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I think the key fail is hidden beneath this statement, 'many “digital” computer switches are built out of analog components and processes'. In fact obviously, a

by themgt 11y ago

I think the key fail is hidden beneath this statement, 'many “digital” computer switches are built out of analog components and processes'. In fact obviously, all computers are built out of analog components, in the sense that the entire universe is analog. However, this is the problem. Computers are designed to interpret or translate the messy analog world where nothing is exactly 1 or 0, into a precise, deterministic digital world where everything is either 1 or 0. And I think it's highly likely that the brain does not work in this manner whatsoever, and that in fact, in the translation of reality into 1s and 0s, you've lost far too much to properly "compute consciousness" Would it be possible to build a synthetic brain out of some form of "analog computer", capable of consciousness? Almost certainly. But since we have no idea what sort of architecture or paradigm that would use, or how we would program it or whether it would even "execute instructions" in a way remotely similar to digital computer software, such a declaration becomes meaningless.

linschn 11y ago
You can approximate any analog value to arbitrary precision using a (by nature binary) Turing Machine, therefore you can bring the loss of information as low as needed. The question is whether the brain offers a more complete framework than all the models of computation we know today (which are equivalent to one another). To put it another way : is there a function that the brain can compute that a Turing Machine cannot. We know of no such function now, but have ruled out yet that there is none, although most computer scientist agree with the Church-Turing hypothesis.
- themgt 11y ago
  But this is effectively begging the question. If you assume that reality can be completely described by functions that compute on natural numbers, then obviously anything within reality, including consciousness, can be simulated by a Turing machine. Unless I've missed something, it's not actually been shown that the universe itself is Turing-computable, therefore there's no reason to assume everything within the universe could be equivalently simulated on a Turing machine. It could also be that in theory, consciousness is Turing computable, but not in practice. For example just computing a protein fold for 1 millisecond takes hundreds of ASICs days of compute time. This might give some clue that complex physical wetware processes are not able to be efficiently simulated in real time on any realistic Turing machine.
coldtea 11y ago
>in the sense that the entire universe is analog. Citation needed.
electrograv 11y ago
> And I think it's highly likely that the brain does not work in this manner whatsoever, and that in fact, in the translation of reality into 1s and 0s, you've lost far too much to properly "compute consciousness" You act as though the only datatype usable by computers is bool. That's ridiculous. Yes, computers are binary, but they can compute analog things just fine via floating or fixed point arithmetic to arbitrarily high precision, among many other things. To claim that the brain has a fundamental advantage over a Turing machine is to claim that there's some magical quantum (or otherwise) advantage in the brain's physical system that is un-simulate-able by a Turing machine. You can't even argue that analog provides superior precision to digital representation of continuous values, because the analog part of the brain is represented with discrete units (accumulation of neurotransmitter molecules in various parts of the neuron)! In other words, our brain actually uses fixed point math (granted, incredibly complicated fixed point math :))
- themgt 11y ago
  > To claim that the brain has a fundamental advantage over a Turing machine is to claim that there's some magical quantum (or otherwise) advantage in the brain's physical system that is un-simulate-able by a Turing machine. Again, please point to any research you know of indicating that the universe itself is fully Turing-computable.
