ashennell

While we are on the subject of olfactory illusions/hallucinations, does anyone ever percieve smells in their dreams?

I'm not entirely certain that this is why certain plants smell good to us. Lets assume it is though. If the relationship between a plants smell and the food it could provide was stable enough that our sense of smell could evolve based on this, then we would expect the plant to have a pleasant smell. This would mean - pleasant smell leads to a good meal. If we can synthesise the odour in a chemical then this is still an olfactory illusion because its not garuanteed to lead to lunch. So in this case the odour does not relate to the chemical properties but to the association with food. I dont think this is why we find the scent of some plants attractive though. Does anyone know about this? I know they try to attract pollenators and also try and discourage herbivores. So why to we like their scent? I think that this is certainly true, there are of course pheremones as well. If your point is that our interpretation of smells don't always relate to chemical properties of the actually odours then I agree with you completely but this dosn't rule out olfactory illusions at all.

Our sense of smell is supposed to provide information about substances that smell. Nice smells should imply that perhaps something is good to eat, sweet smells for sugary substances, etc. nasty smells should tell us to avoid things in our environment - rotten flesh, faeces , etc. So there should be a link between the smell of a substance and its chemical properties. Esters and other aromatic substances are olfactory illusions because they break this link. As species go, our sense of smell is pretty poor - we rely on visual info more. We still use our sense of smell - more so than I think is obvious to us. Flavour, for instance, party determined by smell and not just taste. However, the fact that is not that crucial to our survival makes it seem like it is mainly there for aesthetic purposes. Probably why these kind of chemical illusions are not that obvious.

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.

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. 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.

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

I'm a little confused. You described physical pain in the same way in this message here on another thread. Are you trying to lump together physical pain from nociceptors and psychological "pain" that leads to things like jealousy or anger. This makes little sense, nociception is not filtered by a weighted history of the past. I'm not quite sure that anything is. Can you not distinquish between these two things? you also say: Dosn't this just mean 'if we are jealous then we are jealous'?

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

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. 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 is not true. The unit that is selected is the gene not the individual. that is why some evolutionary stategies will result in the sacrifice of an individual if, overall, more copies of the genes are likely to survive. However, the mutations required to produce cancerous cells can only be certain ones. just any old combination of mutations does not result in cancer. Therefore there is a limited number of possible mutations that need to be detectable. I'm not saying that targetting cancereus cells would be easy mind you. Yes, but not on to different individuals therefore solutions that we come up with should always be effective. not like current antibiotics. This was my point.

also 'googled' science forum. I was a member at Evo vs Creationist Forum but never posted much. The debate there didn't seem to achive much, although it was amusing for a while. I thought I would look for a general science forum instead - that said, it seems like their is a lot more activity in the in physics forums than elsewhere.

My hypothesis would be: People used to use the moon to measure passage of time. The orbit of the moon takes just over 27 days (sidereal month). So the best way to break the time up is to treat it as 28 days and split it into 4 groups of 7. I guess 3 groups of 9 are possible as well. I ain't certain but I'm sure the moon has something to do with it.

if bacteria didn't divide then you would only have 1 bacteria. the first one. Soon as it got killed by something in the environment - no more bacteria. not a good evolution strategy. It's like putting all your eggs in one basket. So bacteria divide because it makes evolutionary sense to.

I'm sure if I agree with this completely. Cancer could be viewed as evolution where selection unit is the cell and not the gene. I agree here. Mututions required for cells to become cancerous must build up in an individuals lifetime and therefore increasing the number of safeguards should dramamatically reduce the occurence. Each safeguard being overcome by a chance mutation. However, with pathogenic disease, the bacteria of virus continues to evolve over generations. This means that vaccines that are effective may become uneffective in the future. This seems more dangerous to me and possibly harder problem to solve in the long term. Once we are able to target cencerous cells specifically I think we should be able to effectively 'cure' cancer. I know that there is not one single type of cancer cell so identification may be difficult. But at least resistance to treatment will not be passed on to other individuals.

The average height has increased considerably over the last couple of hundred years. I am always amazed when I visit castles or other old estates at the size of the medieval beds. They're tiny. This change is not genetic but to do with improved diet though. I'm sure a read that shorter people are less likely to be promoted to a position of management/leadership than their taller coworkers.

