# Questions Regarding Human Brain



## RobynC (Jun 10, 2011)

The human brain reaches full size early on in life however I've received conflicting information about exactly at what ages when a typical male and female brain reaches 

1.) Full volume
2.) Full mass and surface area.
3.) Maximum surface area


R.C.


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## Agile (Sep 27, 2010)

disregard.....


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## RobynC (Jun 10, 2011)

I'm sorry, I don't understand?


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## Wulfyn (May 22, 2010)

If I remember correctly the answer to the surface area & volume is around 12, and mass is around 14.


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## Khar (May 21, 2011)

The reason you have received conflicting information in largely due to the fact that the brain is not static in its growth, nor are parts of the brain growing at the same rate for the same period of time (1). As seen in that article, there is also differentiation between genders, with female brains showing greater myelination, effectively improving their skills over men in writing and so forth for the age-group 6-29, while leaving us vulnerable to various forms of psychopathy. The continued growth of the brain is largely due to allowances for the brain to continue to grow and improve over time, well past the early stages of rapid brain growth and development in the immediate post-natal phase (2). 

Hence, depending on how it is described, the bulk of brain growth or complete brain growth, conflicting information is expected. Always remember to look at the precise wording of phrases and the use of nomenclature in scientific papers. To answer your question, both men and women peak in the size (weight-wise) of their brain from 19-21. This should not be mistaken for being an actually mature brain, which are generally considered by literature not to be mature until at least the mid-twenties for both men and women. However, it is pretty much done growing by the age of 2 or 3, and does not reduce back down to that level following 21, not even 60 years later, showing a persistence in brain size in the long-term, even if it does diminish. It is assumed that, though the female brain is smaller, increased and deeper folds allow for similar brain size in terms of surface area. 

The answer to the rest of your question will be difficult. In general, we don't know a lot about the morphology of brains, and the sizes of brains vary greatly. However, generally they fall within the range of 1,500 to 2,000 square centimeters for both genders, estimated. Other sources have indicated a maximum end of 2,500 centimeters squared. The depth of these wrinkles, called fissures for the deep ones or sulcus (sulci pl.) for the shallow ones, decreases over time, more heavily in the multimodal areas, reducing overall surface area. Factors which increase the amount of these could persist to as long as 30 years of age. 

As a final note, our brains are always developing, and none of these sizes or times should be considered the fully developed point of our brains in and of themselves.

EDIT: In response to @RobynC below, as the link I used shows, 80% is around that. Hence why I said "pretty much done." I believe you have accidentally misinterpreted my post.


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## RobynC (Jun 10, 2011)

@Khar

I find the claim that the brain would be at full size by 2 years of age highly suspicious. I do remember hearing it would be around 80% size at that point. I don't know how much more after that it reaches full size though. One source said 6 years of age, others teenage-years.


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## Wulfyn (May 22, 2010)

I'm getting all of this from my memory but I think that the ages listed by you Khar are on the late side. I was taught that peak weight occurred at around 14, as this is when myelination had completed it's final stage in the frontal lobe. By the time you hit around 20 you had lost a little weight to the brain due to neuronal pruning.

I also didnb't think that it had reached around 80% until the age of around 6 when it stops growing for a while, before hitting another groth burst pre-puberty, maxing at around 12. This is why a lot of the higher cognitive functions (e.g. logic) don't kick in until between that part and when the frontal lobe myelination has finished.

We get better at rationalisation through our teens as neurons are pruned. This helps reduce the 'noise' of neural activity, which is often why the brain is not considered as mature until the early 20's, when it is at peak performance.


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## RobynC (Jun 10, 2011)

@Wulfyn



> I also didnb't think that it had reached around 80% until the age of around 6 when it stops growing for a while, before hitting another groth burst pre-puberty, maxing at around 12.


So full volume is reached at 12? 


R.C.


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## RobynC (Jun 10, 2011)

I remember hearing something about people with autism having more brain-cells and a higher brain-mass. This apply to all autistics?


R.C.


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## RobynC (Jun 10, 2011)

Nobody at all?


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## Wulfyn (May 22, 2010)

I don't remember learning anything like that, I think it is just down to wiring - specifically around the frontal lobe. Sorry I can't be more specific.


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## Psychosmurf (Aug 22, 2010)

RobynC said:


> I remember hearing something about people with autism having more brain-cells and a higher brain-mass. This apply to all autistics?
> 
> 
> R.C.


Don't know for sure but I heard people with autism and Asperger's Syndrome have increased gray matter depth.