  - guard-of-terra 11y ago
    Universe doesn't have to be, just neurons and other brain hardware. Of course you can always see quantum phenomena affecting outcome, you just have to rule those out as neligible / much lower than noize threshold.
    - sgt101 11y ago
      There are many functions which cannot be computed on a Turing Machine. https://en.wikipedia.org/wiki/Computable_function#Uncomputable_functions_and_unsolvable_problems https://en.wikipedia.org/wiki/Computable_function#Uncomputab...
jwmerrill 11y ago
> Computers are designed to interpret or translate the messy analog world where nothing is exactly 1 or 0, into a precise, deterministic digital world where everything is either 1 or 0. And I think it's highly likely that the brain does not work in this manner whatsoever But neurons totally do work by encoding information with discrete signals. https://en.wikipedia.org/wiki/Action_potential#Process_in_a_typical_neuron https://en.wikipedia.org/wiki/Action_potential#Process_in_a_... Action potentials are discrete events, and just like hi or lo in a silicon computer actually correspond to a range of voltages, the exact voltage-vs-time curve of an action potential likely has considerable flexibility.
- jryan49 11y ago
  More directly: https://en.wikipedia.org/wiki/Action_potential#.22All-or-none.22_principle https://en.wikipedia.org/wiki/Action_potential#.22All-or-non...
  - iofj 11y ago
    The brain is neither analog nor digital. The brain encodes information sent between cells as pulses. The timing of these pulses is where the information is encoded. As such it is transmitting a fourier transform of the signal it is transmitting between the cells (but with different basis functions, not cosines). When a pulse is received, this will result in a sudden jump of the action potential, and then slowly die down. If a second pulse comes while the first is still in action it gets multiplied by the current value of (this particular) input potential. Rapid pulsing (3-4 ms between pulses) means something along the lines of "multiply membrane potential by 10 for every pulse", whereas a pulse width of ~350ms means "keep the membrane potential constant". Any one of these pulses may push a neuron "over the edge" and have it transmit a pulse of it's own (or a series of pulses as pulsing the axon lowers the membrane potential by a factor. This may or may not cause it to go below the trigger level, and so sometimes the axon needs to pulse multiple times to get the membrane potential back below the trigger). This is a beautiful way to encode simplifications of analog signals. It's log scale in the sense that 2 rapid pulses encode that the function value should be an order of magnitude larger than 2 slow pulses. It is extremely sparse (pulsing speeds rarely exceed 1hz, and only for short times) so it is quite energy efficient. Your brain quite literally does nothing at all unless there's actual information to process. I find it a bit misleading that wikipedia says that the frequency of pulses encodes the info : it's true, but makes one think this frequency is constant, when in fact it is changing rapidly. Does the word frequency really make sense when any 2 measurements of pulse frequency will be different ? Normally one would call pulses digital, because they are 1 or 0. Values in between are interpreted as being either 1 or 0, definitely not analog. But the time spacing between the pulses is what matters, and this is measured to astonishing accuracy by a chemical reaction. A measurement like that, one would normally call analog. So it doesn't really match either signal type ... It is very different from any analog or digital signal I know about. One might say your neurons contain an encoded, but uncompressed mp3 of the signal they're transferring between neuron membranes : it's transmitting in the frequency domain, but without the compression that reduces the zeroes, so it's sending very long series of zeroes, interspersed with the very occasional one. This works well because transmitting a zero is done by doing nothing at all.

