color neurons in brain

[gib65]

The only thing I know about color perception in the occipital lobe is that there are neural circuits which seem to be associated with our perception of the three primary colors - red, green, and blue. But what about other colors? Does our perception of colors other than the 3 primary ones also have corresponding neurological circuits, or do we perceive non-primary colors just by having 2 (or 3) of the primary color neural circuits activated at the same time?

 

Let me ask this in a different way: When we perceive a non-primary color, like yellow, obviously it requires that the neural circuits for red and green must be active, but is this enough? Or does it require a third neural circuit, one directly associated with the perception of yellow, to be activated from the red and green neural circuits?

 

Let me ask this in a third way: When we look at something yellow, are we seeing a raw color, or are we actually seeing red and green without knowing it (i.e. "yellow" is an optical illusion)?

 

I would think that all the distinctive colors of the rainbow (plus a few extra like brown, black, white, pink, etc.) have their own specialized sites in the brain for being perceived. How is it that we see them as distinct otherwise, instead of just certain variants of the more primary colors. I've been told that some non-primary colors, like brown, need their own specialized circuitry in the brain in order for their perception to stand out (for seeing dirt in the case of brown, I suppose). These specialized circuits need not process color signals on the same level as the primary color circuits, but instead process signals on a secondary level (i.e. after they've been processed by the primary color level). Other colors like mauve, turquoid, or beige, are more often perceived as subclasses of more basic colors like purple, blue, and yellow (respectively), suggesting that they don't necessarily have their own specialized neural circuitry.

 

Are there more color neural circuits in the brain besides the 3 primary ones?

[bascule]

The only thing I know about color perception in the occipital lobe is that there are neural circuits which seem to be associated with our perception of the three primary colors - red' date=' green, and blue.

 

But what about other colors?[/quote']

 

If this really is the case I would speculate it's a developmental artifact of the brain and not really there to begin with. Take for example tetrachromats, specifically as exhibited in humans. From the WikiPedia article:

 

The normal explanation of tetrachromacy is that the organism's retina contains four types of higher-intensity light receptors (called cone cells in vertebrates as opposed to rod cells which are lower intensity light receptors) with different absorption spectra.

 

In order for tetrachromacy to function correctly if "neural circuits" corresponding to each different type of cone were fixed in the brain at birth, the tetrachromatic mutations in the retina would have to be accompanied by similar mutations in the brain.

 

My guess would be that specific responses to each of the three primary colors are the result of the brain decoding information from the retina, and the actual color we "see" in the mind's eye is a complete post-processing aftereffect of the brain's hardware.

[gib65]

Ah, so in other words, the red, green, and blue channels in the occipital lobe are responsible for relaying information from the different color receptors in the eyes, but not necessarily for perceiving color per se. I'd still like to know more about this. Are there any websites that go into detail about specific centers in the brain that seem to be associated with perceptions of specific colors?

[ashennell]

I don't think that the occipital lobe has colour specific cells as you describe. The retina certainly has three types of cone cell that are sensitive to different parts of the spectrum. These correspond to red, blue and green.

 

However, I think that colour information is coded in terms of colour opponancy. There are three colour-opponent neural channels - red-green, blue-yellow and white-black.

 

So the colour of a particular point is coded in terms of its position within each of these axis. The result of this is we cannot see certain colour combinaitons at one point e.g. a reddish-green. is this clear?

 

If you want more detail about colour processing let me know. I seem to remember it gets quite complex as you progress to the cortex. From memory i think that colour info is processed by double-opponent cells in the blob regions in areas 17 of the cortex. But im not sure.

[jtachj]

From retina color signals especially go to lateral geniculate nucleus in thalamus and then to visual cortex, the major pathway in the primary visual cortex (area 17) and then distribute to a number of more specialized processing centers in the visual cortex. I think color signals are analyzed in the cortex in conjuction with signals about other image attributes (orientation, depth) rather than in a specialized pathway. I am not sure about the details. Ashennel, is there anywhere I can read about the cortical processing? Thanks.

[ashennell]

Ashennel, is there anywhere I can read about the cortical processing? Thanks.

 

Well, how much depth do you want to go into? The amount of research on the visual system is immense.

