brains

[Ejudy]

A few questions:

If human brains consume 18% of energy even tho they are only
2% of body, what is the energy used for? And how does this
compare to all brains in mammals and/or just in primates? Are
there specific brain activities which consume more energy
(besides keeping cool)? Does hair insulate and regulate energy
consumption related to environmental temperature in humans?

SOme brain injured people end up using different areas of
their brains more extensively than regular folks. Some even
end up out in the extremes of idiot savantism. Might some kind
of virus or disease or other injury to a brain or "group of
brains" (yeah right, you can picture the gary larsen cartoon
heheh ;-) set up a selection process of specific individual's
who may be able to bypass the injury by compensation with
development into otherwise less used functions of the brain. I
guess i am wondering about bottlenecks and frontal lobe
development kinds of situations.

It seems also very likely that humans had to do well when
presented with lots of difficult scarey situations. Some folks
are crippled to greater and lessor extents by the aftershocks
whereas in others the chemistry of the brain processes the
scarey material differently. There's a lot of new websites
talking about this cuz of the aftershocks of the world trader
center ordeal in our country. I would think children and
adults who go thru wars could benefit from lots of research in
these areas, too.

http://www.loc.gov/loc/brain/emotion/Charney.html "Another
study looked at individuals who were exposed to trauma but did
not develop PTSD. In this control population, the orbital
frontal cortex was highly activated compared to its activation
in the PTSD patients. Since the orbital frontal cortex has
inhibitory effects on the amygdala, it may be that if the
orbital frontal cortex is not being activated, and is thus not
inhibiting the amygdala, the individual is more likely to
develop PTSD."

The humans who thrived because of, or in spite of, adversity
may have had an advantage in growing their characteristically
human heavy frontal cortex, eh? Its probably a bit more
complex i'd imagine. Anybody studying stress as a factor in
the brain's evolution?

Thanx, ejudy

[Iris Bille]

"ejudy" <ejudy@my-deja.com> skrev i en meddelelse
news:46e43451.0204180833.4082496b@posting.google.com...
> A few questions:
>
> If human brains consume 18% of energy even tho they are only
> 2% of body, what is the energy used for? And how does this
> compare to all brains in mammals and/or just in primates?

For an overwiev of the brain/body ratio in humans and other
animals check out Kolb and Whishaw's Fundamentals of Human
Neuropsychology. You can't really compare the
energy-consumption of the human brain with that of other
animals, since the human brain is 'wired' differently. That is
to say, the (human) brain might not work like other mammal
brains, since it's neurons are constructed differently from
what you will see in all other animals.

> Are there specific brain activities which consume more
> energy (besides keeping cool)?

Typically the frontal cortical region uses more energy than
other cortical areas.

> SOme brain injured people end up using different areas of
> their brains more extensively than regular folks. Some even
> end up out in the extremes of idiot savantism.

Where did you get that last bit from???? (I'd really
like to know!)

> Might some kind of virus or disease or other injury to a
> brain or "group of brains" (yeah right, you can picture the
> gary larsen cartoon heheh ;-) set up a selection process of
> specific individual's who may be able to bypass the injury
> by compensation with development into otherwise less used
> functions of the brain.

That's not very likely. If you mean development of a more
'elastical' brain by means of natural selection, that is,
first of all, a proces that would take thousands of years. And
that would only work if the people with the more elastic
brains had specific advantages in the society and had higher
reproduction-rates than the rest of us. The only thing, that -
as of now - has any significance for the outcome of a
brain-injury is the extent of the injury (how much of the
brain that is damaged), and the age of the injured person (the
younger the better.). Some people tend to be better at
recovering from a brain-damage than others in their agegroup.
The reason for this lies not in these people's more elastic
brains (per se), but - apparently - in their way of living
(physical, nutritional, psychological and social parameters).

> It seems also very likely that humans had to do well when
> presented with lots of difficult scarey situations. Some
> folks are crippled to greater and lessor extents by the
> aftershocks whereas in others the chemistry of the brain
> processes the scarey material differently.

It's very different what 'breaks' a person. Some people can
survive natural disasters and war without being affected (in
any great way), while others develop post-traumatic stress
disorder after being fired from their job. It depends on their
minds, not their brains. Remember Seligman's experiments? The
subjects of neurology and traumatic experiments are dealt with
in, for example, Van der Kolk's Traumatic Stress and Yule's
Post Traumatic Stress Disorder

> "Another study looked at individuals who were exposed to
> trauma but did not develop PTSD. In this control population,
> the orbital frontal cortex was highly activated compared to
> its activation in the PTSD patients. Since the orbital
> frontal cortex has inhibitory effects on the amygdala, it
> may be that if the orbital frontal cortex is not being
> activated, and is thus not inhibiting the amygdala, the
> individual is more likely to develop PTSD."

Perhaps. This area is involved in a lot of different
activities, including empathical understanding (theory of
mind, and that sort of thing), so maybe you're just witnessing
the emotional 'flatness' of the PTSD patients.

> The humans who thrived because of, or in spite of, adversity
> may have had an advantage in growing their
> characteristically human heavy frontal cortex, eh?

Not quite sure, what you're getting at here... Please
elaborate.

Sincerely, Iris Dam

[Skeptical1]

ejudy@my-deja.com (ejudy) wrote in message
news:<46e43451.0204180833.4082496b@posting.google.com>...
> A few questions:
>
> If human brains consume 18% of energy even tho they are only
> 2% of body, what is the energy used for?

The brain is densely packed with neurons (100,000,000,000 of
them); these are complex cells each having numerous
interconnections with others (sometimes 10's of thousands of
interconnections *per* neuron); these neurons perform
electochemical processing, generating ions; this is much more
expensive per cc than what eg lungs do. Brain tissue
therefore requires large supplies of oxygen and glucose; it
is completely incapable of storing energy while at the same
time generates an enormous amount of heat. BTW, in young
children the metabolic cost of the brain is closer to 50% of
the total (Milton,
1988).

> And how does this compare to all brains in mammals and/or
> just in primates?

The relative cost of the brain depends on an animal's size,
its metabolic rate (Armstrong & Bergeron 1985) and the
specific metabolic rate of the brain tissue (Krebs 1950).
Maximizing "extra neurons" increases the evolutionary
plasticity of a species or lineage; but this increase in
total neuron number represents an increase in the metabolic
load and may be strongly selected against. The smaller the
animal the greater the relative load and the more strongly
natural selection would operate against any undue increase
(Ricklefs & Marks
1989). This gives us a predictable allometric graph for
mammals, with dolphins, chimps and humans as outliers
with larger than predicted brains.

