Golgi stained neurons in the dentate gyrus of an epilepsy patient. Image: WikiCommons
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Self-awareness by numbers

What is consciousness? In the past, this question was the preserve of theologians, psychologists and philosophers. Scientists seemed unable to find a way to probe the grey matter between our ears. Now that has changed. The study of the brain has experienced a renaissance.

We are in a moment similar to that when the telescope provided a way for the likes of Galileo to explore the outer reaches of the solar system. The development of the fMRI (functional magnetic resonance imaging) scanner, techniques of transcranial magnetic stimulation (TMS) and EEGs (electroencephalograms) has given scientists a way to ask the brain new questions. One of the most intriguing proposals to emerge is that mathematics might hold the key to unlocking the mystery of consciousness.

To understand what makes something conscious, one can look at the converse question of what contributes to things being unconscious. Every night, when we fall into dreamless sleep, our consciousness disappears. So what is happening in the brain that causes us to lose our sense of self until we wake or dream?

In the past, it was impossible to ask the sleeping, dreamless brain questions. New TMS techniques allow us to infiltrate the brain and artificially make neurons fire. By applying a rapidly fluctuating magnetic field to the brain, we can activate specific regions when people are awake and, more excitingly, when they are asleep. So how do the conscious and sleeping brains respond to this stimulation of neurons?

Experiments conducted by Giulio Tononi and his team at the Centre for Sleep and Consciousness at the University of Wisconsin-Madison have shown that the brain’s reaction to TMS when it is awake is strikingly different from when it is dreamlessly sleeping. The first part of the experiment involves applying TMS to a small region of the participants’ brains when they are awake or conscious. Electrodes attached to the head record the effect using EEG. The results show that different areas far away from the stimulated site respond to the stimulation at different times in a complex pattern that then feeds back to the original site of the stimulation. The brain is interacting as a complex, integrated network.

Participants are then required to fall asleep and, once in deep, “stage-four” sleep, TMS is again applied to the brain in the same location, stimulating the same region. Unlike in the conscious state, the electrical activity does not propagate through the brain. It’s as if the network is down. The tide has come up, cutting off connections. The implication is that consciousness has to do with the complex integration in the brain.

Our gut has as many neurons as our brain, yet we don’t believe it is conscious. Is this because the neurons are not wired to have this integrated feedback behaviour? Tononi has even developed a mathematical coefficient of consciousness that measures the amount of integration present in a network. Called “phi”, it is a measure that can be applied to machines as well as the human brain and offers a quantitative mathematical approach to what makes me “me”.

Could Tononi’s phi help us understand if a computer, the internet or even a city can achieve consciousness? Perhaps the internet or a computer, once it hits a certain threshold, might recognise itself at some point in the future. Consciousness could correspond to a phase change in this coefficient, rather like the way water can change state when its temperature passes the threshold for boiling or freezing.

If consciousness is a spectrum encoded by this coefficient, measuring from the consciousness of a stone to the consciousness of the human mind, who are we to say there might not be consciousness beyond where evolution has taken the brain? The fMRI scans that have been done on Tibetan monks as they meditate seem to show that the act of meditation takes them into an altered brain state that might well be an increased level of consciousness. The brain appears to be organised into two networks: the extrinsic network and the intrinsic – or default – network.

When people are performing tasks external to themselves, such as playing a musical instrument or filling the kettle, it is the extrinsic portion of their brain that is active. When individuals are reflecting more on themselves and their emotions, it the default network that appears to be more dominant.

The interesting observation is that these two networks are rarely fully active at the same time. One side of the see-saw needs to be down in order to allow the other side to play its part in enabling an individual to concentrate on whatever task is at hand. Yet evidence from scanning the Buddhist monks during periods of meditation indicates that they seem to be able to raise both sides of this neural see-saw at the same time.

The research opens up the thrilling possibility that there are ways to increase your levels of consciousness. And so, on 2 March, as part of the Barbican’s and the Wellcome Trust’s season “Wonder: Art and Science on the Brain”, I will be collaborating with the musician James Holden to see whether we can use music to take the collective phi of our audience and turn it up to 11.

Marcus du Sautoy is the Simonyi Professor for the Public Understanding of Science at the University of Oxford. “Wonder: Art and Science on the Brain” will run at the Barbican Centre, London EC2, from 2 March to 10 April


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