Ever had a hallucination?  Did you know that you’re having one right now?

Our grip on reality is, according to neuroscientists, much less tangible than we believe. It seems our brain is largely guessing what’s going on around us, which it does by combining input from our senses with our expectations developed from previous experiences.

In fact, as University of Sussex neuroscientist Professor Anil Seth points out in his 2017 Ted Talk: “It’s only when we agree about our hallucinations that we call it reality.”

Such mysteries of the mind-brain are the focus of research at the University’s Sackler Centre for Consciousness Science, of which Professor Seth is a director.

As part of the Brighton Science Festival this month, two of the centre’s researchers, Dr David Schwartzman and Dr Keisuke Suzuki, will be demonstrating research straight out of the lab that both confirms and confounds our notions of what is – and isn’t – real.

Being Somebody will showcase interactive virtual reality (VR) that explores how our experiences of the world are shaped by our bodies and how bodily experience itself is actively constructed, moment-to-moment, by the brain.

For example, they will show easy it is for us to be momentarily fooled into believing that a fake limb, or even a fake body, could be part of ourselves. They will also give visitors a simulated taste of the trippy world of visual hallucinations.

While in normal life the balance between the brain’s expectations and sensory input works just fine, in some altered states – for example brought on through psychoactive drugs, or by mental disorders such as schizophrenia – perceptual hallucinations can become strange and disturbing.

To explore how and why these unusual hallucinations occur, Drs Suzuki and Schwartzman have combined Google’s Deep Dream algorithm, which is an artificial neural network that finds and enhances patterns in images, together with a virtual reality headset with 360-degree panoramic video of pre-recorded natural scenes to create what they are calling the ‘Hallucination Machine’.

The setup simulates the visual hallucinatory aspects of a psychedelic ‘trip’.  Anyone who puts on the headset is soon experiencing a weird world in which vivid hallucinations of dogs, cars and peacocks appear in the sky, on buildings, on humans – in fact, all over the panoramic view.

This is because the system was trained to categorise a thousand different types of images. The network looks for patterns that might resemble a dog within the image – in the same way that humans see faces and other images in meaningless patterns, such as clouds.

Dr Suzuki points out: “This is purely an engineering system. It’s not really modelling the brain but, there are a lot of similarities between the human visual system and this neural network.”

Importantly, the research may help clinicians to understand what’s happening in a neurophysiological sense during hallucinatory episodes.

Dr Schwartzman says: “It’s very difficult to get an accurate representation of what someone is hallucinating, but by using the Hallucination Machine those who have experienced these more other-worldly hallucinations can adjust the parameters of the network to more closely resemble their own experiences.

“This hopefully will give us a better understanding of what’s going on in altered states of consciousness.”

Being Somebody is on 17 February at the Sallis Benney Theatre as part of the Brighton Science Festival. For details, visit: http://www.brightonscience.com/