Mammalian evolution of the brain saw the neocortex increase in
size, significance and connectedness with other regions,
especially in the case of primates culminating in chimps and
then us. Echolocating marine mammals require special
processing to integrate their echomapping and are a special
case, eg dolphins. Human brains are 3.0 times larger than
expected relative to non-human primates overall, with
neocortex at 3.2 and cerebellum 2.8. So proportions are not
much different. The human brain is NOT markedly different in
the structure one would expect from a primate brain of its
size; the density of nerve cells in the human neocortex is AS
predicted for any brain of its size; finally, it is NOT "wired
differently". It does however develop differently, especially
in the timing and degree of protein expression.

Humans pay for this huge metabolic cost via the small
intestine. Its large size in humans implies a nutrient-dense
and rapidly digested diet relative to the diets of existent
apes (Milton, 1988). This diet depends on a complex culture as
it cannot otherwise easily be obtained.

In humans there is a strategy of overproduction and loss of
neurons during development which probably buffers and
conserves heritable variation, thereby increasing evolutionary
plasticity (Finlay et al
1990). IOW cell death reduces metabolic cost but in a directed
way; we "store" this evolutionary plasticity in a new way
by means of learned culture since our "total brain" is
for metabolic reasons no longer capable of doing so and a
great part of it dies during post-natal development. The
human brain determines human culture and culture
determines the brain. They are inseperable.

> Are there specific brain activities which consume more
> energy (besides keeping cool)? Does hair insulate and
> regulate energy consumption related to environmental
> temperature in humans?

Hair on the head insulates the brain, yes. Elsewhere, *loss*
of hair permits perspiration which cools the body and thus
heated blood flowing from the brain. Loss of body hair is most
likely the result of a feedback involving neoteny and
selection for greater heat loss occurring simultaneously as
the brain grew (from approx 2 mya).

> SOme brain injured people end up using different areas of
> their brains more extensively than regular folks. Some even
> end up out in the extremes of idiot savantism. Might some
> kind of virus or disease or other injury to a brain or
> "group of brains" (yeah right, you can picture the gary
> larsen cartoon heheh ;-) set up a selection process of
> specific individual's who may be able to bypass the injury
> by compensation with development into otherwise less used
> functions of the brain. I guess i am wondering about
> bottlenecks and frontal lobe development kinds of
> situations.

The debate between modularists and their opponents is a huge
and complex issue. Sometimes an injury can be worked around
and sometimes not. In general, if a redundancy provides a
cost-effective enhancement to fitness it will be selected for,
else not. Clearly our brains include considerable redundancy.
Some amateurs have come up with this nonsense that because a
given individual can get away with a smaller brain that
therefore a larger one was not important in evolution.
Complete tosh of course. The large brain makes us what we are.

> It seems also very likely that humans had to do well when
> presented with lots of difficult scarey situations.

[snip] Remainder not my area.

Skeptical1

[Matt Giwer]

On 18 Apr 2002, ejudy wrote:

>A few questions:

>If human brains consume 18% of energy even tho they are only
>2% of body, what is the energy used for?

To think about sex.

--
Welcome to another edition of Thunderdome! -- The Iron
Webmaster, 315

[Charles]

ejudy & iris.. i have here a giant stack of brain-related
books... ummm.. here's one of the popular variety.... _The
Brain Explained_ by Daniel Drubach. On page 113, Drubach says,
"For many years it was thought that...during sleep the brain
turned itself off. today we know that this is far from the
truth; in fact, the brain consumes more oxygen and glucose
during certain stages of sleep than during wakefulness." and
on page 115, "...all mammals and birds, with the exception of
the spiny anteater, dream." He goes on to propose that the
anteater was an early brain evolution that did not use the
dream process to reduce data (a huge oversimplification on my
part there). in other words, the anteater brain was large, but
inefficient. dreaming somehow is critical in brain function &
efficiency, but we cannot yet penetrate that mystery. after an
extensive lit review, on page 117, drubach seems to prefer
this explanation. "Still another theory for the purposes of
dreams is that proposed by Jonathan Winston, who suggests that
dreaming may be necessary for the orderly processing and
storage of information that is acquired during wakefulness."
so, it appears that one thing the brain uses all that energy
for is to process and store info, and attempts to do it
efficiently. --chas

Iris Billeskov Dam wrote:

> "ejudy" <ejudy@my-deja.com> skrev i en meddelelse
> news:46e43451.0204180833.4082496b@posting.google.com...
> > A few questions:
> >
> > If human brains consume 18% of energy even tho they are
> > only 2% of body, what is the energy used for? And how does
> > this compare to all brains in mammals and/or just in
> > primates?
>
> For an overwiev of the brain/body ratio in humans and other
> animals check out Kolb and Whishaw's Fundamentals of Human
> Neuropsychology. You can't really compare the
> energy-consumption of the human brain with that of other
> animals, since the human brain is 'wired' differently. That
> is to say, the (human) brain might not work like other
> mammal brains, since it's neurons are constructed
> differently from what you will see in all other animals.
>
> > Are there specific brain activities which consume more
> > energy (besides keeping cool)?
>
> Typically the frontal cortical region uses more energy than
> other cortical areas.

snip

[Iris Bille]

[snip]
> > And how does this compare to all brains in mammals and/or
> > just in primates?
>
> The relative cost of the brain depends on an animal's size,
> its metabolic rate (Armstrong & Bergeron 1985) and the
> specific metabolic rate of the brain tissue (Krebs 1950).
> Maximizing "extra neurons" increases the evolutionary
> plasticity of a species or lineage; but this increase in
> total neuron number represents an increase in the metabolic
> load and may be strongly selected against. The smaller the
> animal the greater the relative load and the more strongly
> natural selection would operate against any undue increase
> (Ricklefs & Marks
> 1984). This gives us a predictable allometric graph for
> mammals, with dolphins, chimps and humans as outliers
> with larger than predicted brains.
>
> Mammalian evolution of the brain saw the neocortex increase
> in size, significance and connectedness with other regions,
> especially in the case of primates culminating in chimps and
> then us. Echolocating marine mammals require special
> processing to integrate their echomapping and are a special
> case, eg dolphins. Human brains are 3.0 times larger than
> expected relative to non-human primates overall, with
> neocortex at 3.2 and cerebellum 2.8. So proportions are not
> much different. The human brain is NOT markedly different in
> the structure one would expect from a primate brain of its
> size; the density of nerve cells in the human neocortex is
> AS predicted for any brain of its size; finally, it is NOT
> "wired differently". It does however develop differently,
> especially in the timing and degree of protein expression.

The human brain is actually significantly different from
other mammal brains in one respect. The neurons of the human
cerebral cortex are a lot smaller and more densly packed than
in other animal brains. In regards to brainfunction this
means that, all others being equal, the internal communcation
in the brain will work more smoothly, than it does in other
animal's brains.

