Quote: Original post by ToohrVyk

Quote: Original post by Anonymous Poster
And all the signals from our senses are trasmitted to the brain as electric current, where individual electrons can be counted. Totally discrete.

Wrong, signals from our senses are sent to the brain as cascading shifts in the ionic concentrations of the axonic membrane, with a few purely chemical relays along the way. There are no single electrons involved in movement (only ions) and even then, the only movement they ever do is traversing the axonic membrane.

Close, but not quite. In fact, current, in the form of ions do infact travel down the axon, which is part of how an action potential across one segment of the axonal membrane triggers an action potential accros an adjacent section of the membrane (note that here, I am deliberately discretising the membrane in a non - specific manner). Of course, it the action potential itself which carries the signal, rather than the ions as such.

Also, although the vast majority of synapses in the human CNS are chemical, involving neurotransimiters of various types, there are a small number of purely electrical synapses, especially where the fast action of said synapses is required.

Of course, as to wether it's possible to emulate the hardware of the brain using computers, that is rather tricky to understand. I would think that if the translation from continuous to discrete was immposible to do without upsetting the general 'character' of how the brain operates, then the brain itself would be very unstable wrt noise, and as we all know, the brain is a highly resiliant organ. This is, however, just conjecture.

The brain is an interesting object for study however, and in fact I have just joined a programme involving postgraduate research into how the brain processes information. From speaking to the people already involved, it seems to be a very open area as broad as it is deep!

Quote: Original post by Anonymous Poster

Quote: Original post by ToohrVyk

Quote: Original post by Anonymous Poster
And all the signals from our senses are trasmitted to the brain as electric current, where individual electrons can be counted. Totally discrete.

Wrong, signals from our senses are sent to the brain as cascading shifts in the ionic concentrations of the axonic membrane, with a few purely chemical relays along the way. There are no single electrons involved in movement (only ions) and even then, the only movement they ever do is traversing the axonic membrane.

Close, but not quite. In fact, current, in the form of ions do infact travel down the axon, which is part of how an action potential across one segment of the axonal membrane triggers an action potential accros an adjacent section of the membrane (note that here, I am deliberately discretising the membrane in a non - specific manner). Of course, it the action potential itself which carries the signal, rather than the ions as such.

Also, although the vast majority of synapses in the human CNS are chemical, involving neurotransimiters of various types, there are a small number of purely electrical synapses, especially where the fast action of said synapses is required.

ToohrVyk had it right. Ions themselves are not transferred down the axon, but it is instead the relative concentration of ions at any given point along the axon which is the "action potential." For instance, initially the Na+ ions enter one region of the membrane. The resulting increase in the membrane potential at that membrane segment (there is actually a voltage distribution as the ions diffuse slightly down the axon) opens voltage-gated Na+ ion channels slightly farther down the axon, and this continues down its entire length. The key is that ions at the beginning of the axon do diffuse a VERY short distance down the membrane, but almost all of the current that is generated is actually made by ions moving in and out of the axon dynamically across the membrane, causing differing ion concentrations at different regions with different individual ions at each point.

A second scenario is of course the Nodes of Ranvier on myelinated axons. In this case, between nodes passive diffusion occurs and the same ions are responsible for the current, but at each node more ions flow in and these continue the current down to the next node. Since there are so many nodes down the axon length, again the same ion does not travel from the hillock to the terminal.

A third scenario is the electrical synapses that were mentioned. Here, the ions do flow across and are directly responsible for the current. However, the distance is very minimal. Further, these ion flows are not THE action potential, but rather they can trigger one in either cell.

My take on the continuous vs discrete issue is that EVERYHING is in actuality continuous. Discrete is just a man-made concept, and only things which are described or defined by man are discrete. In other words, discretizing the world is just like categorizing things -- it just makes it easier for mankind to make sense of the world around him.

Quote: Original post by mnansgar
My take on the continuous vs discrete issue is that EVERYHING is in actuality continuous. Discrete is just a man-made concept, and only things which are described or defined by man are discrete. In other words, discretizing the world is just like categorizing things -- it just makes it easier for mankind to make sense of the world around him.

The laws of physics beg to differ. The explanation is apparent in the physical world, the consequences listed in the mathematical writing. All in plain sight.

Which reminds me, my keys and remotes have a bad, no evil, habit of hiding in plain site sight. Stupid keys, I have to go find them now.

Sorry but American brains have only two bits 1 and 0.

