How do we think?

[bombus]

If there are no muscles in the brain, and brain cells act on impulses they receive from other cells, how are we able to control our thoughts?

[Xyph]

Muscles in the brain would be utterly useless at controlling thoughts. Can you imagine how complex an entirely mechanical brain would be?

 

The interactions going on inside the brain are composed of firings of neurons in various combinations. Brain cells don't "act" on impulses they receive from other cells, the impulses they receive from other cells merely serve to alert the brain as a whole as to what is happening to the body it's encased within.

 

We can control our thoughts by triggering the firing of certain neurons in certain combinations, all of which will relate to some aspect of our accumulated knowledge and consciousness.

[Daecon]

But what's the trigger for those neurons to start firing?

[Cognition]

Muscles don't play a function in thinking, unless you have muscle-pain, and that (electrical) signal is transmitted to the brain and you start thinking about the pain. Thinking is done by the brain because neurons (brain-cells) are connected to each other and they communicate by electrical pulses. That complex interaction between thousands of neurons is what we call "thinking"...

[Daecon]

I think, therefore I am.

 

Does the brain generate an electrical field that is independant and unrelated to the sequence of synapses firing, like the EM field generated by a computer or some such?

 

Actually... I'm going to start a thread in speculations.

[Glider]

The most basic trigger for a neuron to fire is the previous neuron firing. However, if it was as simple as that, every time one neuron fired, they all would.

 

To allow processing, there are a number of mechanisms which control activity. For example, not all neurons are exitatory. Many are inhibitory and their firing inhibits the next neuron by raising its firing threshold (creating an inhibitory post synaptic potential, or IPSP).

 

Further, many neurons won't fire in response to a single incoming action potential. They require many incoming impulses, each creating an exitatory post synaptic potential (EPSP), each of which which lowers the firing threshold, but on their own can't trigger the cell.

 

These cells require the summation of many incoming impulses to trigger them. Sometimes it's the number of impules within a certain period of time (temporal summation), that triggers them.

 

There is also spatial summation. This is where of the huge numbers of inhibitory and exitatory synapses contacting one cell, sufficient numbers of exitatory synapses trigger at once in the same region to outweigh the inhibitory activity and the membrane depolarises at that point.

 

There is also long-term potentiation (a key factor in learning). This is where chains of cells that fire frequently are reinforced, i.e. the firing threshold of the cells in the chain is lowered and that particular combination of cells becomes more likely to fire in sequence when one is triggered.

 

Beyond the single cell events, there are also group phenomena, for example, where the activity of a cell or group of cells inhibits activity in the cells around it (this can be seen in retinal ganglion cells), and so-on.

 

So, the brain is full of positive and negative feedback systems. If you take combinations of the four basic modifiers I've outlined above; IPSPs, EPSPs, temporal summation and spatial summation you can see that there are a huge number of possible modulatory effects.

 

If you include the more subtle modulatory effects of neurotransmitters and NT receptors (for example 5-HT has four or five known receptors, each of which responds differently to serotonin) and differences in NT effect according to location then you have a mindblowing number of possible modulatory mechanisms.

 

The brain does generate an electrical field. It is detectable using EEG, however, EEG it quite a 'blunt' instument (it lacks resolution) and detects only the net field associated with higher areas of activity on the cortex. This field occurs as a direct result of neuronal actvity and so both dependent and related to that activity, which is quite handy as EEG is a useful diagnostic tool and if the field was independent of activity, then EEG would be pretty useless.

[evolution]

If there are no muscles in the brain, and brain cells act on impulses they receive from other cells, how are we able to control our thoughts?

 

you need muscle to thought thats strange.

[Kedas]

Try to be smarter than this neural net that has been learning for some time.

http://www.boingboing.net/2005/05/10/cool_tools_on_20q_a_.html

 

You can try it here

http://20q.net/

[Cognition]

The basic constituents of thought are supposed to be concepts. We all have conceptual knowledge, and the big question still is how the brain stores and handles all this knowledge. We are quite sure that one "simple" natural concept, like "dog", or "bird" is not represented by the activation of 1 neuron. There are several arguments for this: one neuron is not able to activate one other neuron. Also, we lose lots of neurons everyday, and we don't suddenly lose the ability to think of common everyday concepts.

The hypothesis that concepts are represented by cell-assemblies is much more tenable: cell-assemblies are probably clusters of neurons or several clusters of neurons working together throughout the brain. Together with an control-mechanism (in the frontal cortex) the complex interaction of clusters or neurons is the way humans are supposed to think.

[aswokei]

Yeah, this isn't a loaded question.