[snip]

Sincerely, Iris Dam

[Ejudy]

Thanks for this

ejudy

skeptickal1@yahoo.com (Skeptical1) wrote:
> ejudy@my-deja.com (ejudy) wrote:

> > A few questions:
> >
> > If human brains consume 18% of energy even tho they are
> > only 2% of body, what is the energy used for?
>
> The brain is densely packed with neurons (100,000,000,000 of
> them); these are complex cells each having numerous
> interconnections with others (sometimes 10's of thousands of
> interconnections *per* neuron); these neurons perform
> electochemical processing, generating ions; this is much
> more expensive per cc than what eg lungs do. Brain tissue
> therefore requires large supplies of oxygen and glucose; it
> is completely incapable of storing energy while at the same
> time generates an enormous amount of heat. BTW, in young
> children the metabolic cost of the brain is closer to 50% of
> the total (Milton,
> 1988).
>
Etc.

[Ejudy]

"Iris Billeskov Dam" :
>ejudy wrote:
>
> > SOme brain injured people end up using different areas of
> > their brains more extensively than regular folks. Some
> > even end up out in the extremes of idiot savantism.
>
> Where did you get that last bit from???? (I'd really like
> to know!)
>
>
From a TV documentary on the subject of idiot savantism. I
remember they had MRI pics with colored regions showing
activity and the lack of it. The particular MRI they showed
(or maybe they showed a few)had extra dense, hot, activity
region on perifery and cold (damaged) inactive interior. This
was compared to a regular brain MRI where the activity was
spread over a much larger area and was never quite as dense
and extreme.

ejudy

[Ken Jacobs]

skeptickal1@yahoo.com (Skeptical1) wrote in message
news:<b9492359.0204191720.2c46cf46@posting.google.com>...

> The debate between modularists and their opponents is a huge
> and complex issue. Sometimes an injury can be worked around
> and sometimes not. In general, if a redundancy provides a
> cost-effective enhancement to fitness it will be selected
> for, else not. Clearly our brains include considerable
> redundancy. Some amateurs have come up with this nonsense
> that because a given individual can get away with a smaller
> brain that therefore a larger one was not important in
> evolution. Complete tosh of course. The large brain makes us
> what we are.

> Skeptical1

My own thinking in this area about the correlations of brain
weight, metabolic rate and longevity (Hofman, M. A. 1983), is
that a larger brain, allowing better durability and greater
longevity, was crucial to prehistoric/preliterate societies
maintaining cultural complexity and continuity.

Until the invention of writing, cultural continuity could only
be maintained by clear-thinking elder members of a community,
passing along their knowledge and experience. This would be
even more so if the region were sparsely-populated. So it
seems that a long-lived (redundantly big-brained) population
would be at an evolutionary advantage over an equally
intelligent but short-lived one. And that, despite the greater
resource costs involved in the former.

Parkdalian

[Ejudy]

skeptickal1@yahoo.com (Skeptical1) wrote:

>>ejudy wrote:
>
> > SOme brain injured people end up using different areas of
> > their brains more extensively than regular folks. Some
> > even end up out in the extremes of idiot savantism. Might
> > some kind of virus or disease or other injury to a brain
> > or "group of brains" (yeah right, you can picture the gary
> > larsen cartoon heheh ;-) set up a selection process of
> > specific individual's who may be able to bypass the injury
> > by compensation with development into otherwise less used
> > functions of the brain. I guess i am wondering about
> > bottlenecks and frontal lobe development kinds of
> > situations.
>
> The debate between modularists and their opponents is a huge
> and complex issue. Sometimes an injury can be worked around
> and sometimes not. In general, if a redundancy provides a
> cost-effective enhancement to fitness it will be selected
> for, else not. Clearly our brains include considerable
> redundancy. Some amateurs have come up with this nonsense
> that because a given individual can get away with a smaller
> brain that therefore a larger one was not important in
> evolution. Complete tosh of course. The large brain makes us
> what we are.
>

An excerpt from the studies being done on savantism (in later
onset dementia) and how it relates to this subject:

http://www.wisconsinmedicalsociety.org/savant/savant2000.cfm

"A Significant Discovery: New savant-like artistic and other
skills in dementia patients

A particularly intriguing recent finding regarding savant
skills is a 1998 report by Miller and coworkers who described
five patients with frontotemporal dementia (FTD) who acquired
new artistic skills with the onset of dementia of this
particular form. Consistent with characteristics and traits in
savants, the creativity in these five older, adult patients
was visual, not verbal; the images were meticulous copies that
lacked abstract or symbolic qualities; episodic memory was
preserved but semantic memory was devastated; and there was
intense, obsessive preoccupation with the art skills. Imaging
studies showed a predominance of dominant-hemisphere
(left-brain) injury consistent with the savant studies
outlined above.

The authors of this study hypothesized that selective
degeneration of the anterior temporal and orbitofrontal cortex
(particularly in the left hemisphere) decreased inhibition of
visual systems involved with perception, thereby enhancing
artistic interest and abilities. Kapur called this process
"paradoxical functional facilitation" and he speculated it is
this process which accounts for unexpected behavioral
improvement in some persons following brain injury. This would
represent a particular form of brain function compensation in
undamaged areas of the cortex and other areas and could be
part of the right brain compensatory process in savants as
well as in these five dementia patients.

In an expansion of that work, Miller and coworkers describe
seven additional such FTD patients who acquired or sustained
new visual or musical talents despite the progression of their
dementia. No Alzheimer's patient with that form of dementia
observed during the same period exhibited similar talents
(approximately 10% of patients evaluated for Alzheimer's
dementia received a diagnosis of FTD). The 12 FTD patients
with these newly emerged or sustained savant-like talents were
compared on SPECT imaging and neuropsychological testing to
FTD patients without such talent. Nine of the twelve showed
asymmetric left-sided SPECT deficits, one bilateral
abnormalities (left on MRI, right on SPECT), while two has
asymmetric right-sided dysfunction (one of whom was
left-handed). The talented group performed better on tasks
assessing right frontal lobe functions, but worse on verbal
abilities. The authors conclude "Loss of function in the left
anterior temporal lobe may lead to the 'paradoxical functional
facilitation' of artistic and musical skills. Patients with
the left-sided temporal lobe variant of FTD offer an
unexpected window into the neurological mediation of visual
and musical talents.