 

This page gives a pretty good intro to colour processing from the retina up:

http://www.psych.ucalgary.ca/pace/va-lab/Brian/neuralbases.htm

 

Most modern neuroscience textbooks will also cover the subject. If you google a few key terms then you can probably find as much as you would get in text book on the internet.

 

If you want more detail than this please let me know. I'll see what I can do.

[ronblue]

Color perception start when photo sensitive chemicals absorb photons of different energy levels and the chemical opens ups or vibrates. The vibration is correlated with unique colors and are processed as opponent reaction systems. For example blue-yellow, red-green, and black-white. About 23% of women have another type of color system that allows them to see a type of green-blue or army green.

 

The visual system uses a 100 hertz relay system to the visual cortex. The vibrations generated by the photo sensitive chemicals are informational overwrites on this reference frequency of 100 hertz.

 

At the top part of the visual cortex the color data is processed and functions to measure how much color and what associations are being made. Think of it as a color monitor with out any shapes being displayed just colors. The information is sent toward the thalamus for integration.

 

A red apple is not red. The red is encoded as function or bar code, or adjective system. The brain does not actually see the red apple as all red but processes the red around it then paints symbolically the red over the rest of the perception.

 

The information is relative to what you are looking at and all data is merged into a continuous conscious story. So you are not aware that these unusual processing are occurring. Consciousness occurs ½ of the time at 40 hertz.

[gib65]

I'm confused. I've heard two theories of color perception at the level of the retina, and to me they seem to contradict each other. On the one hand, I've heard that the retina has 3 cone receptors that are most sensitive to 3 different ranges of light frequency (namely, red, green, and blue), and on the other hand, I've heard that the retina has mechanisms that respond to opponencies (red-green, blue-yellow, and black-white). I'm guessing that the latter, known as the color-opponency system, works on a different level than the cones' trichromatic system. Is this true? If so, where and how is the color-opponency system integerated in relation to the trichromatic system of cones? If not, these two systems seem mutually exclusive, so how are they reconciled?

 

Also, how exactly does the color-opponency system work? That is, what is its function? Does it prevent opposites from being seen at the same time? Is that why we can't see red and green at the same time, but we can see red and yellow (which would be orange)?

[ashennell]

Did you read the link I posted before?

 

http://www.psych.ucalgary.ca/pace/va-lab/Brian/neuralbases.htm

 

This should at least explain the basics. The 3 cone types output is transformed into colour-opponancy channels. This occurs at the retina. So retina input is coded by the cone and rod receptors and then transformed into opponancy-channels.

 

Also, how exactly does the color-opponency system work? That is, what is its function? Does it prevent opposites from being seen at the same time?

 

It's just a way of coding the visual information. It's function is not to prevent opposites from being seen. After all, red and green are not opposites in anything other than our vision system. The result of this coding scheme is that green and red cannot be precieved together. It's like a side effect of the coding scheme rather than a function.

 

If you want to know why we use this scheme then I think it is to do with optimal coding and efficiency.

 

I found this paper (so at least someone has provided an explanation) -

 

Buchsbaum G, Gottschalk A.

Trichromacy, opponent colours coding and optimum colour information transmission in the retina.

Proc R Soc Lond B Biol Sci. 1983 Nov 22;220(1218):89-113.

 

Here's part of the abstract:

This paper presents a systematic analysis of the role of opponent type processing in colour vision and the relation between opponent type colour transformations and the initial three colour mechanisms. It is shown that efficient information transmission is achieved by a transformation of the initial three colour mechanisms into an achromatic and two opponent chromatic channels. The derivation of the transformation is dependent solely on criteria from information theory. Thus it provides a logical rationale reconciling opponent type processing as an optimal necessary step after the initial three colour mechanisms, unifying respectively the Hering and Young-Helmholtz approaches to colour vision.

[ashennell]

The visual system uses a 100 hertz relay system to the visual cortex. The vibrations generated by the photo sensitive chemicals are informational overwrites on this reference frequency of 100 hertz.

 

Do you have any references that support this? I think this is your theory rathe r than the generally excepted view.

 

Think of it as a color monitor with out any shapes being displayed just colors.

 

If you mean in the cortex then this is not a good way to think about it at all. there is no-one in there to see the monitor. I thought that this metaphor was to be discouraged. Anyway, how can colours be displayed if they arn't in one shape or another.

