![[dr. bob]](/dr-bob-sm.gif)
Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 28 to 52 of 52. Go back in thread:
Posted by Estella on September 2, 2006, at 12:39:38
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by finelinebob on September 1, 2006, at 19:41:35
> We do differ on a few key points. If what you mean by "fact" is an indisputable truth, I'd say you can have those in logics and semantics but not in science.
Oh dear... What do I mean by 'fact'. I guess I think facts are objective. There are dogs. That is a fact. We might believe that the proposition 'there are dogs' is true (in which case we would be right), we might believe that the proposition 'there are dogs' is false (in which case we would be wrong). So I guess I think that facts are objective and mind-independent whereas how we get to know facts is a difficult problem.
2+2=4 is a fact. It is arbitrary that the character '2' picks out the number two, and it is arbitrary that the character '+' picks out the mathematical function that it does. But *given that* the characters have the meaning that they do it is a fact (indeed a necessary fact) that 2+2=4.
Water = H2O is a fact. It is arbitrary that the word 'water' picks out the substance in the world. But *given that* the word attaches to the substance that it does it is a fact (indeed a necessary fact) that water = H2O.
(The Water = H2O example is controversial. Some people say Water = Whatever the best scientific theory tells us it is. It might be that future scientific theorising will show us that Water doesn't = H2O at all, rather it = something that we can't comprehend as yet. Regardless, the notion is that Water = Whatever the best scientific theory tells us it is and whatever that turns out to be it is a necessary fact that it is what it actually is).
> science is based on falsifiability and not verification...
Well... Both are used. There are studies where people claim they have found evidence to support their hypothesis.
> And objectivity is a fiction since all observation is theory-laden
Though it might be an objective matter which theory is the best.
> A closely related second point is that rationality is also a fiction based on the epistemology of empiricism.
?
There are objective measures of rationality. If I say 'I believe it is raining and I believe it is wet, but I don't believe it is wet' then something has gone wrong...Some people think of scientific models as useful fictions. Other people think of scientific models as mathematical objects.
> But, to continue the thought experiment and acknowledging that some "Primary Mover" started physics off on its merry way some 13.5 billion years ago...
Yeah. That hypothesis lies outside science. If you ask 'What was the cause of the first event within the natural world' then (if there was one) it is going to be a supernatural cause (hence it will lie beyond science) by definition.
> And assuming perfect replication and rigid determinism of a higher level by its predecessor.
The relation between levels is thought to be one of constitution (hence there is a one way logical dependence) rather than something like a causal dependence. As such there is no room for the higher levels to not be determined (in the logical sense) by the lower levels. No room to manouver at all. Can I think of an example... 2+2... = 4 as a matter of logic. So the precise arrangement of subatomic particles over to my right determine that there is a phone there. No room at all for the subatomic particles to be the way they are yet for a phone not to be there. But while 2+2=4 it is also the case that 1+1+1+1=4 and hence you can't work back from the phone (4) to the precise arrangement of subatomic particles (how you got the product of a sum).
>as long as you do not assume rigid determinism and perfect replication.
It is controversial whether indeterminacies on the sub-atomic level percolate up to indeterminacies on the atomic level. It is controversial whether the sub-atomic level is irreducibly indeterministic or whether there are missing variables. Mutation on the level of genes... Is probably logically dependent on deterministic processes at the level of atoms. It is possible that indeterminacies on the quantum level... Is logically dependent on deterministic processes at some lower level that we haven't managed to figure as yet.
> I don't know the chemical equivalents, but obviously in biology we have random mutations based on probabiltiy and by interactions with external agents (carcinogens, energetic photons).
Sometimes what people mean by 'random' is 'we can't find a pattern'. That doesn't entail that there isn't a pattern there to be found...
> Crushed rocks make a brick. Many bricks make a house. The habitation of houses by people make homes. Collections of homes make a city, and so on.
I like that example :-)
> Higher-level concepts in your system exhibit a one-to-many relationship with lower-level phenomena, not a one-to-one match.Yeah. That is called 'multiple realisability' or probably 'realizability' in US english.
A problem with the brain is neural plasticity. Different brains are like... Different trees or shrubs where there is similarity in overall shape and in certain features but also vast differences in how different individuals brains are wired. Like branches and twigs and leaves. There is considerable variation across the population. Considerable. One person might have a lesion in one particular site with a precise functional deficit as a consequence and another person might have a lesion in a similar site with no functional deficit as a consequence. Of course one could try and say that there are differences it is just that they are too small for us to notice. That might be right but it seems that a better explanation is that different peoples brains are wired differently so you can't map function very well between individuals. It is very complicated.Take A B C D E as people with x disorder.
Do an fMRI scan of them.
Superimpose one scan on another scan on the next scan etc (average the results).
You end up with a model (one scan) of 'people with x disorder'.Take F G H I J as normal controls.
Do an fMRI scan of them.
Superimpose one scan on another scan on the next scan etc (average the results).
You end up with a control (one scan) of 'normal people'.What I worry about is...
Take K L M N O as normal controls2.