While the emergence of new savant skills following brain
damage from trauma or disease (acquired savantism) early in
life has been reported as noted earlier, the uncovering and
unfolding of such new savant-like skills in some older,
previously non-disabled adults, raises interesting questions
about the nature and extent of buried potential in
non-disabled individuals. The finding of predominantly left
sided damage, and the speculation about paradoxical functional
facilitation are items both very pertinent to ongoing savant
syndrome research.
============================
No model of brain function, including memory, will be complete
until it can account for, and fully incorporate, the rare but
spectacular condition of savant syndrome. In the past ten
years particularly, there have been much progress in
explaining this jarring justaposition of severe mental
impairment and prodigious mental ability. Many questions
remain unanswered, but interest in the fascinating condition
is accelerating particularly since the discovery of new savant
skills in previously non-disabled older persons with the onset
and progression of frontotemporal dementia. This finding has
far-reaching implications regarding buried potential, perhaps,
in all of us."

ejudy

[Charles]

At 11:56 PM 4/19/02 +0200, Iris Billeskov Dam wrote:
>Thank you for responding.
yes, thank you too! i had a little exposure to Danish when i
lived in St. Jan (St. John, US VI). i did genealogy work and
would get tangled up with the Danish records. Nice language,
though, and there are still people that speak Danish on all
the Virgin Islands.
>
>> ejudy & iris.. i have here a giant stack of brain-related
>> books... ummm..
>here's
>> one of the popular variety.... _The Brain Explained_ by
>> Daniel Drubach.
>On page
>> 113, Drubach says, "For many years it was thought
>> that...during sleep the
>brain
>> turned itself off. today we know that this is far from the
>> truth; in fact,
>the
>> brain consumes more oxygen and glucose during certain
>> stages of sleep than during wakefulness." and on page 115,
>> "...all mammals and birds, with the exception of the
>spiny
>> anteater, dream." He goes on to propose that the anteater
>> was an early
>brain
>> evolution that did not use the dream process to reduce data
>> (a huge oversimplification on my part there). in other
>> words, the anteater brain
>was
>> large, but inefficient.
>
>Why are you talking about the animal in the past tense? It
>still exists... Why the spiny anteater does not dream is a
>question not yet answered, but the reason probably lies in
>it's very large brain. That is to say, if dreaming is a means
>of tidying up the neuronal networks, so all the "dead ends
>and faulty wirings" can be erased, this would explain why the
>spiny anteater doesn't dream. It's brain is sufficiently
>large for the animal to make all the connections, it would
>ever need and still have plenty of room left in the brain.
>The rest of us do not have that luxury, therefore we need to
>reboot every time we sleep. (disclaimer: I am not perfectly
>sure we are talking about the same animal here, the animal I
>am refering to translates from Danish to: 'The Australian
>anteater-hedgehog' - I don't know what it is called in
>English, but it is the only mammal that does not dream, so I
>suppose we can agree on the animal in question...)

yes, i think we are talking about the same animal, the one in
Australia, related i think to the Platypus.

>
>This hypothesis, however, does not explain why babies have
>more REM sleep than older children and adults (adults spend
>appr. 20% of their sleep dreaming, babies spend 40-60%). If
>dreaming reboots the brain and thus removes all the un-needed
>connections, then babies shouldn't be dreaming tha t much...

Part of the theory is that babies are forming NEW connections,
and therefore the dreaming is actually the formation process.
(and in adults is the same process, but less of it on a daily
basis) but really we just do not know the reason at this point
in history.

>Another theory (I'm sorry, I don't give any references on
>these theories, but I don't have my books with me at the
>moment.), consideres dreaming to no more than accidental
>electrical occurences. When you dream, a group of cells in
>the formatio reticularis called raphe-nuclei, emits an
>electrical 'signal', called a PGO-wave (I believe. The p and
>o, I am certain about, but not the g), that travels from the
>pons to the occiptal cortex, where the signal is interpreted
>just as if it was something you were seeing, with your eyes.
>Through the association areas of the cortex, the signals
>recieved in the occiptal cortex, are formed into a coherent
>'story', just as with everything else, you experience.
that dreaming has NO purpose (a theory of Hobson and McCArley
and others) is not currently in favor. it seems that dreams,
whatever they do, DOES have a purpose because the brain has to
"catch up" when deprived of REM sleep. (and it also seems
likely that REM is the time when we dream).

>
>
>> dreaming somehow is critical in brain function &
>> efficiency, but we cannot yet penetrate that mystery. after
>> an extensive
>lit
>> review, on page 117, drubach seems to prefer this
>> explanation. "Still
>another
>> theory for the purposes of dreams is that proposed by
>> Jonathan Winston,
>who
>> suggests that dreaming may be necessary for the orderly
>> processing and
>storage
>> of information that is acquired during wakefulness." so, it
>> appears that one thing the brain uses all that energy for
>> is to process and store info, and attempts to do it
>> efficiently.
>
>Well, last I checked, the jury was still out on that one...
>but perhaps you're right.

no, you are right too. we don't know for sure the purpose
of dreaming.
>
>Sincerely, Iris Dam
>

love chas (reposted to srb because ejudy bounced)

[Iris Bille]

>Thank you for responding.
yes, thank you too! i had a little exposure to Danish when i
lived in St. Jan (St. John, US VI). i did genealogy work and
would get tangled up with the Danish records. Nice language,
though, and there are still people that speak Danish on all
the Virgin Islands. Can we have them back, please?? :o)
>
>> ejudy & iris.. i have here a giant stack of brain-related
>> books... ummm..
>here's one of the popular variety.... _The Brain Explained_
>by Daniel
Drubach.
>On page 113, Drubach says, "For many years it was thought
>that...during
sleep the
>brain turned itself off. today we know that this is far from
>the truth; in
fact,
>the brain consumes more oxygen and glucose during certain
>stages of sleep
than
>> during wakefulness." and on page 115, "...all mammals and
>> birds, with the exception of the
>spiny anteater, dream." He goes on to propose that the
>anteater was an
early
>brain evolution that did not use the dream process to reduce
>data (a huge
>> oversimplification on my part there). in other words, the
>> anteater brain
>was large, but inefficient.
>
>Why are you talking about the animal in the past tense? It
>still exists... Why the spiny anteater does not dream is a
>question not yet answered, but the reason probably lies in
>it's very large brain. That is to say, if dreaming is a means
>of tidying up the neuronal networks, so all the "dead ends
>and faulty wirings" can be erased, this would explain why the
>spiny anteater doesn't dream. It's brain is sufficiently
>large for the animal to make all the connections, it would
>ever need and still have plenty of room left in the brain.
>The rest of us do not have that luxury, therefore we
need
>to reboot every time we sleep.

>This hypothesis, however, does not explain why babies have
>more REM sleep than older children and adults (adults spend
>appr. 20% of their sleep dreaming, babies spend 40-60%). If
>dreaming reboots the brain and thus removes all the un-needed
>connections, then babies shouldn't be dreaming
tha
>t much...

Part of the theory is that babies are forming NEW connections,
and therefore the dreaming is actually the formation process.
(and in adults is the same process, but less of it on a daily
basis) but really we just do not know the reason at this point
in history.

This doesn't really make much sense... If babies were forming
neural connections in their sleep, there wouldn't be any means
of checking these connections against reality. Babies spend
most of the time sleeping (it might not seem that way to their
parents, though.), which leaves little time to interact with
the real world; and, according to what you've proposed, they
would have to spend most of their awake-time reality-checking
their neural networks. This would leave little or no time to
the baby's most important task: Aquiring new skills. - And if
the child doesn't learn any new skills, what should the
connections formed in it's sleep be based upon? What would
need to be established in the baby's brain?