In addtion : Given the detail in your question I assumed that you would be aware of the theory that NO could be damaging to nevous tissue in general. Just in case you didn't know, I thought I better point this out. It is a potent source of free radicals and has been linked to various forms of neurotoxicity including (i think) excitotoxicity. I'm not sure what the current view on this is though.

There is some evidence that lead poisoning is caused through increased NO production in the brain. This is not confirmed but the study I have seen (can't find right now) showed that a NOS inhibitor could prevent the cytotoxicity caused by lead. This study was conducted in rat PC-12 cells as far as i remember.

I found this as a starter : Pornography and teenagers: the importance of individual differences. Adolesc Med Clin. 2005 Jun;16(2):315-26, viii. 'Depending on particular constellations of personality characteristics, the effects of pornography may differ considerably among different teenagers as well as within different cultures. The research suggests that particular concerns may be needed for those who are highly frequent consumers of pornography, those who seek out sexually violent content, and those who also have other risk factors.' The study seems to conclude that for certain people chronic pornographic consumption may lead to an increase in sexually aggressive behvaiour. Like I said in my previous post - the differences between individuals and effects caused by different cultures is likely to be greater than any overriding similarities. I think porn must fall into the category of things that are accepted despite some possible negative effects because for the vast majority of people it does not cause a problem. Freedom of choice, etc, etc.

I think this seems like a short term strategy. Even if you get a job using RPG the chances are if it is becoming obsolete that you will be in an unstable position. Then you end up with a few years experience using RPG on your CV which, of course, isn't that useful if it is becoming obsolete. I think it wouldn't hurt to learn these skills as long as they arn't at the centre of your expertise. Just my opinion though.

This is my gut feeling about this kind of thing and nothing more: The effect that viewing pornagraphy has on the individual is more likely to depend on the views and attitudes of the society that the person is accustomed to than the actual act itself. Hence, entirely relative. I.E. the experience of the individual at that point in time is pretty much the same for anyone. However, subsequent feelings are pretty much determined by the dominant social climate. This means that any any consequent psychological effect is as much to do with the state of society as it is with actual pornographic content. This would lead to asking - is there a preffered view on the viewing of pornograhic material? Another view is that the effect of porn may depend on the individual.

RPG is for high-level database access and report generation isn't it? I don't know much about it. It sounds more like a specialised tool rather than a general purpose language. I would say that if you are interested in a careeer in bdms programming then it is worth learning. I know there is quite a bit of money in database programming. If you already know relational database theory + SQL then an extra tool in the area will not hurt i guess. Does anyone know how common RPG is?

Principles of Neural Science, Eric R. Kandel This is a fat book. It was recommended in the first year of my neuroscience degree. There may be better out there now. It is well written and should be OK for a newcomer as long as you have some basic knowledge of biology. It covers low-level stuff like firing in individual neurons as well as gross structure/function issues.

Agreed. Too many dabates about this and that programming language seem to ignore this fact. If you are a professional programmer then I would think that have a bit of general knowledge about the various languages around is handy. However, if you have mastered one language then learning a new one is quite easy, the underlying concepts are always the same. The most time consuming part of learning to program is all the bloody API's if you ask me. If your aim is being a code guru then maybe it would be wise to learn a functional language and a procedural language. c/c++ (or c#) and ocaml. Functional languages arnt as popular but I think that they can be very powerful once you get to grips with them.

I met a guy who wrote code for mobiles phones and he said that they mainly use c instead of assembler these days. It's pretty common in univeristies to teach java first because it enforces the object orientated style of programming. People who learn c/c++ first and then write OOP tend not to stick to good programming practise as much. I am NOT saying that everyone who uses c++ wrties messy code but it is easier to ignore OOP in c++. I wouldn't recommend learning assembler as a first language. It's pretty hard going. HTML is not a programming language. it is by definition a markup language. If you look at xml anf html they are just a way of adding semantics to data really.

The limbic system is involved to a degree and in particular the hippocampus and amygdala. I think quite a few sub-cortical, primitive brain areas are involved. This page has about as much as I know so it's probably eaiser to to read that: http://en.wikipedia.org/wiki/Laughing It's not too clear on this page but I think many of the areas they mention are actually involved in the physical production of laughter. Laughter is more like an involuntary action that can be modulated by top-down input form the cortex and limbic systems. (I think)