With its tangled networks of neurons and synapses, the brain is one of the most complex systems known. No computer can match it’s processing power. There are two differences between the brain and a computer – memory and processing speed. A computer has a fat big memory than the brain. But the brain wins hands down at speed learning. Humans can spot a person in a crowd a lot quicker than any automaton. The brain’s processing power is hundreds of thousands of times greater than the most advanced computer chips. Yet signals in the brain are transmitted at a relative snail’s pace up to six orders of magnitude slower than digital signals. As a result of these different speeds, the brain has a hierarchical structure, built up from many layers that talk to one another. Computers have essentially one layer, churning through millions of calculations to beat human grandmasters at chess, for instance.
How might computations in the brain give rise to consciousness? It’s hard to define what consciousness is exactly. But it is how we experience life. We have a sense of present and we have a sense of the passage of time, the past. Our brain stores memories, and we assign patterns to them to give meaning. We Can make simple predictions about the future, through which we make decisions. Many physicists including the quantum pioneers Niels Bohr and Erwin Schrodinger, have thought that biological systems including brain might behave in ways that are indescribable using classical physics. As quantum theory developed, a number of ways of creating consciousness have been proposed from collapsing wavefunctions to entanglement. But we are still far from learning exactly how this works.
David Bohm asked what happens when we listen to music. As the tune rolls along, we retain a memory of its evolving shape and combine that recollection with our sensory experience of the present, the sounds, chords and feelings of the music we are hearing now. It is this blend of historical pattern with our canvas of the present that is our experience of consciousness. Bohm argued that this coherent narrative stems from the underlying order of the universe. Just as photons are both waves and particles and we observe one from under different circumstances, so mind and matter are projections onto our world of deeper order. They are seperate aspects of life being complementary looking at matter tells us nothing about consciousness, and vice versa.
Quantum Brain States:
In 1989, the Oxford mathematician and cosmologist Roger Penrose published one of the most controversial ideas for how consciousness arises in ‘The Emperor’s New Mind’. Penrose revisited Turing’s ideas and argued that the human brain is not a computer. Moreover, the way it operates is fundamentally different and no computer could ever replicate it using logic alone. Penrose went several big steps further, by proposing that consciousness is linked to fluctuations in spacetime due to quantum gravity. Most physicists didn’t like it, why should quantum gravity apply to a soft, wet, gelatinous brain? The artificial intelligence community didn’t like it, as they believed they would one day build a powerful brain simulator.
Penrose didn’t know exactly how or where the brain handled these quantum gravity effects. He teamed up with the anaesthesiologist Stuart Hameroff to extend the model, elaborated in Penrose’s 1994 book ‘Shadows of the Mind’. The conscious mind they suggested was made up of many superposed quantum states, each with its own spacetime geometry. The states decay as events unfold, but they didn’t all do so instantaneously. This momentary awareness is our feeling of consciousness. Quantum gravity acts at very tiny scales, smaller than a neuron. Hameroff suggested that this could take place in long polymer structures that lie within neurons and other cells called microtubules. Microtubules provide scaffolding and they also shepherd neurotransmitting chemicals.
Bose-Einstein condensate, wavefunction collapse and the interface between the observer and the observed have been explored as consciousness triggers. And quantum field theory has also been explored as a means of describing brain states. Memory states may be described as many particle systems, a bit like the virtual sea of particles that are associated with quantum fields and empty space. Quantum tunnelling may help along the chemical reactions involved in neuronal signalling.
Others physicists have suggested that quantum randomness underlies consciousness, jolting us sequentially from one mindful state to another. Many physicists remain sceptical, though, and have queried whether quantum states could exist in the brain for any length of time. In 1999 paper, the physicist Max Tegmark suggested that decoherence effects would dissemble quantum states on a timescale much shorter than that characteristic of brain signalling. The brain is too big and hot to be a quantum device. So the jury is definitely out on the degree to which quantum theory explains consciousness.