>Another theory (I'm sorry, I don't give any references on
>these theories, but I don't have my books with me at the
>moment.), consideres dreaming to
no
>more than accidental electrical occurences. When you dream,
>a group of
cells
>in the formatio reticularis called raphe-nuclei, emits an
>electrical 'signal', called a PGO-wave (I believe. The p and
>o, I am certain about,
but
>not the g), that travels from the pons to the occiptal
>cortex, where the signal is interpreted just as if it was
>something you were seeing, with
your
>eyes. Through the association areas of the cortex, the
>signals recieved in the occiptal cortex, are formed into a
>coherent 'story', just as with everything else, you
>experience.

that dreaming has NO purpose (a theory of Hobson and McCArley
and others) (Yep, that's the names; thanks!) is not currently
in favor. it seems that dreams, whatever they do, DOES have a
purpose because the brain has to "catch up" when deprived of
REM sleep. (and it also seems likely that REM is the time when
we dream).

The theory does have an explanation for that aspect as well.
You see, the reason you sleep in the first place is because a
group of cells in the formatio reticularis called LCD-cells
stop emitting. The LCD-cells and the raphe-nuclei have a
reciprocal inhibitory effect. That means that when the
LCD-cells stop emitting, the raphe-nuclei take over, untill
they become fatigued (for want of a better word.). It follows,
that if you have gone a long time without sleeping, the
raphe-nuclei will be able to emit their signal for a longer
period of time. There aren't many studies of people who do not
dream; but those that are, conclude that dreaming is not a
necessity. The only effect deprivation of REM-sleep have is a
tendency to start having visual hallucinations (dreaming)
while awake. This seems logical, because of the PGO-waves,
that are still emitted, when the raphe-nuclei 'take over'
every time the LCD-cells become 'fatigued'.

[Iris Bille]

> > > SOme brain injured people end up using different areas
> > > of their brains more extensively than regular folks.
> > > Some even end up out in the extremes of idiot savantism.
> >
> > Where did you get that last bit from???? (I'd really like
> > to know!)
> >
> >
> From a TV documentary on the subject of idiot savantism. I
> remember they had MRI pics with colored regions showing
> activity and the lack of it. The particular MRI they showed
> (or maybe they showed a few)had extra dense, hot, activity
> region on perifery and cold (damaged) inactive interior.
> This was compared to a regular brain MRI where the activity
> was spread over a much larger area and was never quite as
> dense and extreme.

That is really interresting. Do you, by any chance, remember
the names of the scientists or perhaps the name of the
institute/hospital/university? I'm interested in
savant-abilities in relation to autistics, and I've never
found any studies, trying to establish the neural basis for
these abilities. Any help at all would be extremely welcome.

Sincerely, Iris Dam

[Ejudy]

parkdalian@yahoo.com (Ken Jacobs) wrote in message
news:<737fca24.0204210006.74ccbe1b@posting.google.com>...
> skeptickal1@yahoo.com (Skeptical1) wrote in message
> news:<b9492359.0204191720.2c46cf46@posting.google.com>...
>
> > The debate between modularists and their opponents is a
> > huge and complex issue. Sometimes an injury can be worked
> > around and sometimes not. In general, if a redundancy
> > provides a cost-effective enhancement to fitness it will
> > be selected for, else not. Clearly our brains include
> > considerable redundancy. Some amateurs have come up with
> > this nonsense that because a given individual can get away
> > with a smaller brain that therefore a larger one was not
> > important in evolution. Complete tosh of course. The large
> > brain makes us what we are.
>
>
> > Skeptical1
>
> My own thinking in this area about the correlations of brain
> weight, metabolic rate and longevity (Hofman, M. A. 1983),
> is that a larger brain, allowing better durability and
> greater longevity, was crucial to prehistoric/preliterate
> societies maintaining cultural complexity and continuity.
>
> Until the invention of writing, cultural continuity could
> only be maintained by clear-thinking elder members of a
> community, passing along their knowledge and experience.
> This would be even more so if the region were
> sparsely-populated. So it seems that a long-lived
> (redundantly big-brained) population would be at an
> evolutionary advantage over an equally intelligent but
> short-lived one. And that, despite the greater resource
> costs involved in the former.
>
> Parkdalian

Are you saying here that since the larger brain can live
longer it maybe could pass on the wisdom more effectively and
that that might have influenced the optimum number of our
brain cells? Maybe elephants are your model for this since if
the elders die there is a large negative effect on the common
knowledge of the group which influences their ability to make
it thru droughts.

Is their any possibility that certain tool production, like
for instance, creating the basic hand ax, might have had the
function of pushing a certain kind of brain development and
establishing it within hominids each generation
environmentally which may have influenced other kinds of
mental reasoning? In the developmental stages of children, if
they miss certain developmental stages everyone gets worried.
So they are supposed to be doing certain manipulation
activities at certain times. If babies hear language early on
then they can speak when it comes time. If they are deaf they
miss out and their brains don't get set to become verbal. Are
there material cultural skills which might have this same
effect that maybe we might see evidence of? I would think
perhaps there would be an interesting feedback system with our
brains you could chart somewhat thru hominid development which
might only come about thru these types of cultural traditions.

ejudy

[Skeptical1]

"Iris Billeskov Dam" <iris_dam@post.tele.dk> wrote in message
news:<a9rha4$2qk7$1@news.cybercity.dk>...
> [snip]

> The human brain is actually significantly different from
> other mammal brains in one respect. The neurons of the human
> cerebral cortex are a lot smaller and more densly packed
> than in other animal brains. In regards to brainfunction
> this means that, all others being equal, the internal
> communcation in the brain will work more smoothly, than it
> does in other animal's brains.

Could you give me a citation for this, please? I'd need the
research paper (not textbook), so that I can follow through
subsequent citations.

Surely one needs to be very careful here about how one does
the scaling? I'd been reading up on the relatively new
universal scaling law for gray/white matter just recently. As
I understand it, consistent phylogenetic scaling relationships
(relative to grey matter) have already been established for
neuron density, total convoluted surface area and white matter
volume, and to a degree also for neuron number(?), neocortex
thickness and soma radius. These consistent scales apply to
all mammal species including humans.

Also, having done quite a bit of reading on "spindle neurons"
and the like, I've noticed how very complex is the issue of
individual neuron count and especially neuron size. Almost all
papers that I've read prefer to stick to volume or other
measures of "mass".

To give others who may be interested a bit more background on
the scaling laws: In the mammalian cortex in general, the
number of neurons per unit volume (ie neuron density) declines
with increases in brain size in a constant way (Macphail).
However, as neuron density declines with increasing brain
size, so too does neural connectivity increase. The volume of
the neocortical gray matter is a linear function of brain
volume, whereas the mass of interconnections forming the
underlying white matter increases disproportionaly with brain
size. The volumes of cortical gray matter and the adjacent
white matter are closely related by a power law across nearly
the full range of mammalian brain sizes: the gray matter
volume is proportional to the cube of the average fiber length
in the white matter.

