282 Are the Androids Dreaming Yet?
Roger Penrose is fascinated by such counterfactual experiments and is inspired to think such effects might have a role in non-computable thought. It is his ‘machines’ we will look at next.
Penrose-Hameroff Machines, aka Brains
Roger Penrose of Oxford University and Stuart Hameroff of the University of Arizona have proposed a very different way to understand the workings of the brain. They focus on the much smaller scale structures within neurons called tubulin microtubules. If you watch a brain form, the dendrites grow towards each other, twisting and turning rather like the growth of a plant as viewed in a slow motion nature film. This motion is controlled by micro-tubular structures formed of a protein called tubulin. Tubulin is made from peanut-shaped polar molecules that self- assemble into helical tubes with a radius of just seven molecules. The tubes bundle together to form the backbone of neurons. The peanut- shaped molecules are bipolar switches and can flip between two states. This allows them to bend into different shapes and, in the most extreme example, to flap fast enough to propel small organisms such as paramecia. It is also, interestingly, the protein that unzips the double helix when a cell divides, and so plays a fundamental role in our evolution.
Penrose and Hameroff suggest these tubes form the true processing element in our brains. The walls of the tubes are formed of successive alpha and beta tubulin molecules. Each of the tubulin molecules can flip between two states, propagating a ripple along the tube wall. The scale is small enough for quantum effects to matter, and Hameroff suggests quantum error correction keeps the ripples from decohering too fast. Because the processing is happening at a molecular level rather than at the scale of a neuron, the brain would be considerably more powerful than a count of its neurons would suggest. They propose increased computing power would stem from three sources: There are many more tubulin molecules than neurons; the micro-tubes could perform quantum computation, and the micro-tubes are capable of non- computable, conscious, thought.
Measurement of a quantum process is the only candidate we have for a non-deterministic physical process today; all other physical processes are deterministic. Penrose argues that quantum processing in the brain spontaneously collapses in decision making because of the interaction between quantum superposition and gravity. The arguments are put forward in two books: The Emperor’s New Mind and Shadows of the Mind. This theory remains controversial for two main
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