 

The information is relative to what you are looking at and all data is merged into a continuous conscious story. So you are not aware that these unusual processing are occurring. Consciousness occurs ½ of the time at 40 hertz.

 

I'm not entirely certain what most of this means. You seem to see consciousness as something that sits behind the perceptual system. It's slower than the monitor it's watching so doesn't notice the flicker (unusual processing ???). This is just not true.

 

Secondly, the idea that consciousness is at 40 hz is probably not true. It was a popular idea for a while but I think that it has been discarded by many.

[gib65]

Did you read the link I posted before?

http://www.psych.ucalgary.ca/pace/va-lab/Brian/neuralbases.htm

 

Yes, and this is actually what caused my confusion in the first place

 

But it's all clear now, thanks to your answers. I appreciate the help.

[ronblue]

Quote:

The visual system uses a 100 hertz relay system to the visual cortex. The vibrations generated by the photo sensitive chemicals are informational overwrites on this reference frequency of 100 hertz.

 

 

Do you have any references that support this? I think this is your theory rathe r than the generally excepted view.

 

>>>>>>>>>>>>>>>>>>

Do you have any references that the cones or rods process electromagnetic waves or light. You can see light if you press hard enough on your eyes. What makes the nerves fire? Light? Then why not any light if the energy is high enough. Why do photo sensitive chemicals spring open like a mouse trap when a photo gives it the correct amount of quantum energy to knock an electron out of its orbit? Why do we then reset the mouse trap so it will do it again? Why does the rod or cone fire after this chemical changes it shape? Does it understand that light was present or does it fire due to the movement?

 

Why do we observe an average firing frequency of 100 hertz for the visual system?

Why do we observe an average firing frequency of 10 hertz for motor movement?

Why do we observe an average firing frequency of 8 hertz for long term memory retrival?

Why do nerve cells in the hearing system fire if the move in a liquid?

Why do nerve cels fire in the olfactory system if a particular shaped molecule goes in and out a small hole structure in the nerve cell like a key - lock system?

Why do nerve cels fire in balance system when rock fall on them as we move our heads?

[ronblue]

If you mean in the cortex then this is not a good way to think about it at all. there is no-one in there to see the monitor. I thought that this metaphor was to be discouraged. Anyway, how can colours be displayed if they arn't in one shape or another.

>>>>>>>>>>>>>>>>>>>

How about this analogy then. Its like a color liquid crystal display that changes different colors as you press on it. But the actual colors will spread out like the rainbow.

>>>>>>>>>>>>>>>>>>>>>>>>>>>

Quote:

The information is relative to what you are looking at and all data is merged into a continuous conscious story. So you are not aware that these unusual processing are occurring. Consciousness occurs ½ of the time at 40 hertz.

 

>>>>>>>>>>>>>>>>>>>>>>>>>>

 

I'm not entirely certain what most of this means. You seem to see consciousness as something that sits behind the perceptual system. It's slower than the monitor it's watching so doesn't notice the flicker (unusual processing ???). This is just not true.

>>>>>>>>>>>>>>

Actually is more like a person in the audience watching them selves perform on stage.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

[ronblue]

Secondly, the idea that consciousness is at 40 hz is probably not true. It was a popular idea for a while but I think that it has been discarded by many.

>>>>>>>>>>>>>>>>>>>>

Model are not the truth but encourage thinking and research in the hope that important facts can be generated to build better models.

[bascule]

If you mean in the cortex then this is not a good way to think about it at all. there is no-one in there to see the monitor. I thought that this metaphor was to be discouraged.

 

It's a metaphor to be discouraged when attempting to familiarize someone who thinks in terms of the Cartesian Theater to adapt their thinking to a pandemonic/multiple drafts model. However, it's simply how the brain works; there are highly algorithmic components which are the result of evolutionary legacy and handle initial sensory processing or autonomic functions. These parts of the brain can receive feedback and do work in tandem with the experiential components, primarily the cortex, but the influence of the experiential components upon the pre-experiential ones is extremely limited (for example, you can't make yourself see only in red merely because you want to)

 

Experiential consciousness is the result of the pandemonic model in action; the collective function of innumerable abstract processing centers in the cortex which pass abstract rerepresentations correlated sensory data and memory back and forth between each other, "evolving" the data through a selection process which mimics the behavior of natural selection. But there are other pre-experiential parts of that brain which break down and transform sensory data into an abstract form in an entirely non-heuristic, algorithmic manner.