These findings are corroborated by sound reasons of
neurophysiological efficiency: the amount of white matter
needed to interconnect the neocortex must follow a power law
if cortical uniformity and compact wiring are assumed. All
mammal brains, and not merely human ones, operate at maximal
efficiency for their size; one hundred million years of
evolution has seen to this.

According to Dean Falk, "the evolutionary process of
neocorticalization in primates is mainly due to the
progressive expansion of the mass of interconnecting nerve
fibers, rather than to the increase in the number of cortical
neurons (Hofman, 1989; 2000). The high correlation between
both variables ensures that the mathematical model, describing
the relationship between brain size and white matter volume,
can be used for predictive purposes to estimate the mass of
myelinated nerve fibers for a hypothetical primate."

As I understand it, humans fit nicely into the above scaling
and all is peachy. How we don't fit in is that our brain is 3
times larger than expected for a primate of our body weight
and metabolism, and therefore 7 times larger than expected for
a mammal. The additional metabolic cost should therefore be
easy enough to calculate.

Skeptical1

[Firstjois]

I know absolutely nothing about this subject but in good old
SAP tradition I will not let that stop me from jumping right
in: Quote from previous post:

This doesn't really make much sense... If babies were forming
neural connections in their sleep, there wouldn't be any means
of checking these connections against reality. Babies spend
most of the time sleeping (it might not seem that way to their
parents, though.), which leaves little time to interact with
the real world; and, according to what you've proposed, they
would have to spend most of their awake-time reality-checking
their neural networks. This would leave little or no time to
the baby's most important task: Aquiring new skills. - And if
the child doesn't learn any new skills, what should the
connections formed in it's sleep be based upon? What would
need to be established in the baby's brain?

End of quote:

I would think that every sound needs to be evaluated, every
movement needs to be practiced, logged and catalogued. I love
to see a baby examining its hands and feet. Taste, touch,
maybe smell them too. Eye contact, faces, smiles, and every
other thing that becomes automatic to us eventually must be
examined and if forming neural connections in their sleep is
how they get these sights, sounds, and smells into somekind of
order that's okay with me.

Jois

[Charles]

Iris Billeskov Dam wrote:

> >Thank you for responding.
> yes, thank you too! i had a little exposure to Danish when i
> lived in St. Jan (St. John, US VI). i did genealogy work and
> would get tangled up with the Danish records. Nice language,
> though, and there are still people that speak Danish on all
> the Virgin Islands. Can we have them back, please?? :o)
> >

we did buy those islands at a good price. thanks! they are
lovely beyond any place i have ever experienced. and its
the only place i know of in America that we drive on the
left. {snips}

> The theory does have an explanation for that aspect as well.
> You see, the reason you sleep in the first place is because
> a group of cells in the formatio reticularis called
> LCD-cells stop emitting. The LCD-cells and the raphe-nuclei
> have a reciprocal inhibitory effect. That means that when
> the LCD-cells stop emitting, the raphe-nuclei take over,
> untill they become fatigued (for want of a better word.). It
> follows, that if you have gone a long time without sleeping,
> the raphe-nuclei will be able to emit their signal for a
> longer period of time. There aren't many studies of people
> who do not dream; but those that are, conclude that dreaming
> is not a necessity. The only effect deprivation of REM-sleep
> have is a tendency to start having visual hallucinations
> (dreaming) while awake. This seems logical, because of the
> PGO-waves, that are still emitted, when the raphe-nuclei
> 'take over' every time the LCD-cells become 'fatigued'.

I have never heard of a study that says there are people that
do not dream. the studies I have seen... all of them.... say
that everybody dreams. I am looking at one cat-study that
"supressed" the raphe nuclei area and the cat therefore acted
out the dream. the cat seems to dream of attacking, defending
types of behaviour. Do we, science that is, really know why we
sleep? certainly there is a "regeneration" effect, but that
has been proved to be too simple. especially considering the
increased use of glucose and oxygen during REM. I think there
are many mysteries yet to be discovered, and this is a
wonderful subject. luv, chas

[Ejudy]

"Iris Billeskov Dam" wrote:

> That is really interresting. Do you, by any chance, remember
> the names of the scientists or perhaps the name of the
> institute/hospital/university? I'm interested in
> savant-abilities in relation to autistics, and I've never
> found any studies, trying to establish the neural basis for
> these abilities. Any help at all would be extremely welcome.
>
> Sincerely, Iris Dam

I looked and found nothing. It may have been that the show was
on the brain and this was simply a section of the show. If you
remember the savant person who would ride a bus downtown then
could come home and draw exquisite almost infinitely detailed
drawings of the cityscape as if using a form of photographic
visual memory, i think that person was featured on the show
too. I have a visual memory of the show ;-) so i remember the
drawings.. And it was in the late '80s probably. Probably PBS.

Another thing about dreams, i knew a person who had a
tryptophan problem and was exhausted by extreme detailed
memories of her dreams. These encroached upon her waking life
and caused her great and fascinating pain. She related one of
her dreams and the detailing wiped out most of the useful
possibilities of the dream as a metaphorical story or
experience. There wasn't any trimming and editing in her
memory and it was much less interesting as what we think of
as a dream and more like a processing of a jumble of
experience. She could remember hours of details. This lady
was put on some different medicines till they relieved her of
the forceful intrusion of recounting the dreams and so she
was able then to get a restful night of sleep and do better
with her daytime work. I think she was a biology student or
something in the sciences.

ejudy

[Ejudy]

skeptickal1@yahoo.com (Skeptical1) wrote:
>
> According to Dean Falk, "the evolutionary process of
> neocorticalization in primates is mainly due to the
> progressive expansion of the mass of interconnecting nerve
> fibers, rather than to the increase in the number of
> cortical neurons (Hofman, 1989; 2000). The high correlation
> between both variables ensures that the mathematical model,
> describing the relationship between brain size and white
> matter volume, can be used for predictive purposes to
> estimate the mass of myelinated nerve fibers for a
> hypothetical primate."
>
> As I understand it, humans fit nicely into the above scaling
> and all is peachy. How we don't fit in is that our brain is
> 3 times larger than expected for a primate of our body
> weight and metabolism, and therefore 7 times larger than
> expected for a mammal. The additional metabolic cost should
> therefore be easy enough to calculate.
>
> Skeptical1

WHen do we make the interconnecting fibers? Is that the deal
where there are too many to begin with and then the unused
ones attrophy or are discarded? I don't have anything to look
at and i am trying to remember so sorry if i have gotten this
wrong. If this is how they are "retained" might that mean the
bigger the brain the better to start with cause its like a
trimming and refining process?

ejudy

[Iris Bille]

[snip]
> Could you give me a citation for this, please? I'd need the
> research paper (not textbook), so that I can follow through
> subsequent citations.
[snip]

I can't give you the citation at the moment. I do not have my
books with me, but I'll be able to look into it in a week or
so from now. The only place where I, at the moment, can
remember reading about it is in an article by Nielsen from
Psyke & Logos (1996, I believe), but unless you understand
Danish... :o[ I'll try to look it up in my books, or ask
Nielsen about it.