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## RobynC (Jun 10, 2011)

@Psychosmurf

Allegedly I remember hearing more recently that autistic brains mature slower than most people. This seems to involve a greater gray-matter depth as you mentioned earlier.

I can't find an article that explains in sufficient detail if this simply means white and gray-matter depth or actual differences in volume and weight

R.C.
_Remember to seriously read my signature down below and be sure you understand what I mean by it...._


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## wuliheron (Sep 5, 2011)

Its pretty meaningless anyway. What is striking about the human brain is its density rather then size and physicists have already shown that for the density we have the brain just can't get any larger because of energy constraints. The thin skin of grey matter on the outside could be compared to the billions of transistors on a computer chip and the white matter to all the other parts of the computer necessary to put that thin skin of neurons to work. We've rapidly evolved to the point of being able to cram as many neurons as possible into as small a space as possible, but the real task ahead is to improve on the architecture.


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## RobynC (Jun 10, 2011)

@wuliheron

Actually the human brain does vary from person to person. There was one guy who had a brain of around 5 pounds and he didn't have any kind of abnormal growth. I'm not saying it had a role on intellect, but there are size differences.

R.C.
_Remember to seriously read my signature down below and be sure you understand what I mean by it...._


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## wuliheron (Sep 5, 2011)

RobynC said:


> @wuliheron
> 
> Actually the human brain does vary from person to person. There was one guy who had a brain of around 5 pounds and he didn't have any kind of abnormal growth. I'm not saying it had a role on intellect, but there are size differences.
> 
> ...


In the 1970s when cat scanners first became widespread they would scan any head injury that came through the door just to build up a data base. One popular Yale Honors student came through with a "volleyball" injury and it was discovered he had 15 percent of a normal human brain. Evidently he had suffered from an undiagnosed case of encephalitis as an infant. What such cases demonstrate is that the size of the brain isn't really an issue anymore. It may have been helpful in the course of our evolution to have an oversized brain to make up for the lack of our social and cognitive development, but it looks like now more subtle architectural changes are more important.


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## RobynC (Jun 10, 2011)

@wuliheron

I didn't know of that case, but there was a case where a French civil servant had a small brain though he wasn't particularly smart, the size of his brain was so small they were amazed it would even work.


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## RobynC (Jun 10, 2011)

@_wuliheron
_


> One popular Yale Honors student came through with a "volleyball" injury and it was discovered he had 15 percent of a normal human brain.


Do you have any link to that?

R.C.
Remember, no matter how I die: It was murder; should I be tried for a criminal offense, I probably didn't do it as I'm pretty straight laced and don't even have a speeding ticket; should I mysteriously disappear -- it wasn't voluntary…


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## wuliheron (Sep 5, 2011)

RobynC said:


> @_wuliheron
> _
> Do you have any link to that?
> 
> ...


It happened back in the late 70s when cat scanners first came out and a quick Google search didn't turn up any results, but there are plenty of similar cases. It's called "neuroplasticity" or the ability of the brain and spinal cord to rewire themselves. Some scientists have been skeptical of it, but there's a growing body of evidence it is real. Lab rats that regrow their spinal cords and patients that recover from almost complete brain death. With the rapid progress being made in neurology I expect some pretty dramatic results in the near future. 

Just recently there was an announcement someone figured out how the retina sends signals down the optic nerve and that they've actually been able to make a prosthetic for blind people. It's been said the pace of neurological discoveries in recent years is just breath taking thanks in no small part to a huge array of different scanning technologies being developed.


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## Mitch Skiles (Aug 20, 2012)

The brain is also continually adapting due to neuralplasticity therefore there is not point where it has finished "developing" (and I use that term loosely)


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## 22575 (May 23, 2011)

Lord Byron had a brain mass of 2200 grams and Anatole France had a brain mass of 1100 grams suggesting that there is little difference in function in the range between these two values.* (density of brain matter is approximately that of water 1g/cc)

*information from_ The Dragons of Eden_ by Carl Sagan


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## AJ2011 (Jun 2, 2011)

wuliheron said:


> It may have been helpful in the course of our evolution to have an oversized brain to make up for the lack of our social and cognitive development, but it looks like now more subtle architectural changes are more important.


Neuroscience does seem to be going in that direction: http://www.mwcole.net/pubs/2012 Cole Journal of Neuroscience.pdf

In this paper, Cole et al. use a graph-theoretic approach for analyzing neuroimaging data to show the relationship between high fluid intelligence with high global connectivity of the prefrontal cortex to the rest of the brain. Interestingly, in their future directions, they mention Astrom and Murray, who are known for their work in adaptive and distributed control. Murray's colleague, Doyle, in this relatively recent paper:
http://www.cds.caltech.edu/~doyle/wiki/images/8/82/OnlineFinalPNASSackler2011.pdf

discusses the role of architecture in robust control theory and neuroscience. It seems interesting our analysis of complex systems has yet to catch up with the complexity of our brains conducting the analysis.