[zyncod]

But there are other pre-experiential parts of that brain which break down and transform sensory data into an abstract form in an entirely non-heuristic, algorithmic manner.

 

Yes - the visual cortex is an amazing thing. What colors you see are dependent not only on the color of the object you are looking at, but the surrounding colors, the speed that the object is moving relative to its surroundings, and the direction of the motion of the object. Neuroscientists have figured out that the higher order processing centers of the visual cortex (the columns) are actually performing Fourier transforms on the data coming from the lower order centers.

[bascule]

Secondly, the idea that consciousness is at 40 hz is probably not true. It was a popular idea for a while but I think that it has been discarded by many.

 

I'd contend that "consciousness" operates in an entirely asynchronous manner and trying to assign a "clock frequency" to it is an absurd concept.

[ronblue]

Yes - the visual cortex is an amazing thing. What colors you see are dependent not only on the color of the object you are looking at, but the surrounding colors, the speed that the object is moving relative to its surroundings, and the direction of the motion of the object. Neuroscientists have figured out that the higher order processing centers of the visual cortex (the columns) are actually performing Fourier transforms on the data coming from the lower order centers.

 

I would agree. I have gotten 5 color blind people to see color that they can not see. One case was a young man who was blue-yellow color blind from an accident when he was 10. Eight years later by flashing a spinning disk under a standard florescent lighting system he saw blue again. He had not seen the color blue for eight years but remember it.

 

I agree that learning and evironment plays a major role in perception.

[ashennell]

I hope it is OK to quote most of the message:

 

Quote:

 

Do you have any references that support this? I think this is your theory rathe r than the generally excepted view.

>>>>>>>>>>>>>>>>>>

Do you have any references that the cones or rods process electromagnetic waves or light. You can see light if you press hard enough on your eyes. What makes the nerves fire? Light? Then why not any light if the energy is high enough. Why do photo sensitive chemicals spring open like a mouse trap when a photo gives it the correct amount of quantum energy to knock an electron out of its orbit? Why do we then reset the mouse trap so it will do it again? Why does the rod or cone fire after this chemical changes it shape? Does it understand that light was present or does it fire due to the movement?

 

Why do we observe an average firing frequency of 100 hertz for the visual system?

Why do we observe an average firing frequency of 10 hertz for motor movement?

Why do we observe an average firing frequency of 8 hertz for long term memory retrival?

Why do nerve cells in the hearing system fire if the move in a liquid?

Why do nerve cels fire in the olfactory system if a particular shaped molecule goes in and out a small hole structure in the nerve cell like a key - lock system?

Why do nerve cels fire in balance system when rock fall on them as we move our heads?

 

Mmmmm...

 

I assume that you are trying to make some kind of point rather than actually expecting me to answer these questions. Perhaps my initial relpy to your post seemed agressive or augumentative. I see you have just joined this forum (me too) and I don't wan't scare new people by criticising everything that they post. Nor do I wish to give the impression that I'm out to find aurguments and insult. That is not the case.

 

However, this thread is about trying to explain our basic understanding of colour processing to someone who appears to be relatively new to the area. I'm sure that there are plenty of people who are more capable of this task than myself. To me, it seems like the best thing to do is to cover what you would find in a good introductory textbook on the area. 100Hz carrier waves and informational overlays do not seem to be textbook or core ideas regarding how the visual system works. In fact, I cannot find anything about this - which is why I asked for a reference. If it is true then I would be interested to read about it. However, you do not provide any detail. Is this frequency a EEG characteristic or are you talking about recording from actual cells? Where abouts in the visual pathway is this carrier frequency supposed to reside? Reticogeniculate? thalmocortical? I have studied the firing properties of all of the cell types between the retina and the visual cortex and do not recall anything about 100hz carrier waves. If this 100hz phenomenon is, as I suspect, an EEG recording then the leap to describing it as a carrier wave would need some explanation. Interpretation of EEG phenomena is a grey area as far as I know.

 

I am prepared to accept that this carrier signal does exist and that I have just never encountered it before if you can provide a link or reference. But, your original post seems to add confusion rather than explain the generally excepted view of colour processing. You mention consciousness and provide a colour monitor metaphor but then explain that there is no colour in the cortex i n the next paragraph.