Sincerely, Iris Dam

[Ejudy]

"Iris Billeskov Dam" <iris_dam@post.tele.dk> wrote:

> That is really interresting. Do you, by any chance, remember
> the names of the scientists or perhaps the name of the
> institute/hospital/university? I'm interested in
> savant-abilities in relation to autistics, and I've never
> found any studies, trying to establish the neural basis for
> these abilities. Any help at all would be extremely welcome.
>
> Sincerely, Iris Dam

Here's a good link that will lead you farther i believe.

http://www.wisconsinmedicalsociety.org/savant/savantsyndrome.-
cfm

I met a young man my son's age last year who is both
autistic and specifically gifted in a certain math area. He
kept following my son around for hours and my son was
getting all nervous. He said he knew "who" my son was and
that he "knew" about him. My son was really confused. We
talked to his mom who told my son some subject to connect
with her son on and they ended up having an amazing
intensity of connected conversation for the few next hours
completely in a world of their own on this one subject. My
son is not autistic but he has some very unussual skills.
Her son had a dramatic specific gift. It was a very
interesting interaction. Her son barely notices anyone. My
son has some unnusual math/science verbal stuff but its
spread alot wider. The intensity of this interaction didn't
seem like what i think of as children's minds.

ejudy

[Charles]

to bring it all home to sap, then, the infant brain leaves the
uterus in a partially formed condition.... because of
selection, diet, increasing brain size, decreasing gestation,
increasing childhood, maternal pelvic size,etc., and the
dreaming is necessary, in some unknown way, to form nueral
pathways. (although an alternate theory is that instead of
pathway formation... actual brain connectivity... the dreaming
is to eliminate junk sensory material...not as likely IMHO
because of, as Iris pointed out, the infant has not yet had
any experinces to process.) I assume that dreaming DOES have a
purpose, but that purpose is still obscure. I think the
process of dreaming is THE method the brain uses to organize
itself. and by "organizing" it is also actually forming
physical connectivity, across the synapse anyway, between
dendrites and axons. that is why infants have to spend so much
time in REM sleep. and we as adults process, organize, digest
if you will, the days data thru dreaming. it's natures method
of creating a big brain in a small body..to be born earlier.
we practice it all every night. so life is a great big
rehearsal. <g> thank my lucky stars for reproduction! --chas

firstjois wrote:

> I know absolutely nothing about this subject but in good old
> SAP tradition I will not let that stop me from jumping right
> in: Quote from previous post:
>
> This doesn't really make much sense... If babies were
> forming neural connections in their sleep, there wouldn't be
> any means of checking these connections against reality.
> Babies spend most of the time sleeping (it might not seem
> that way to their parents, though.), which leaves little
> time to interact with the real world; and, according to what
> you've proposed, they would have to spend most of their
> awake-time reality-checking their neural networks. This
> would leave little or no time to the baby's most important
> task: Aquiring new skills. - And if the child doesn't learn
> any new skills, what should the connections formed in it's
> sleep be based upon? What would need to be established in
> the baby's brain?
>
> End of quote:
>
> I would think that every sound needs to be evaluated, every
> movement needs to be practiced, logged and catalogued. I
> love to see a baby examining its hands and feet. Taste,
> touch, maybe smell them too. Eye contact, faces, smiles, and
> every other thing that becomes automatic to us eventually
> must be examined and if forming neural connections in their
> sleep is how they get these sights, sounds, and smells into
> somekind of order that's okay with me.
>
> Jois

[Iris Bille]

[snip]
> I have never heard of a study that says there are people
> that do not
dream. the
> studies I have seen... all of them.... say that
> everybody dreams.

That's right, everybody dreams. The people I was referring to,
had all experienced brain damage (in form of a tumor or a
trauma) to either the limbic system or the formatio
reticularis.

> I am looking at one cat-study that "supressed" the raphe
> nuclei area
and the
> cat therefore acted out the dream. the cat seems to dream of
> attacking, defending types of behaviour.

Yeah, I've read that study too. The scientists bypassed one of
the normal function of sleeping (that is cutting off the
connection between the brain and the body) to see whether the
cats acted in a coherent way according to whatever they might
have been dreaming. The study was, interestingly enough, also
used to deliver one of the deathblows to freudian dreamtheory
since none of the cats displayed any sexual behavior. (The
freudians retaliated by saying that you can't compare cats and
humans, since cats don't have any ego or superego... )

> Do we, science that is, really know why we sleep?
> certainly there is
a
> "regeneration" effect, but that has been proved to be
> too simple.
especially
> considering the increased use of glucose and oxygen during
> REM. I think there are many mysteries yet to be discovered,
> and this is a wonderful subject.

Again, you're absolutely right. No one knows for sure, what
the reason for sleeping is. Most likely we sleep because the
body needs to restore itself. And because it is not
'cost-efficient' for an animal to be awake all the time; the
animal would have to spend twice as long looking for food,
without any real benefits. Humans, for instance, would be a
menace to themselves if they were to be awake at night. We
can't see in the dark, therefore we would have a lot more
trouble finding food; and besides we would be at the mercy of
the nocturnal predators.

Sincerely, Iris Dam

[Iris Bille]

Well, thank you for trying, anyway.

Best regards, Iris Dam

>
> I looked and found nothing. It may have been that the show
> was on the brain and this was simply a section of the show.
> If you remember the savant person who would ride a bus
> downtown then could come home and draw exquisite almost
> infinitely detailed drawings of the cityscape as if using a
> form of photographic visual memory, i think that person was
> featured on the show too. I have a visual memory of the show
> ;-) so i remember the drawings.. And it was in the late '80s
> probably. Probably PBS.
>
> Another thing about dreams, i knew a person who had a
> tryptophan problem and was exhausted by extreme detailed
> memories of her dreams. These encroached upon her waking
> life and caused her great and fascinating pain. She related
> one of her dreams and the detailing wiped out most of the
> useful possibilities of the dream as a metaphorical story or
> experience. There wasn't any trimming and editing in her
> memory and it was much less interesting as what we think of
> as a dream and more like a processing of a jumble of
> experience. She could remember hours of details. This lady
> was put on some different medicines till they relieved her
> of the forceful intrusion of recounting the dreams and so
> she was able then to get a restful night of sleep and do
> better with her daytime work. I think she was a biology
> student or something in the sciences.
>
> ejudy

[Skeptical1]

ejudy@my-deja.com (ejudy) wrote in message
news:<46e43451.0204220724.732978c9@posting.google.com>...