Do an fMRI scan of them.
Superimpose one scan on another scan on the next scan etc (average the results).
You end up with controls2 (one scan) of 'normal people2'.Are there noticable differences between 'normal people' and 'normal people2'? I don't know the unit of measurement... What is the scan supposed to show? Neural activation (deduced from metabolisation of sugar or somesuch...). I don't know the scale... But you need to decide on how to assign colours to numerical differences. How you decide that will make a considerable difference for how normals and normals2 look similar / different. Kind of like choosing an appropriate scale so your graph is visually most striking.
Are there more differences between 'disorder x' and 'normals' than there is between 'normals' and 'normals2'? Just how similar is F to G anyway?
Is it more likely that A will have a brain more similar to 'normal' or to 'disorder x'?
I don't know... But these are my worries about the significance of fMRI findings. (Yes I appreciate that sample size is much larger).
Posted by Estella on September 2, 2006, at 12:44:34
In reply to Re: Biopsychosocial vs Biological Reductionism » finelinebob, posted by Estella on September 2, 2006, at 12:39:38
Lets say that A's brain is more normal than similar to the average of disorder x.
Lets say that the average of disorder x have 'heightened activity in region y'.
Lets say that people say 'people with disorder x have heightened activity in region y'.
Lets say that people say 'individual A has disorder x because they have heightened activity in region y'.
Lets say that individual A is given drug B because drug B reduces activity in region y.
Er... How do we know that drug B reduces activity in region y?? Does it do this for each individual in a group or on the basis of averages once more?
Even if individual A does have heightened activity in region Y what does that do for A?
There might be another individual Z that has heightened activity in region Y yet this person is a model of psychological health.
What would reducing activity in region Y do for Z?
Doesn't anybody else worry about this?
Am I missing something?
(Lol more to the point... What am I missing?)
Posted by Estella on September 2, 2006, at 12:56:18
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by SLS on September 2, 2006, at 6:33:49
We don't have very good models of any disorder on any level of analysis. I mean... There are models but they aren't particularly good. I guess people are trying to make them better. Hard to know whether you want a model on one level of explanation (so you have a model for each level of explanation) or whether you could make a model that is interlevel.
> Fortunately, both the reductionist and the psychosocial perspectives are in place to research problems involving the microscopic and the macroscopic. Of course, there are people who integrate both into their approach to understanding mental illness. It's not that hard.
Well... There is still a lot of division. Different people work within different frameworks and talk past each other a little and ignore each others results etc.
Sure, progress is being made. But there is still a lot of talking past.
I'm not sure that I've nailed a justification for multi-leveled models given supervenience (logical dependence of high level processes on low level processes). I mean... There is a pragmatic argument but I'd like a logical one too.
I'm also interested in whether different levels might be fundamental for different disorders or whether every disorder is best given an interlevel explanation.
It can be hard to see how to offer a good detailed interlevel model.
E.g., there are good cognitive models of autism as theory of mind deficit. I don't know whether they have done neuro-imaging to try and localise a 'theory of mind' module... Some people think there is a theory of mind module. They might be cognitive psychologists, however, I'm not sure how neuroscience feels about a purported localisation of a theory of mind module. If neuroscience can't find one then...
Have they falsified the cognitive explanation...
Or is cognitive psychology sufficiently autonomous from neuroscience to be able to say 'different individuals brains implement theory of mind differently'.Dunno.
There were social models of autism. Don't know if there are anymore (I'm thinking of the 'old' theory about parenting. Don't know whether more research has been done into social factors though).
Seems possible that different things could be relevant to different individuals.
Lets say the following are causal factors for anxiety (in the sense of being sufficient but not necessary)
- endocrine system
- crappy environmentare there two kinds of anxiety (the first kind and the second kind) or is anxiety multiply realised? don't know... but taxonomy might change...
i think someone or other claimed to have found... 5 kinds of premenstrual disorder (mental health kind of disorder)
But it is funny that most people get to be NOS.
Posted by yxibow on September 2, 2006, at 13:54:27
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by Estella on September 2, 2006, at 12:56:18
> We don't have very good models of any disorder on any level of analysis. I mean... There are models but they aren't particularly good. I guess people are trying to make them better. Hard to know whether you want a model on one level of explanation (so you have a model for each level of explanation) or whether you could make a model that is interlevel.
Well we have fairly good models of OCD but its not clear to me that you may have not read any of the references pointed out.
We have some, but not all models of schizophrenia, having been studied for many decades, starting with rather poor medicational approaches to more modern and humane treatment methods. Schizophrenia is one of the few neurochemical disorders that can theoretically to the best of my knowledge be seen on MRIs simply because some forms are neurodegenerative. But they can certainly be seen on SPECT/PET.
> There were social models of autism. Don't know if there are anymore (I'm thinking of the 'old' theory about parenting. Don't know whether more research has been done into social factors though).
>
> Seems possible that different things could be relevant to different individuals.