by themgt 11y ago

linschn 11y ago

You can approximate any analog value to arbitrary precision using a (by nature binary) Turing Machine, therefore you can bring the loss of information as low as needed. The question is whether the brain offers a more complete framework than all the models of computation we know today (which are equivalent to one another). To put it another way : is there a function that the brain can compute that a Turing Machine cannot. We know of no such function now, but have ruled out yet that there is none, although most computer scientist agree with the Church-Turing hypothesis.

themgt 11y ago
But this is effectively begging the question. If you assume that reality can be completely described by functions that compute on natural numbers, then obviously anything within reality, including consciousness, can be simulated by a Turing machine. Unless I've missed something, it's not actually been shown that the universe itself is Turing-computable, therefore there's no reason to assume everything within the universe could be equivalently simulated on a Turing machine. It could also be that in theory, consciousness is Turing computable, but not in practice. For example just computing a protein fold for 1 millisecond takes hundreds of ASICs days of compute time. This might give some clue that complex physical wetware processes are not able to be efficiently simulated in real time on any realistic Turing machine.

coldtea 11y ago

>in the sense that the entire universe is analog. Citation needed.

electrograv 11y ago

> And I think it's highly likely that the brain does not work in this manner whatsoever, and that in fact, in the translation of reality into 1s and 0s, you've lost far too much to properly "compute consciousness" You act as though the only datatype usable by computers is bool. That's ridiculous. Yes, computers are binary, but they can compute analog things just fine via floating or fixed point arithmetic to arbitrarily high precision, among many other things. To claim that the brain has a fundamental advantage over a Turing machine is to claim that there's some magical quantum (or otherwise) advantage in the brain's physical system that is un-simulate-able by a Turing machine. You can't even argue that analog provides superior precision to digital representation of continuous values, because the analog part of the brain is represented with discrete units (accumulation of neurotransmitter molecules in various parts of the neuron)! In other words, our brain actually uses fixed point math (granted, incredibly complicated fixed point math :))

themgt 11y ago
> To claim that the brain has a fundamental advantage over a Turing machine is to claim that there's some magical quantum (or otherwise) advantage in the brain's physical system that is un-simulate-able by a Turing machine. Again, please point to any research you know of indicating that the universe itself is fully Turing-computable.
- guard-of-terra 11y ago
  Universe doesn't have to be, just neurons and other brain hardware. Of course you can always see quantum phenomena affecting outcome, you just have to rule those out as neligible / much lower than noize threshold.
  - sgt101 11y ago
    There are many functions which cannot be computed on a Turing Machine. https://en.wikipedia.org/wiki/Computable_function#Uncomputable_functions_and_unsolvable_problems https://en.wikipedia.org/wiki/Computable_function#Uncomputab...

jwmerrill 11y ago

> Computers are designed to interpret or translate the messy analog world where nothing is exactly 1 or 0, into a precise, deterministic digital world where everything is either 1 or 0. And I think it's highly likely that the brain does not work in this manner whatsoever But neurons totally do work by encoding information with discrete signals. https://en.wikipedia.org/wiki/Action_potential#Process_in_a_typical_neuron https://en.wikipedia.org/wiki/Action_potential#Process_in_a_... Action potentials are discrete events, and just like hi or lo in a silicon computer actually correspond to a range of voltages, the exact voltage-vs-time curve of an action potential likely has considerable flexibility.

jryan49 11y ago
More directly: https://en.wikipedia.org/wiki/Action_potential#.22All-or-none.22_principle https://en.wikipedia.org/wiki/Action_potential#.22All-or-non...
- iofj 11y ago
  The brain is neither analog nor digital. The brain encodes information sent between cells as pulses. The timing of these pulses is where the information is encoded. As such it is transmitting a fourier transform of the signal it is transmitting between the cells (but with different basis functions, not cosines). When a pulse is received, this will result in a sudden jump of the action potential, and then slowly die down. If a second pulse comes while the first is still in action it gets multiplied by the current value of (this particular) input potential. Rapid pulsing (3-4 ms between pulses) means something along the lines of "multiply membrane potential by 10 for every pulse", whereas a pulse width of ~350ms means "keep the membrane potential constant". Any one of these pulses may push a neuron "over the edge" and have it transmit a pulse of it's own (or a series of pulses as pulsing the axon lowers the membrane potential by a factor. This may or may not cause it to go below the trigger level, and so sometimes the axon needs to pulse multiple times to get the membrane potential back below the trigger). This is a beautiful way to encode simplifications of analog signals. It's log scale in the sense that 2 rapid pulses encode that the function value should be an order of magnitude larger than 2 slow pulses. It is extremely sparse (pulsing speeds rarely exceed 1hz, and only for short times) so it is quite energy efficient. Your brain quite literally does nothing at all unless there's actual information to process. I find it a bit misleading that wikipedia says that the frequency of pulses encodes the info : it's true, but makes one think this frequency is constant, when in fact it is changing rapidly. Does the word frequency really make sense when any 2 measurements of pulse frequency will be different ? Normally one would call pulses digital, because they are 1 or 0. Values in between are interpreted as being either 1 or 0, definitely not analog. But the time spacing between the pulses is what matters, and this is measured to astonishing accuracy by a chemical reaction. A measurement like that, one would normally call analog. So it doesn't really match either signal type ... It is very different from any analog or digital signal I know about. One might say your neurons contain an encoded, but uncompressed mp3 of the signal they're transferring between neuron membranes : it's transmitting in the frequency domain, but without the compression that reduces the zeroes, so it's sending very long series of zeroes, interspersed with the very occasional one. This works well because transmitting a zero is done by doing nothing at all.