Earlier quoted context omitted.
Microtubules, maybe, but that's only one of a billion things going on in there. Here's a pretty decent article: http://www.nature.com/news/2011/110615/pdf/474272a.pdf My point is that a neuron is not an equation in a connection model. It's a cell. You can't hand-wave away its identity as such or all the things that happen in cells. Even if nothing quantum is involved (and I didn't say it was... we don't know), includ…
A cell is a physical system. A physical system can either: 1) Be sufficiently large that quantum effects are irrelevant, like a billiard ball, and thus it can be modeled deterministically inside of a computer. The Tegmark paper proposes this is how the brain works. 2) Rely on quantum mechanical effects (which are non-deterministic, but can still be simulated inside a computer if you trust a computer's opinion of "ran…
This misunderstands the role of quantum theory in macroscopic systems. There is never a scale so large that quantum effects can be safely ignored. All that happens is that the specific effects, and probabilities, change.
The Heisenberg Uncertainly principle doesn't build a wall between the microscopic and macroscopic realms, it makes a probabilistic prediction about quantum events at all scales -- larger scale, lower probability.
But a macroscopic system that has a very low probability of exhibiting classic quantum behaviors as a whole, will nevertheless show quantum behaviors at some level. An easily understood example is a radioactive sample -- let's say a kilogram of uranium. The sample isn't going to behave like Schrodinger's cat, but its constituent atoms certainly will.
In one sense, the uranium is a classical mass with no contribution from quantum theory. In another sense, it's highly influenced by quantum theory -- were this not so, there would be no nuclear disintegrations.
An observer can examine the sample and, intent on demonstrating that it's a classical system, use the half-life equation to predict its future --
a' = a 2^-t/f
a = activity level at time zero
a' = activity level at time t
t = time, consistent units
f = half-life factor
-- And the outcome looks very classical, but only because the sample is large. But the timing of the next disintegration is quantum-deterministic. So the uranium is a chimera -- part classical, part quantum. This is an example that makes the point very clearly, but all classical systems (and scales) possess quantum properties, usually not so obvious as it is with a radioactive sample.
> Rely on quantum mechanical effects (which are non-deterministic, but can still be simulated inside a computer if you trust a computer's opinion of "random").
Quantum effects aren't merely random. What connects an event to quantum theory isn't its randomness, but the nature of the randomness -- its genesis. No matter how carefully I design a random number generator, I won't be able to imitate quantum entanglement unless the system is actually capable of this specific physical behavior.