Its possible, but I do believe we will find, and already are starting to find genetic reasons for autism. It is the flat earth society reasoning, pardon the phraseology however, that continues to blame from fluoride in the water to nonexistant levels of methanol from aspartame for every possible cause of autism or developmental disorders because they want desperately and understandably to find a reason.
> Lets say the following are causal factors for anxiety (in the sense of being sufficient but not necessary)
>
> - endocrine system
> - crappy environment
>
> are there two kinds of anxiety (the first kind and the second kind) or is anxiety multiply realised? don't know... but taxonomy might change...
ALL anxiety whether introduced environmentally ("crappy environment" -- please dont assume what peoples environment are like or how they assimilate their surroundings or life upbringings, that is insulting) or by "a faulty endocrine system" which I assume you mean thyroidal are inherently as neurochemical as this seemingly antediluvian thread. The thoughts you bring to the table came from free will, which in turn came from your mind cogitating, which produced brain activity and neuronal firing and can be seen on an EKG and a SPECT scan.
> But it is funny that most people get to be NOS.Do please refrain from continuing to use the word funny in your hypothesis, its not amusing to those who are on here and are diagnosed with a disorder yet to be determined. There are various DSM-IV and DSM-V disorders that are indeed NOS. They don't fit into a regular category of a DSM diagnosis, e.g. psychosis NOS. Until perhaps more is diagnosed in the term of treatment.
Posted by SLS on September 2, 2006, at 16:02:42
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 2, 2006, at 11:59:34
> > > The colours that are chosen to represent different levels of activation are completely arbitrary.
>
> > They are not arbitrary. Red is hot and blue is cold.
>
> So the scans show the temperature of different parts of your brain?Yes.
- Scott
Posted by SLS on September 2, 2006, at 16:43:01
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 2, 2006, at 11:59:34
> > > > The colours that are chosen to represent different levels of activation are completely arbitrary.
> >
> > > They are not arbitrary. Red is hot and blue is cold.
> >
> > So the scans show the temperature of different parts of your brain?
>
> Yes.Well, ok, no.
Wait!
Ok.
No.
I'm sure you understood the concept. The colors were not chosen arbitrarily. The colors do have meaning in our society.
- Scott
Posted by finelinebob on September 2, 2006, at 18:41:59
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 2, 2006, at 11:59:34
> > > The colours that are chosen to represent different levels of activation are completely arbitrary.
>
> > They are not arbitrary. Red is hot and blue is cold.
>
> So the scans show the temperature of different parts of your brain?
>Pardon me, but let me just interject some color theory into the mix. Lots of ways of describing color, but let's talk about HSV/HSB -- hue (color), saturation (intensity of the color compared to gray=0) and value or brightness (where it is on a scale from black to white) --the common colorspace for Photoshop, for instance. What I find interesting about most color mapping techniques is that while Hue is used to map different values of what is measured, Saturation is always at like 100%. To choose red to indicate high amounts of X being measured and violet to measure low amounts of X being measured, that choice might be completely arbitrary although the visual spectrum is "respected" in mapping colors inbetween deep violet and deep red.
But choosing red for "hot" meaning high energy levels and blue for "cool" or low energy levels is not completely arbitrary. In Western Culture, those two color-energy relationships are widely prevalent, so picking them to represent level of activity for whatever your machine measures, converting the numerical to the visual, is a natural "bias" to follow. People can relate to it readily.
What may NOT be arbitrary, tho, is the Brightness. I don't see this so much with, say, mapping non-visible wavelengths of radiation to the visible spectrum for x-ray spectroscopy of stellar objects. However, with mapping brain scanning technologies and what they measure to the visual spectrum, there is a distinct bias in lowering the Brightness of "cooler" areas. Although the colors remain vivd as much as they can, they do fade to black.
AFAIK, there is no scientific reason for this. Changing the brightness not only does not add to the interpretation of, say, a PET scan, it actually introduces a non-existent variable or, rather, a variable indicating the "goodness" or the "badness" implicated by the colors.
Any particular unstable radioisotope will decay, and the decay event may have a variety of outcomes. We know of isotopes whose decay events have one particular outcome that accounts for, say, 90% of all possible outcomes. That decay event will release a photon of a precise wavelength. When such an isotope in introduced into the bloodstream, areas of increased bloodflow will naturally display a greater number of events than areas with decreased bloodflow.
In other words, we are looking at a single dimension, a single degree of variation: the number of decay events. Any visual mapping of that information requires exactly one visual element to be altered. So, all any brainscan needs to do would be to map event counts to Hue OR Saturation OR Brightness. The use of Hue AND Brightness (with red having B near 100 and violet having B near 0) introduces a bias ... which I think depending on the situation can favor a favorable or unfavorable dx. An "unbiased" mapping would have no "fade to black" -- in those edges of the brain/skull/scalp where the bloodflow terminates, there is no topographical reason not to maintain an equal value for all hues until you hit a region of no recorded events; which could be white or black according to your preference as the mapper.
That being said, I have no problem with biases in scientific observations since I don't believe in objectivity -- but you need to acknowledge your biases for what they are if you're going to have any degree of intellectual integrity or honesty.
