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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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