emotional experiences through colours and shapes.

"It's unexpected because your eyes are closed and the light isn't coloured - it's just white light - but this phenomenon has been known about for a very long time.

"The idea from a neuroscience perspective is that when your eyes are closed your brain is not expecting any visual input, but if the light is bright enough it can still activate the retina and if you stimulate the visual parts of the brain at their preferred frequency there's an amplification of the visual dynamics of the brain.

"It's almost as if the brain is looking at itself."

The phenomenon - known as stroboscopically-induced hallucination - was largely neglected until Prof Seth's lab at Sussex University began exploring it "in a backburner way" around a decade ago, before going on to recreate Gysin's Dreamachine "for the 21st Century" two years ago.

Music was added and it was converted into an immersive experience that could be shared by a group of people at once.

Since then it has been trialled on hundreds of volunteers, with "striking" results.

"Most people do experience geometric patterns and vivid colours and the visual field seems to be very expansive - it's almost like it goes round the back of their heads," said Prof Seth.

"Some people experience more complex things - they'll see objects and movie scenes unfolding. And some people don't get much, for whatever reason.

"But everybody has a unique experience, and the experience really does bubble up from within your own mind. It's bringing people back to a recognition about the power of their minds."

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Neuroscience has come a long way in untangling how the billions of neurons in the brain create our experience of the world, but exactly how - as Prof Seth puts it - "this mess of biological wetware gives rise to any kind of of conscious experience" remains one of science's greatest unsolved mysteries.

He favours the theory of the brain as a 'prediction machine' in which our perception of reality is based on the brain continually making predictions which are updated by sensory information.

It goes some way to explaining the tendency for people to 'see' what they expect.

Prof Seth said: "If I'm walking out of the door on a foggy morning and I'm expecting to see a friend, I might actually 'see' that friend - then get closer and realise it's someone else.

"We've done experiments in the lab showing that if you cue people - flash a word quickly like 'face' or 'house' in conditions where the image we show them is hard to see - then people will be more likely to see what they expect to see, and will see it more clearly and accurately if their expectation matches what is there."

Comparisons have been drawn between cracking the mystery of human consciousness and finding the elusive 'theory of everything' for the universe - something Stephen Hawking famously compared to "knowing the mind of God".

But Prof Seth rejects any suggestion that understanding human consciousness would detract from its wonder.

He said: "Of course some people cleave really strongly to the idea that they have a soul which contains their personality which will survive after the death of the body - that kind of belief is threatened by this way of thinking.

"But I think there's everything to gain and nothing to lose in terms of the way we understand ourselves in relation to the world.

"The self is not a thing perched somewhere inside the skull that does the perceiving; the self is itself a perception.

"The brain is constructing the experience of being in the same way that it's constructing the experience of the car across the road or the piano in the corner.

"Will we solve it though? - that's a big question.

"What I am confident about is that the nature of the mystery will change and we will understand a great deal more about what the self is and how our perceptions of the world come about."

'Consciousness: Machine of the Mind' is at the National Museum of Scotland, Thursday April 21