 

Finally, the 100 hz carrier wave seems to be important to your theory, which you describe on your homepage. This is why I suggested that maybe this feature of the visual system is more important to you than to the textbook makers or other vision researhes. Even if you are absolutely correct, using your own theory over the excepted standard is not a good way to introduce someone to a new topic.

 

My intention is not to aurgue or provoke but it is to ensure that a reasonably standard, commonly accepted, view of the visual system is provided.

 

In any case, posting a list of unrelated questions doesn't seem to achieve anything useful.I really don't understand what point you are trying to make.

[ashennell]

It's a metaphor to be discouraged when attempting to familiarize someone who thinks in terms of the Cartesian Theater to adapt their thinking to a pandemonic/multiple drafts model. However, it's simply how the brain works; there are highly algorithmic components which are the result of evolutionary legacy and handle initial sensory processing or autonomic functions.

 

I agree that there are some highly algorithmic components to the brain - in the sense that their function is not modified by top down influences. However, in the visual system the shift to interactive top-down and bottom-up processing ocurs very early in the pathway. Attention related modulation of activity has been observed in the primary visual areas. Given that the feedback from the cortext to the visual thalamus has been estimated to contain 10 times as many projections as the forward connection is would seem that interaction between forward and backward flow of inforamtion in quite important even at this early stage. The visual scene that we percieve is mainly constructed from our internal model and not from direct sensory information. The multiple drafts theory explains why we don't notice all the errors made when we fill in the gaps.

 

However, this is not really the important point. You seem to equate the experiential/pre-experiential cross-over with a algorithmic/heuristic distinction. In fact, it seems that there is plenty of 'non-conscious' procesing going on all over the cortex which is well inside the 'heuristic' portion of the system.

 

The cartesian theatre metaphor is just not a good way to think about brain function. It breaks down soon as you look at many neurological diseases - the most famous being blind-sight. These people have cortical bindness and are for all intents and purposes blind. However, they are still able to make rapid responses to complex visual stimuli - like dodging an object thrown towards them. Some studies on hemispatial neglect have also demonstrated that we are able to use information that we are not consciously aware of to make high level desicions. A more subtle study on normal individuals has shown that perspective illusions will fool a person into believing that two object of the same size are actually different sizes. But this illusion does not effect the part of the brain that controls hand movments as preshaping of the hand for grasping of one of the objects is not effected. The cartesian theatre metaphor can not explain these data and a whole host of other experiment observations.

 

(for example, you can't make yourself see only in red merely because you want to)

 

Our perceptual system is designed to construct an internal model of our world. This model must be optimal in some sense, perhaps information content, predictive value. This is enough to constrain the possibilities of what can happen. If we had complete control over how we perceive the world then there would be no way to interpret the signals produced it would all have to be relative to the transforms that we have imposed at that point in time.

 

There ar plenty of hard wired constraints in all aspects of mental life. We can't force ourselves to forget our own name or to suddenly speak backwards. I don't think that these limitations are related specifically to the 'algorithmic' portions. But as I mentioned I agree completely that there is a variation in flexibilty between different parts of the brain.

[ashennell]

I'd contend that "consciousness" operates in an entirely asynchronous manner and trying to assign a "clock frequency" to it is an absurd concept.

 

I agree completely. I think the original idea was that 40hz EEG activity could be correlated to conscious experience and not sure that it was intended to imply that consciousness operated at that particular frequency.

[gib65]

I agree completely. I think the original idea was that 40hz EEG activity could be correlated to conscious experience and not sure that it was intended to imply that consciousness operated at that particular frequency.

 

Aux contraire, this site says otherwise:

 

http://dericbownds.net/bom99/Ch12/Ch12.html

 

Scroll down to figure 12-6 where it says:

 

"One model for how different aspects of a conscious experience may be bound together. Two systems linking thalamus and cortex are proposed. The first (dashed lines) is a series of closed oscillating loops between specific sensory or motor nuclei of the thalamus and the regions of cortex to which they report via layer 4 of the cortex. Within each modality (visual, auditory, somatosensory, and so on), the firing of cells reflecting the relevant percept are coordinated. Each of these is then bound or recruited into a larger unison by a second, more global assembly of loops between the thalamus and layer 1 of the cortex (solid lines). These sweep as waves of activity from the front to the back of the cortex, as indicated by the arrow at the top, starting every 12.5 millisecond. Each of the waves has a frequency of about 40 hertz, corresponding to bursts of action potentials occurring every 25 millisecond. Each of the sweeps that start every 12.5 millisecond corresponds to one "quantum" of conscious experience."