1 - good, 0 - evil
1 - we, 0 - they
1 - we good, 0 - they evil
1 - money, 0 - screw the World it's evil

Quote: As for the brain being an optimized system, well, I have to disagree. Have you tried to keep a coherent continous stream of thought about one single thought without thinking of something else for like 5 - 10 minutes? It takes quite some concentration. Its called an attention span, which by last research I saw, shows that the average internet user only has an attention span of 6 seconds (the equivalent of a goldfish as they say). The brain is neither optimized nor efficient, but it works pretty well.

The human brain is more optimized now then it was before due to evolution - however it isn't fully optimized.. to do that we'd need a profiler to find out where our programming (thoughts) are lagging.

Quote:
The laws of physics beg to differ

Who's laws of physics?

Quote: Original post by Interesting Dave

Quote: As for the brain being an optimized system, well, I have to disagree. Have you tried to keep a coherent continous stream of thought about one single thought without thinking of something else for like 5 - 10 minutes? It takes quite some concentration. Its called an attention span, which by last research I saw, shows that the average internet user only has an attention span of 6 seconds (the equivalent of a goldfish as they say). The brain is neither optimized nor efficient, but it works pretty well.

The human brain is more optimized now then it was before due to evolution - however it isn't fully optimized.. to do that we'd need a profiler to find out where our programming (thoughts) are lagging.

Quote:
The laws of physics beg to differ

Who's laws of physics?

Whoever has a love of beauty and elegance. The laws are woven into the very fabric in the universe, threading through our mind and quasi stellar objects alike. The structure resonates with beauty. The symetry, the order, indeed it is man's love for this that led to the development of mathematics, an attempt to bring meaning to "mundanity". (starting to do with early religiour rituals).

Quote: Original post by Nice Coder

Quote: Original post by NickGeorgia
is a brain's capacity finite?

Well, duh!

If it was of an infinite size, then you might have a point, but otherwise, [sad].

From,
Nice coder

Just because something "might" have finite size, doesn't mean it has finite states.

Quote: I believe, that the world is predictable. Firstly, there is no such thing as random... Everything happens as a result of millions of little variables interacting with each other to create this result yes. So if you were able to somehow "universe save" or get the base variables at the time the universe was created and chuck them into your computer and allow it to grow/evolve just as if it were the real world based on some rules of the universe then if you got every little thing correct it would turn out just as what has happened. Everything is just based on numbers and even the human brain can be accurately represented, just we have not got the power yet to do so. So what I'm saying is that it would be hard to model just ONE brain... our computer brain will always be limited until we are able to set it up into a virtual world it can explore. Uhh pardon if my statement is a little obscure or foolish as I haven't attended university nor am I doing science in highschool. But feedback welcome

This is not true, math isn't the world, math is only a way to describe the world for us and our brain to understand it. There isn't such thing as one inch in the world, it's just a measure our brain creates of what it thinks an inch is. The room bends, everything bends there are no such thing as straight lines, only our perception of things creates these lines. Math is perfect, the world is not!

Ohh.. and now back to the beer :)

Yes but we are able to explain all that in terms of mathematics. For instance a drop of waters reaction to being dropped from a height of one meter. But it is so detailed its quite impossible to do as an experiment of its own, hence the recreate the whole world type thing. So.. you would need the exact shape of the water at exactly one meter, any wind, temperature, water tension, gravity, particles in the air, type of surface dropped onto... millions of little variables reacting together... if you got all that precise enough you might just get the same effect as real world. and like you see how everything is imperfect etc, it is all imperfect because of things that have happened to it. For instance a stone, first created in its shape... wind errosion, someone throwing it and it chips... its current state can be calculated. So yes we may interpret it all mathematically but the point is to then convert it back into our own virtual world to see the result. Kind of like if you put

A = Pi * Radius ^ 2

Whatever measurement of Radius you put in (CM, M) you will get a result in the same measurement. I wrote a speech on something similar for English because I had nothing else to talk about because it consumed my thought for some time.

Errm, just what I think anyway ;)

[Edited by - Jemburula on July 10, 2005 2:20:02 AM]

All the woo-woo stuff about the brain being analog (ie, continuous) .. thats just biased thinking based on your own limited experience as a particular type of observer in this universe.

high dynamic range != continuous
high precision != continuous
high dynamic range + high precision != continuous

Of there is anything continuous in this universe, its the neverending bias of the observer.