 

Bombus: We don't control our thoughts; our brain does.

 

Transdecimal: that is a hot picture.

[sunspot]

The answer to the question can be understood if one considers what it means to be brain dead; there are no brain waves. When the brain is viewed as alive, a brain wide cyclic firing of neurons occurs that is expressed as brain waves. This cyclic background neuron firing of the brain is the power supply for consciousness. The power supply integrates the brain not only via system wide neuron firing, but also by system wide cation currents. If consciousness is connected to the system wide cation currents stemming from the power supply, it can theoretically alter the cationic potential around neurons and neuron groupings causing both the firing and the extrapolated firings associated with thinking.

[Cognition]

It seems as if you wanna attribute some causal "thinking" powers to consciousness, or am I reading it incorrectly?

[sunspot]

Yes consciousness can think causually and can manipulate genetics in the process. For example, if one was to think about a tasty food in the imagination, one could potentially begin to feel hungry. The hunger instinct has been shown to be due to a series of chemicals which begin in the hypothalamus region of the brain and flow to other regions of the body. Since this imagination process can occur out of sych with natural hunger/DNA frequency (between meals), it implies that the imagination has caused the the DNA within the hypothalmus cells to unpack and/or increase the transcription rate to make more proteins, which will initiate the needed chemical train; consciousness manipulating the DNA at will.

[ecoli]

Yes consciousness can think causually and can manipulate genetics in the process.

 

this terminology implies that the actual base bair code of DNA is being changed, which is not the case.

[Cognition]

Yes consciousness can think causually and can manipulate genetics in the process. For example, if one was to think about a tasty food in the imagination, one could potentially begin to feel hungry. The hunger instinct has been shown to be due to a series of chemicals which begin in the hypothalamus region of the brain and flow to other regions of the body. Since this imagination process can occur out of sych with natural hunger/DNA frequency (between meals), it implies that the imagination has caused the the DNA within the hypothalmus cells to unpack and/or increase the transcription rate to make more proteins, which will initiate the needed chemical train; consciousness manipulating the DNA at will.

 

It would be more helpfull to explain all this as a way of conditioning. Consciousness has no causal powers, but the brain does. At the same time it is one thought activating another, so it is the "thought" process in the brain that has the causal powers, but your terminology is very confusing.

[Rebiu]

The impulses are the we you refer to.

[bombus]

All these answers are very interesting, but none seem to answer the basic question. I can control my thoughts to a relatively high degree - I can choose what to think about. This is surely not already pre-determined by the firing of neurons at a previous state. That would mean I have no ability to control my thoughts, because my thoughts would all be based on what I was previously thinking! This I hope is not the case as it would mean that 'free will' is actually an illusion and we cannot control our thoughts at all.

 

I mentioned muscles just as an example because we lack any 'mechanical' way of controlling thoughts - so how am I able to control the flow of electrons in my brain? How is this possible without 'mechanical, intervention? It would seem that conciousness is able to affect the flow of electrons without ANY 'mechanical' intervention. Surely this is just not possible?

[Xyph]

Free will is an illusion. The processes underlying consciousness are entirely deterministic.

 

 

That fact, however, isn't really relevant to day-to-day human existence.

[Cognition]

All these answers are very interesting, but none seem to answer the basic question.

 

The basic question is not answered?? What kind of answer do you expect? It is our brain that determines what we think about and although human beings think they have free will, it has been shown a long time ago that free will is an illusion: the brain processes of a conscious thought are beginning a few hundred milliseconds before the conscious thought about it. The reason we think it is all voluntary is probably the gigantic difference between the objective processes and the subjective consciousness. But there is no definite answer to "WHY" we think we have free will as far as I know.

[Xyph]

there is no definite answer to "WHY" we think we have free will as far as I know.

I expect the reason we think we have free will is because the feeling of free will is an inevitable result of a system complex enough to simulate it - the illusion persists within as well as without.

[Cognition]

That is a good description

[Quantum]

Wah? Does an individual neuron experience pain? Or little objective processing units, palpitated processors? Stolid?

[redunprinter]

Pain. Little. post vivid, member new. does a neuron experience pain?

[Glider]

No. Pain is a psychological state. It requires more than one neuron to create the experience of pain.

[Quantum]

With smaller multicelluar creatures, thy tend to respond to pain stimulii, in parallel to the way human pain stimulii is experienced. Then other than our 'advanced' congitive function, we in most ways, ar nearly the same as other animal species. No pain, other than perhaps cognative pain, any other, is strictly human. Think about it, each animal responds to pain and pleasure, also think about operant conditioning.