As an aside, I always find it a bit amusing that red tends to be assigned to high evergy levels and violet to low energy levels. The physicist in me just wants to giggle at how they got it backwards.
Posted by finelinebob on September 2, 2006, at 23:31:37
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by finelinebob on September 2, 2006, at 18:41:59
... I'm out.
It's been fun, but I don't get paid enough by Babble to spend the time I just spent getting halfway thru a response before I realized enough was enough.
;^)
You can take the academic out of the academy, but that ain't gonna shut him up....
Posted by Estella on September 2, 2006, at 23:50:25
In reply to Re: Biopsychosocial vs Biological Reductionism » Estella, posted by yxibow on September 2, 2006, at 13:54:27
> Well we have fairly good models of OCD
I guess 'fairly good' is relative. The models we have now are better than the models we used to have, that is true.
> but its not clear to me that you may have not read any of the references pointed out.
I'm afraid I haven't had time to get to them yet. I will at some point. I've been reading about modelling in psychiatry more generally. People talk about schizophrenia and autism and depression and anxiety and alzheimers etc a lot. I've read a tiny bit about OCD but that is probably the disorder I'm least familiar with. I look forward to getting to it at some point :-)
> Schizophrenia is one of the few neurochemical disorders that can theoretically to the best of my knowledge be seen on MRIs simply because some forms are neurodegenerative. But they can certainly be seen on SPECT/PET.Christopher Frith has done a lot of work on that "The Cognitive Neuro-Psychology of Schizophrenia". That is where I found out about their not being markers within individuals (you can't dx schizophrenia on the basis of fMRI) but there are differences when you look at averages across the population. He said that the neural differences tended to be correlated with the most severe cases. He also considered the possibility that schizophrenia isn't a natural kind, rather there are different kinds of disorders that have been thrown together.
> Its possible, but I do believe we will find, and already are starting to find genetic reasons for autism.Trying... Not doing so well. Not doing so well with the genetic markers for schizophrenia either. Several different genes seem to be implicated but whether they are expressed or not depends on certain other genes. Also social influences. Perhaps whether the mother had an infection / virus in the third (?) Trimester. But none of those are sufficient and I don't know that any of those are necessary too. So the model is fairly vague indeed...
> > Lets say the following are causal factors for anxiety (in the sense of being sufficient but not necessary)
> > - endocrine system
> > - crappy environment> > are there two kinds of anxiety (the first kind and the second kind) or is anxiety multiply realised? don't know... but taxonomy might change...
> ALL anxiety whether introduced environmentally ("crappy environment" -- please dont assume what peoples environment are like or how they assimilate their surroundings or life upbringings, that is insulting)I wasn't assuming anything. The 'Lets say that' should have clued you in to the fact that I was speaking hypothetically. I replace what I said above with the following:
Lets say the following are causal factors for anxiety (in the sense of being sufficient but not necessary)
A
B
C
D
Eare there 5 kinds of anxiety (one for each aetiological factor) or is anxiety multiply realised? don't know... but taxonomy might change...
> > But it is funny that most people get to be NOS.
> Do please refrain from continuing to use the word funny in your hypothesis, its not amusing to those who are on here and are diagnosed with a disorder yet to be determined.I meant funny as in strange, not funny as in ha ha. I know it isn't ha ha funny.
> There are various DSM-IV and DSM-V disorders that are indeed NOS. They don't fit into a regular category of a DSM diagnosis...
Yep. So more people with mental illness don't fit into a regular category than people who do fit into a regular category (or 5). I guess that I think that that shows us that the regular categories are inadequate.
Posted by Estella on September 2, 2006, at 23:57:26
In reply to Re: Biopsychosocial vs Biological Reductionism » Estella, posted by SLS on September 2, 2006, at 16:43:01
lol ((((SLS))))
> I'm sure you understood the concept. The colors were not chosen arbitrarily. The colors do have meaning in our society.
I think I get what you are saying
But I think that the way the common conventional meaning relates to the common way of representing fMRI scans is unclear.I'm sure I've seen yellow and green on them.
Is yellow 'hotter' than 'green'?
?
Is blue 'hotter' than green?
Posted by Estella on September 3, 2006, at 0:01:22
In reply to And with that..., posted by finelinebob on September 2, 2006, at 23:31:37
> ... I'm out.
> It's been fun, but I don't get paid enough by Babble to spend the time I just spent getting halfway thru a response before I realized enough was enough.
> ;^)Aw.
:-(
But yeah, okay, fair enough, I understand. I love to have these conversations but yeah I understand what you are saying about time permitting. Sometimes I have to walk away from them too. That being said I enjoy them very much. I'd like to thank everyone who has participated. I've learned something from all of you and it helps me with my work.> You can take the academic out of the academy, but that ain't gonna shut him up....
Yeah :-)
I'm supposed to be writing this up... But often what I find is... Babblers give me great ideas and question me in surprising ways and so forth. I find my academic work benefits from these conversations. But that being said there comes a time when I have to go ENOUGH! And I have to stop Babbling and just write the darned paper.You are free to float in and out of these conversations. I know what you mean by time consuming... Its consumed a lot of my time over the past few days.