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## wuliheron (Sep 5, 2011)

AJ2011 said:


> It seems interesting our analysis of complex systems has yet to catch up with the complexity of our brains conducting the analysis.


We are using nature to study nature and Godel's theorem applies with a vengeance. Perhaps some day we'll even be able to quantify that and extend his theorem.


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## AJ2011 (Jun 2, 2011)

wuliheron said:


> We are using nature to study nature and Godel's theorem applies with a vengeance. Perhaps some day we'll even be able to quantify that and extend his theorem.


Problem with quantifying it is that we really don't know at what level of complexity nature is working at, or that there are even discrete levels. I guess as the authors imply we could assess the complexity by looking at the robustness of the system to a number of disturbances. The higher than number of different disturbances that the systems is robust to, the more complex it is. Rarely do simple systems cover a wide range of disturbances. Of course, this is all conjecture based on experience. It would be interesting to find counter-examples.


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## wuliheron (Sep 5, 2011)

AJ2011 said:


> Problem with quantifying it is that we really don't know at what level of complexity nature is working at, or that there are even discrete levels. I guess as the authors imply we could assess the complexity by looking at the robustness of the system to a number of disturbances. The higher than number of different disturbances that the systems is robust to, the more complex it is. Rarely do simple systems cover a wide range of disturbances. Of course, this is all conjecture based on experience. It would be interesting to find counter-examples.


There is a physics theory exploring the issue known as Quantum Chaos. It suggests that classical chaos emerges spontaneously from utterly random quantum interactions which eventually lead to the more orderly macroscopic world. A sort of modern twist on Democritus, but one that can be observed in the laboratory. It's a relatively new theory with little experimental evidence as yet, but if correct the theory or others like it could provide exactly the foundation required to unify all of mathematics with the observable universe.


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## AJ2011 (Jun 2, 2011)

wuliheron said:


> There is a physics theory exploring the issue known as Quantum Chaos. It suggests that classical chaos emerges spontaneously from utterly random quantum interactions which eventually lead to the more orderly macroscopic world. A sort of modern twist on Democritus, but one that can be observed in the laboratory. It's a relatively new theory with little experimental evidence as yet, but if correct the theory or others like it could provide exactly the foundation required to unify all of mathematics with the observable universe.


I just read a paper on quantum chaos by M. Berry: http://www.phy.bris.ac.uk/people/berry_mv/the_papers/Berry191.pdf

I remember reading the analysis of noise, i.e., 1/f noise, in magnetic field sensors, e.g., giant magnetoresistive (GMR) sensors. I believe some researchers related the statistics of the noise to a Poisson process (like in queuing theory) due to quantum tunneling of current through defects in the device.

The mathematics behind quantum chaos theory attempting to describe complex, macroscale emergent phenomenon is very interesting. There seems to be some truth there; we just need to know the pathway so that we could create general, testable hypotheses.

If we introduce non-locality, then an alternate viewpoint to probability arises. Non-locality may imply that information may be embedded everywhere, therefore this is a redundancy that could be exploited, i.e., everything is correlated at some level (no randomness). Could random-like statistics emerge from non-local interactions?


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## wuliheron (Sep 5, 2011)

AJ2011 said:


> I just read a paper on quantum chaos by M. Berry: http://www.phy.bris.ac.uk/people/berry_mv/the_papers/Berry191.pdf
> 
> I remember reading the analysis of noise, i.e., 1/f noise, in magnetic field sensors, e.g., giant magnetoresistive (GMR) sensors. I believe some researchers related the statistics of the noise to a Poisson process (like in queuing theory) due to quantum tunneling of current through defects in the device.
> 
> The mathematics behind quantum chaos theory attempting to describe complex, macroscale emergent phenomenon is very interesting. There seems to be some truth there; we just need to know the pathway so that we could create general, testable hypotheses.


They've already created general testable hypotheses and at this point it's more of an issue of generating enough evidence to support the theory. The most interesting evidence being explored right now has to do with macroscopic quantum effects observed in photosynthesis and some animal navigation.



AJ2011 said:


> If we introduce non-locality, then an alternate viewpoint to probability arises. Non-locality may imply that information may be embedded everywhere, therefore this is a redundancy that could be exploited, i.e., everything is correlated at some level (no randomness). Could random-like statistics emerge from non-local interactions?