> WHen do we make the interconnecting fibers? Is that the deal
> where there are too many to begin with and then the unused
> ones attrophy or are discarded? I don't have anything to
> look at and i am trying to remember so sorry if i have
> gotten this wrong. If this is how they are "retained" might
> that mean the bigger the brain the better to start with
> cause its like a trimming and refining process?

It's primarily the neurons that die off. We start with about
double what we need. This link may help. It's the tutorials at
the Society for Neuroscience. Scan down the page for
"Development". http://www.sfn.org/Template.cfm?Section=BrainB-
riefings&NavMenuID=231

Skeptical1

[Ejudy]

"Iris Billeskov Dam" <iris_dam@post.tele.dk> wrote:

> Well, thank you for trying, anyway.
>
> Best regards, Iris Dam
>
>

Here are some excerpts for you :

http://www.wisconsinmedicalsociety.org/savant/savant2000.cfm

A plausible hypothesis

While no single theory or construct can as yet explain all
savants, in my view, based on observations and studies to
date, a plausible explanation for many cases of savant
syndrome can be summarized thus: In the savant, there is
disruption of typical left hemisphere functions as a result of
prenatal influences, sometimes sex linked (testosterone), or
prenatal or subsequent CNS injury, even later in life, which,
in turn, leads to a compensatory migration of neurons and
dominance of right hemisphere function. A predilection for
simultaneous, non symbolic, literal skills and functions
results. Such left hemisphere cortical and/or corpus callosum
abnormality is coupled with damage to the higher level
cortico-limbic (cognitive) memory circuits, probably arising
from those same influences, causing the savant to rely upon
and largely be limited to more primitive, lower level
cortico-striatal (habit) memory circuits. These cortical and
memory circuit injuries together produce the savant's
characteristic cluster of symptoms, capabilities, and unique
memory. In talented savants, concreteness and impaired ability
to think abstractly are locked in a very narrow band but with
constant repetition and practice, the savant is able to
produce sufficient coding so that access to some unconscious
algorithms can be automatically attained. In the prodigious
savant some genetic factors may be operative as well, since
practice alone cannot account for access to the vast rules and
syntax of music, art or mathematics which is innate to these
individuals. Once established, intense concentration,
practice, compensatory drives and reinforcement, from family,
therapists and caretakers, play important roles in further
developing and polishing the extraordinary mix of skill and
memory made possible by the unique and idiosyncratic brain
functioning.

In 1995 Young carried out the largest study on savants (51
persons) in which, in addition to obtaining family histories,
each savant was interviewed and given standardized
psychological and neuropsychological tests. She concluded,
based on this single largest sample studied in a uniform
manner, that the savant is a neurologically impaired
individual who shows language and intellectual impairments
consistent with autism. Skills are generally rule based,
rigid, and highly structured lacking critical aspects of
creativity and cognitive flexibility. Preserved neurological
capacity to process information related to their skills, a
well developed declarative memory, a familial predisposition
toward high achievement and support, plus the opportunities
for encouragement and support provide a climate for savant
skills to develop. In a more recent summary of that work Young
and Nettelbeck conclude that literal rote memory alone does
not provide a basis for savant skills, not do they represent
"separate intelligences" outside the concept of overall
general intelligence.

These findings regarding the idiosyncratic cortical and memory
circuitry in the savant are supportive of consistent with the
cortical damage/memory impairment theories above. Instead of a
"pathology of superiority" based on brain areas that are
damaged and compensated for elsewhere, Young and Nettlebeck
propose that brain areas that are spared are most crucial in
accounting for the special skills of savants, rather than the
savant relying on brain areas that have compensated for damage
elsewhere.

=============================
Left brain injury and right brain compensation

One theory that consistently provides an increasingly
plausible explanation for savant abilities in many cases is
left brain injury with right brain compensation. In 1980 Brink
presented a case of a normal 9 year old boy who was left mute,
deaf and paralyzed by a gunshot wound to the left hemisphere.
Following that injury, unusual savant-like (acquired savant)
mechanical skill emerged, presumably from the undamaged right
hemisphere. Tanguay pointed out that the skills most often
seen in autisic savants are those associated with right
hemisphere functions, and the skills most lacking tend to be
associated with the left hemisphere. Rimland also highlighted
the simultaneous nature of right brain activities in contrast
to the sequential nature of left brain activities in the
autistic savant. A number of cases have been reported with
documented left hemisphere damage on imaging studies such as
CAT scans, correlated with corresponding findings on
neuropsychological testing.

Even before CAT scans and MRI techniques were available, as
early as 1975, pneumoencephalograms demonstrated left
hemisphere abnormalities, particularly in the temporal lobe
areas, in 15 of 17 autistic patients, four of whom had savant
skills in music or mechanical abilities. A 1999 PET study
showed low serotonin synthesis in the left hemisphere of
persons with autistic disorder and neuropsychological tests
also confirmed left hemisphere deficits in these individuals.
Other more recent studies will be outlined in more detail
below. The observation that most savant skills and abilities
are of a type and nature associated with right brain capacity
is consistent with such left brain damage and right brain
compensation.

================================
http://www.wisconsinmedicalsociety.org/savant/faq.cfm#8

In summary, Autistic Disorder appears in fact to be a group of
disorders, one sub-group of which is Early Infantile Autism as
originally described by Dr. Kanner. Onset can be from birth,
or symptoms can occur after a period of normal development.
The etiology is organic, not psychologic, and the causes are
apparently several, rather than a single one. Within Autistic
Disorder as many as 10% of such individuals have savant
syndrome. However savant syndrome can also occur in conditions
other than Autistic Disorder, although not as frequently.
Therefore not all autistic persons are savants, and not all
savants are autistic.
=========================
Such left brain damage/right brain compensation, coupled with
semantic memory damage and procedural memory compensation,
produces, then, the emergence of right brain skills coupled
with automatic memory typically and characteristically seen in
savant syndrome.
=======================
"....while each of us have as well many right brain
capabilities (non-symbolic, artistic, concrete, directly
perceived) we live in a world that rewards left brain
strengths (sequential, logical, and symbolic including
language specialization). Thus we have generally come to rely
on the well-worn circuits of left brain function + semantic
memory, to the exclusion or relative disuse of right brain
function + habit memory. But when those well worn circuits
are disturbed by head injury or CNS disease, for example, the
more primitive, lower level circuits of right brain/habit
memory do come to the fore. Some refer to that in brain
injury and disease as a compensatory phenomenon called
"paradoxical facilitation". But is actual brain injury or
disease necessary in order to tap some of that buried
potential, or might there be other methods short of injury or
disease itself to bring us in touch with more buried skills
and memory function? Could specific cognitive techniques or
other procedures facilitate such a process in all of us? Some
investigators are using large magnetic circuits (rTMS) to
temporarily disable brain function in certain areas in
non-disabled persons to see if these more primitive, buried
circuits can emerge in 'normal' persons.

ejudy