Thanks for your other post... I will respond to it properly but I understand if you bow out.
((((Guys))))
:-)
Posted by Estella on September 3, 2006, at 1:03:22
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by finelinebob on September 2, 2006, at 18:41:59
> What may NOT be arbitrary, tho, is the Brightness.
I guess the scale is arbitrary. I don't know the scale for fMRI's but I figure they have to pick a scale for when blue becomes green becomes red etc. I figure the scale they use is fairly arbitrary and if you change the scale you would end up with a different looking fMRI. Different colours at different patches.
The colour stuff is interesting. I didn't know all that.
> Changing the brightness not only does not add to the interpretation of, say, a PET scan, it actually introduces a non-existent variable or, rather, a variable indicating the "goodness" or the "badness" implicated by the colors.
I find that very interesting indeed.
:-)> That being said, I have no problem with biases in scientific observations since I don't believe in objectivity -- but you need to acknowledge your biases for what they are if you're going to have any degree of intellectual integrity or honesty.
Yeah. They have implications for how the results are legitimately interpreted.
> As an aside, I always find it a bit amusing that red tends to be assigned to high evergy levels and violet to low energy levels. The physicist in me just wants to giggle at how they got it backwards.I didn't know it was reversed in physics. My knowledge of physics is exhausted from what I've posted about it in this thread. All I know... Is there is math in physics and I'm not so hot at math ;-)
Thanks for your post.
I'm sure I will return to it at some point
(When I look at fMRI's in more detail):-)
Posted by finelinebob on September 3, 2006, at 1:45:22
In reply to Re: Biopsychosocial vs Biological Reductionism » finelinebob, posted by Estella on September 3, 2006, at 1:03:22
ROY G BIV, Estlla, ROY G BIV ...
... or VIB G YOR, since they got it backwards.
Mathemagically, it's prolly pretty simple. You have A as your lowest detectible count or just set it to 1, black being 0. You have Z has the highest detected count. Violet light has a short wavelength (low number), red a long wavelength (high number). Match your lowest violet to A, your highest red to Z, and let the computer figure out the rest in-between.
Of course, the visible spectrum expressed that way is a linear progression. If your theory behind what you're studying suggests a non-linear response, then you have to get tricky.
> > Changing the brightness not only does not add to the interpretation of, say, a PET scan, it actually introduces a non-existent variable or, rather, a variable indicating the "goodness" or the "badness" implicated by the colors.
>
> I find that very interesting indeed.
> :-)It's like this:
Say I'm doing a PET scan of a stroke patient trying to read something and I get lots of yellow and red (woohoo!) in the visual cortex but blue to violet to black wherever it is in our brains that turns those visual stimuli into language and then meaning ... uh oh.
Then again, I got this pre-chemo scan of a patient with a tumor somewhere, all nasty bright yellow and red (boo!) but then I put up the post-chemo scan and that area is now blue to violet to black. Coooooll! (figuratively and literally)
> > As an aside, I always find it a bit amusing that red tends to be assigned to high evergy levels and violet to low energy levels. The physicist in me just wants to giggle at how they got it backwards.
>
> I didn't know it was reversed in physics.Yep. Particularly if you are measuring something like decay events from a radiological tracer. Each event is a little ping of energy on the scanner's sensors. Lots of pings, lots of energy.
Well, when it comes to the visible spectrum, red is at the low energy end and violet at the high evergy end. ROY G BIV (red orange yellow green blue indigo violet) is the spectrum from low to high energy. So for red to represent areas of high activity is to abandon science and cave in to cultural biases of what's hot and what's not.
Come to think of it, they DO do this even in astronomy. Nothing's sacred.
Posted by Estella on September 3, 2006, at 6:45:57
In reply to Guess I couldn't stay away completely..., posted by finelinebob on September 3, 2006, at 1:45:22
> ROY G BIV, Estlla, ROY G BIV ...
Yeees. Multi-guess psychophysics is coming back to me :-)
> ... or VIB G YOR, since they got it backwards.
Well now, that just don't sound pretty ;-)
> Mathemagically, it's prolly pretty simple. You have A as your lowest detectible count or just set it to 1, black being 0. You have Z has the highest detected count. Violet light has a short wavelength (low number), red a long wavelength (high number). Match your lowest violet to A, your highest red to Z, and let the computer figure out the rest in-between.Okay. Thanks. I didn't know that. Though I'm worried about the computer 'figuring out' stuff...
> Of course, the visible spectrum expressed that way is a linear progression. If your theory behind what you're studying suggests a non-linear response, then you have to get tricky.Woo hoo!!! Thats what I was thinking. Now hang on. I f*cked up my word for the week (abberant) so maybe I f*cked up my math for the week too.
Linear (a):
Non linear: (the restWoo hoo. Also... Ah... Thats what log is for ;-)
Do they use linear or non linear for colour distributions on the scan do you know?