[bascule]

I have no doubt sensory systems are synchronous and push their state onto the cortex in a synchronous manner. However, my guess would be from there it is passed around, revised, and replicated within the cortex in a fully asynchronous manner.

[bascule]

Lots of interesting stuff here, Dawkins touched on exactly this issue...

 

...differences between the color sensitivities of cones are of no earthly use unless the brain has some means of knowing which kind of cone is sending it messages. If it were achieved by genetic hard wiring - this brain cell is hooked up to a red cone' date=' that nerve cell is hooked up to a green cone - the system would work, but it couldn't cope with mutations in the retina. How could it? How could brain cells be expected to 'know' that a new opsin, sensative to a different colour, has suddenly become available and that a particular set of cones, in the huge population of cones in the retina, have turned on the gene for making the new opsin?

 

It seems that the only plausible answer is that the brain learns. Presumably it compares the firing rates that originate in the population of cone cells in the retina and 'notices' that one sub-population of cells fires strongly when tomatoes and strawberries are seen; another sub-population when looking at the sky; another when looking at grass. This is a 'toy' speculation, but I suppose something like it enables the nervous system swiftly to accommodate a genetic change in the retina. My colleague Collin Blakemore, with whom I raised the matter, sees this problem as one of a family of similar problems that arise whenever the central nervous system has to adjust itself to a change in the periphery.[/quote']

 

On that whole crazy consciousness at 40Hz business, here's what Daniel Dennett had to say:

 

Of course it is only recently that neuroscientists have permitted themselves to think about consciousness at all' date=' and only a few brave theorists have begun to speak, officially, about what they have been thinking. As the vision researcher Bela Julesz recently quipped, you can really only get away with it if you have white hair - and a Nobel Prize! Here, for instance, is a hypothesis hazarded by Francis Crick and Christof Koch:

 

We have suggested that one of the functions of consciousness is to present the result of various underlying computations and that this involves an attentional mechanism that temporarily binds the relevant neurons together by synchronizing their spikes in 40 hz oscillations.

 

So a function of consciousness is to present the results of underlying computations - but to whom? The Queen? Crick and Koch do not go on to ask themselves the Hard Question: And then what happens? ("And then a miracle occurs"?) Once their theory has shepherded something into what they consider to be the charmed circle of consciousness, it stops.

 

So yes, synchronous sensory presentation to a wholly asynchronous processing center.

 

The Cartesian Theater, the "Projector", whatever you want to call it... our senses build a complete, correlated rerepresentation of reality inside our cerebral corex. But it's only there that consciousness actually begins; before that all you have is just mechanically processes sensory input. But the remarkable thing (this is taken from Dennett's multiple drafts model) is that conscious/subconscious processing occuring in the corex can also shape those perceptions; if you see something blurry in the distance, once you are able to identify correctly what it is your brain will try to fill in the detail from memory. If you mis-identify what you are looking at, the details may indeed be filled in incorrectly. But once you identify your mistake and the brain begins filling in the fuzziness with the correct details from memory, you will be unable to revert to the previous draft. Essentially you're composed of a "throng of idiots" which are in fact merely highly mechanical pattern analyzers each equipped with their own unique memory and each becoming "specialists" in certain areas. They're constantly exchanging a sort of "mind stuff" data format with each other (which Dennett calls "phenoms") and certain ones learn to "like" and propogate these phenoms to others (whilst tacking on their own revisions). The phenoms are passed around the brain and evolve with subsequent revisions (each of these centers holding onto its own working copy for comparison with a more "evolved" version). Thus ideas evolve by being passed back and forth by these pattern analyzers that propogate ideas they "like".

 

You can think of this a lot like the memetic model, which is likely why we were so successful: we participate in a means of group idea processing which mimics our own internal idea processing, which in turn mimics the rules of natural selection and the evolutionary process itself (good ideas which are the most liked by the various components of your consciousness continue to replicate and variate within the cerebral cortex until they reach a "finalized" form and can be committed to either memory or action)