Recent experiments have shown that entanglement is subject to Indeterminacy which, in turn, suggests as everything has since Bell's Theorem that quanta are simply contextual. If so then it's possible words like random and orderly have no meaning outside specific contexts. Whether the cat is perceived as dead, alive, or in superposition may just depend on the context in which you take the measurement. It's awkward and clumsy and a pain in the rear in some respects if that is the case, but it also opens the door to countless possibilities. Personally I find it a more agreeable assumption than infinite parallel dimensions or most of the other off the wall speculation on the issue.

The long term implications would mean we require an extension of the strong equivalency principle and the HUP, both of which experiments have already confirmed. We're missing some deep principle here rather than some easy to slap on metaphysical explanation.


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## AJ2011 (Jun 2, 2011)

wuliheron said:


> They've already created general testable hypotheses and at this point it's more of an issue of generating enough evidence to support the theory. The most interesting evidence being explored right now has to do with macroscopic quantum effects observed in photosynthesis and some animal navigation.


This seems very useful. Could you recommend a good review paper or book on quantum chaos? Do you apply these theories in your own work?



wuliheron said:


> Recent experiments have shown that entanglement is subject to Indeterminacy which, in turn, suggests as everything has since Bell's Theorem that quanta are simply contextual. If so then it's possible words like random and orderly have no meaning outside specific contexts. Whether the cat is perceived as dead, alive, or in superposition may just depend on the context in which you take the measurement. It's awkward and clumsy and a pain in the rear in some respects if that is the case, but it also opens the door to countless possibilities. Personally I find it a more agreeable assumption than infinite parallel dimensions or most of the other off the wall speculation on the issue.


I would like to have a better understanding of the area especially as it relates recent experiments in entanglement. What would you recommend to read?



wuliheron said:


> The long term implications would mean we require an extension of the strong equivalency principle and the HUP, both of which experiments have already confirmed. We're missing some deep principle here rather than some easy to slap on metaphysical explanation.


It's interesting to note that in any equation with an equal sign, e.g., equivalence principle, underlying the equation is a symmetry (l.h.s. = r.h.s.), e.g., in the case of the equivalence principle, inertial and gravitational mass. As theories become extended and more complex, the symmetries become more complex. Every conservation theorem leads to a symmetry. It's surprising that we've been able to find so many exploitable symmetries in such a complex world.

I agree, metaphysical explanations do not provide any utility as far as I can tell. We could partition of theories into the following (R.E. Prange, Topics in Quantum Chaos): (1) emergent, (2) submergent and (3) persistent concepts. Persistent concepts are those that exist in quantum and classical limits, e.g., phase transition in thermodynamics. Submergent concepts appear in the parent concept (quantum mechanics), but not in the classical mechanics, e.g., quantum tunneling. Emergent concepts are those that appear in the daughter theory but not in the parent, e.g., chaos. In any case, metaphysical explanations do not play a role in any of these concepts.


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## wuliheron (Sep 5, 2011)

AJ2011 said:


> This seems very useful. Could you recommend a good review paper or book on quantum chaos? Do you apply these theories in your own work?


I'm not a physicist or even a trained philosopher. Modern theoretical physics has just been a hobby of mine for 40 years related to my personal philosophy. Here is an interesting overview of the subject:

Quantum Chaos: Scientific American

And a peer reviewed explanation with more detail:

Quantum chaos - Scholarpedia




AJ2011 said:


> I would like to have a better understanding of the area especially as it relates recent experiments in entanglement. What would you recommend to read?


Quantum Biology and the Puzzle of Coherence - Technology Review

This article has a link to the original paper. The explanation the author proposes is perhaps a bit off the wall, but I find the model interesting as well as the prospect of physicists once again rediscovering the everyday world around them anew.



AJ2011 said:


> It's interesting to note that in any equation with an equal sign, e.g., equivalence principle, underlying the equation is a symmetry (l.h.s. = r.h.s.), e.g., in the case of the equivalence principle, inertial and gravitational mass. As theories become extended and more complex, the symmetries become more complex. Every conservation theorem leads to a symmetry. It's surprising that we've been able to find so many exploitable symmetries in such a complex world.


I'd say just the opposite. The human mind has obviously evolved to perceive order and the thing that has surprised and even shocked many have been discoveries like Indeterminacy which have stubbornly resisted our attempts to perceive order. Like a dog watching frozen food emerge from the microwave hot we are surprised and amazed at what we observe and, for all anyone knows, any explanation may simply be forever beyond our kin.


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