> Say I'm doing a PET scan of a stroke patient trying to read something and I get lots of yellow and red (woohoo!) in the visual cortex
So they are processing visual stimuli...
> but blue to violet to black wherever it is in our brains that turns those visual stimuli into language and then meaning ... uh oh.
Ah.
Though sometimes different people have different localisations. So (for example) if you have damage to the left hemisphere as a fetus then you can develop language production and comprehension (for example) in the right hemisphere.
> Then again, I got this pre-chemo scan of a patient with a tumor somewhere, all nasty bright yellow and red (boo!)
High activity at tumor sites?
Are lesions different?The colour stuff was interesting, thanks for that :-)
Posted by SLS on September 3, 2006, at 7:14:52
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 2, 2006, at 23:57:26
> lol ((((SLS))))
>
> > I'm sure you understood the concept. The colors were not chosen arbitrarily. The colors do have meaning in our society.
>
> I think I get what you are saying
> But I think that the way the common conventional meaning relates to the common way of representing fMRI scans is unclear.
>
> I'm sure I've seen yellow and green on them.
> Is yellow 'hotter' than 'green'?Yes.
> Is blue 'hotter' than green?
No.
I think the colors follow the colors of the visible spectrum from blue to red as cold to hot; inactive to active; sparse to dense.
- Scott
Posted by finelinebob on September 3, 2006, at 20:58:29
In reply to :-) » finelinebob, posted by Estella on September 3, 2006, at 6:45:57
> > Mathemagically, it's prolly pretty simple. You have A as your lowest detectible count or just set it to 1, black being 0. You have Z has the highest detected count. Violet light has a short wavelength (low number), red a long wavelength (high number). Match your lowest violet to A, your highest red to Z, and let the computer figure out the rest in-between.
>
> Okay. Thanks. I didn't know that. Though I'm worried about the computer 'figuring out' stuff...Bah! It's z-normalization essentially, without a set of negative values. Say your mapping program has the capability of displaying 98 hues plus black and white. Say your density counts range from 65 to 1380, min/max across all subject in your study. You may want to artificially (or perhaps theoretcially) set the min of your count range to 0, then again you might accept "65" as the minimal blood flow for least activation of the region studied. For a linear relationship, converting a scale of 1315 steps to 100 step is simple math -- we do it all the time to convert Celsius to degrees Fahrenheit. It's arithmatic, pure and simple.
> > Of course, the visible spectrum expressed that way is a linear progression. If your theory behind what you're studying suggests a non-linear response, then you have to get tricky.
>
> Woo hoo!!! Thats what I was thinking. Now hang on. I f*cked up my word for the week (abberant) so maybe I f*cked up my math for the week too.
>
> Linear (a):
> Non linear: (the rest
> ...
> Woo hoo. Also... Ah... Thats what log is for ;-)Logarthimic relationships are only one type of non-linear relationships. but any of them can be mapped to a linear scale with the proper transformation function.
> > Do they use linear or non linear for colour distributions on the scan do you know?No idea. I'd have to say the relationship is determined by the underlying theory. For instance, inscreased brain activity for a particular region on a particular task might show an exponential instead of linear increase in bloodflow to that region.
> High activity at tumor sites?
> Are lesions different?1) I'd imagine so. Biology is too squishy for me, but from what I understand tumors are sites of abnormally rapid cell growth. Sounds like it would require lots of artery and capillary formation. Denser blood supply - more pings.
2) Now you're getting into what **I** understand the term "brain plasticity" to mean. My father's second stroke damaged part of his language center, causing some aphasia. Any lesion cause by the stroke I'd imagine would show up blue to black.
Now, in his OT sessions, they gave him lots to read and lots of crosswords to do. He still has very limited aphasia, but nowhere near as bad as it was. Had he been getting his brain scanned while doing that language-heavy mental work, I'm guessing that area would have relatively "lit up" as his brain rewired itself around the lesion (if that's the theory you believe) or different, unexpected areas of his brain would have lit up (if that's the theory you believe).
Anyway, long time since I read anything about brain plasticity and I was never really into pure neuropsych as it was, so just my $0.02.
Posted by Estella on September 3, 2006, at 22:49:13
In reply to Re: :-) » Estella, posted by finelinebob on September 3, 2006, at 20:58:29
I don't really know anything about the nitty gritty of neuro-imaging. I remember a bit for the multi-guess quizzes but I think it was stuff that I crammed and promptly forgot. I will need to return to it at some point, though. When I do modelling in neuro-psychology. Thanks for explaining it to me.
> Bah! It's z-normalization essentially
eh?
(its okay, you don't have to explain that)> Logarthimic relationships are only one type of non-linear relationships.
figures ;-)
> No idea. I'd have to say the relationship is determined by the underlying theory.Goodie :-)
> Biology is too squishy for me
Me too, but the theory is okay :-)
> tumors are sites of abnormally rapid cell growth. Sounds like it would require lots of artery and capillary formation. Denser blood supply - more pings.
I see. That makes sense. I guess you would differentiate between a tumor and an active area because tumors would be more localised. I think that scar tissue can become the focus of a seizure too (where a seizure is increased activity). Thats kinda interesting...
> Now you're getting into what **I** understand the term "brain plasticity" to mean.:-)
My father's second stroke damaged part of his language center, causing some aphasia. Any lesion cause by the stroke I'd imagine would show up blue to black.
Yep.
> Now, in his OT sessions, they gave him lots to read and lots of crosswords to do. He still has very limited aphasia, but nowhere near as bad as it was.Yeah. If he had had the stroke earlier in life he would have probably regained even more or close to complete or even complete function.
> Had he been getting his brain scanned while doing that language-heavy mental work, I'm guessing that area would have relatively "lit up" as his brain rewired itself around the lesion (if that's the theory you believe) or different, unexpected areas of his brain would have lit up (if that's the theory you believe).
Yeah :-) I think that usually it is areas that are close. Though it depends on the task. Most people have language production / comprehension localised in the left hemisphere. A small percentage have it localised in the right. A tinier percentage have bi-lateral speech control. If you have severe damage to your left hemisphere when you are very young then I think your right hemisphere takes over the function. I think that people who are blind from birth have areas that normally process visual information processing auditory information. All those are extreme examples but there is a lot of variation in different peoples brains (which complicates working out localisations across the population).
If you acquire non-cortical blindness when you are a kid I'm not sure if the visual areas start to process auditory stimuli. If you acquire non-cortical blindness late in life I'm not sure if the visual areas start to process auditory stimuli. I'm not sure that ALL individuals who are born blind start to process auditory information with what are typically visual processing areas. I guess there is probably... Considerable variation across individuals.
Er... Do you know what kind of aphasia he had?
I think there are lots of different aphasias for different kinds of task etc. Lots of different language ones too. I've heard that some people can (temporarily) lose categories of flora. Other people can (temporarily) lose categories of fauna. That suggests that the concepts for those categories may be somewhat localised. Makes some kinda evolutionary sense. Don't know if you can lose the categories for kinds of cars (without losing other categories besides that).
Posted by Estella on September 3, 2006, at 22:50:41
In reply to Re: Biopsychosocial vs Biological Reductionism » Estella, posted by SLS on September 3, 2006, at 7:14:52
> I think the colors follow the colors of the visible spectrum from blue to red...
Yeah.
> as cold to hot; inactive to active; sparse to dense.
Though finelinebob was saying that the colour spectrum is inverted from how it is in physics (red should be low activity because it is... low frequency?)
Posted by finelinebob on September 4, 2006, at 0:36:25
In reply to Re: :-) » finelinebob, posted by Estella on September 3, 2006, at 22:49:13
> > Bah! It's z-normalization essentially
>
> eh?
> (its okay, you don't have to explain that)In stats, you can compare measurements of two different things by z-normalizing their measured values. Set the mean to 0. Set the standard deviation to 1. Adjust distrutions accordingly.
It's like comparing apples to oranges by changing them both into pears.
> Er... Do you know what kind of aphasia he had?Nope. I do remember that he had about 85% chance of correctly expressing what he wanted to say by writing it instead.
Posted by finelinebob on September 4, 2006, at 0:47:22
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 3, 2006, at 22:50:41
> Though finelinebob was saying that the colour spectrum is inverted from how it is in physics (red should be low activity because it is... low frequency?)
Red photons are lower in energy than violet photons.
The "infra" in infrared means "below". The "ultra" in ultraviolet means "beyond". Terminology, again, based on energy.
If "hot spots" on a scan are a measurement of high levels of energy, a scientifically "honest" mapping would make violet hot and red cold ... but the culturally honest mapping of making red "hot" may make scans easier to interpret, since pre-meds never take physics seriously.
Posted by Estella on September 4, 2006, at 1:16:53
In reply to Re: :-) » Estella, posted by finelinebob on September 4, 2006, at 0:36:25
> It's like comparing apples to oranges by changing them both into pears.of course, that makes perfect sense ;-)
> Nope. I do remember that he had about 85% chance of correctly expressing what he wanted to say by writing it instead.
I see.
I don't know my aphasias very well...
It is pretty interesting, though.
We had a guy back home in the psych department who was interested in neurological testing.
If you did some of his post grad courses you would end up with a diploma to administer neurological tests (and could get a job up at the hospital doing that 'cause he was part time at uni and mostly in the hospital). But then he left. They kept up with the courses but the numbers dropped because whoever took over wasn't accredited to teach people to administer the tests.I remember him from under-grad courses though. He was fairly interesting :-) Had lots of anecdotes and stuff :-)
Posted by SLS on September 4, 2006, at 6:01:02
In reply to Re: :-) » Estella, posted by finelinebob on September 3, 2006, at 20:58:29
> 1) I'd imagine so. Biology is too squishy for me, but from what I understand tumors are sites of abnormally rapid cell growth. Sounds like it would require lots of artery and capillary formation. Denser blood supply - more pings.
Also, cancer tissue has a greater metabolic rate, as the cells are rapidly dividing. It takes up and uses glucose faster than the tissue surrounding it. Thus, radiolabelled glucose, fluorodeoxyglucose (FDG), is used frequently in P.E.T. scans to identify tumors.
- Scott
Posted by SLS on September 4, 2006, at 6:18:31
In reply to Re: Biopsychosocial vs Biological Reductionism » SLS, posted by Estella on September 3, 2006, at 22:50:41
> > I think the colors follow the colors of the visible spectrum from blue to red...
>
> Yeah.
>
> > as cold to hot; inactive to active; sparse to dense.
>
> Though finelinebob was saying that the colour spectrum is inverted from how it is in physics (red should be low activity because it is... low frequency?)cold as blue glacial ice = low energy (temperature)
hot as red glowing metal = high energy (temperature)
We have blue to signify cold water and red to signify hot. I don't know if these color associations are somehow intuitive or simply taught culturally. Fire is rarely blue, but very often yellow, orange, and red. It is interesting that radiant heat is conveyed in the infrared region of the spectrum. The decision to design the computer program to essentially "reverse" the spectral portrayal of energies in is interesting. It works sort of like a weather map.
- Scott
Posted by finelinebob on September 4, 2006, at 17:30:48
In reply to Re: Biopsychosocial vs Biological Reductionism » Estella, posted by SLS on September 4, 2006, at 6:18:31
> cold as blue glacial ice = low energy (temperature)
>
> hot as red glowing metal = high energy (temperature)
>
> We have blue to signify cold water and red to signify hot. I don't know if these color associations are somehow intuitive or simply taught culturally. Fire is rarely blue, but very often yellow, orange, and red. It is interesting that radiant heat is conveyed in the infrared region of the spectrum. The decision to design the computer program to essentially "reverse" the spectral portrayal of energies in is interesting. It works sort of like a weather map.It is completely cultural.
I'd imagine ice thick enough to appear green to blue is scattering light for reasons similar to why the sky is blue.
Of course, the word "heat" and how it is used is just a cultural artifact in itself, but infrared radiation happens to have wavelengths larger but similar to molecular sizes so when some IR "hits" an object, the molecules get a bit more energy to move around and that motion is what we call heat.
Ultraviolet light is also pretty close, but on the small end in terms of wavelength. Because it's smaller, it can pass through some materials without really affecting them, get absorbed then spit back out as something else. White clothes glowing under UV light means that non-visible radiation is being re-emitted as visible light ... then there's the photoelectric effect -- Einstein's Nobel Prize came from his work on this -- where UV light hitting metal can create an electric charge or current flow.
As for flames being blue -- any welder or chemist can tell you that a blue flame has a higher temperature (typically from more efficient combustion of a gas, like with an acetylene torch or Bunsen burner) than red flames. Same thing if you have a gas stove. But other than gas stoves and pilot lights on water heaters, I can't think of many common situations where combustion is efficient enough to raise temperatures that high.
Posted by SLS on September 4, 2006, at 19:36:05
In reply to Re: Biopsychosocial vs Biological Reductionism, posted by finelinebob on September 4, 2006, at 17:30:48
> > cold as blue glacial ice = low energy (temperature)
> >
> > hot as red glowing metal = high energy (temperature)
> >
> > We have blue to signify cold water and red to signify hot. I don't know if these color associations are somehow intuitive or simply taught culturally. Fire is rarely blue, but very often yellow, orange, and red. It is interesting that radiant heat is conveyed in the infrared region of the spectrum. The decision to design the computer program to essentially "reverse" the spectral portrayal of energies in is interesting. It works sort of like a weather map.
>
> It is completely cultural.
>
> I'd imagine ice thick enough to appear green to blue is scattering light for reasons similar to why the sky is blue.
>
> Of course, the word "heat" and how it is used is just a cultural artifact in itself, but infrared radiation happens to have wavelengths larger but similar to molecular sizes so when some IR "hits" an object, the molecules get a bit more energy to move around and that motion is what we call heat.
>
> Ultraviolet light is also pretty close, but on the small end in terms of wavelength. Because it's smaller, it can pass through some materials without really affecting them, get absorbed then spit back out as something else. White clothes glowing under UV light means that non-visible radiation is being re-emitted as visible light ... then there's the photoelectric effect -- Einstein's Nobel Prize came from his work on this -- where UV light hitting metal can create an electric charge or current flow.
>
> As for flames being blue -- any welder or chemist can tell you that a blue flame has a higher temperature (typically from more efficient combustion of a gas, like with an acetylene torch or Bunsen burner) than red flames. Same thing if you have a gas stove. But other than gas stoves and pilot lights on water heaters, I can't think of many common situations where combustion is efficient enough to raise temperatures that high.Yeah. I forgot about Bunsen burners. It's been too long since school.
:-)
- Scott
This is the end of the thread.
Psycho-Babble Medication | Extras | FAQ
Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.org
Script revised: February 4, 2008
URL: http://www.dr-bob.org/cgi-bin/pb/mget.pl
Copyright 2006-17 Robert Hsiung.
Owned and operated by Dr. Bob LLC and not the University of Chicago.