Like the Darwinists, one can't help speculating how it all happened, but
"random mutation and natural selection" just doesn't sound likely.
If all of nature is designed, I suspect one of the "designers" is the
"intelligence" contained in each molecule of living matter. At one time
life on earth consisted of one celled organisms capable of exchanging DNA.
At that point all life was related. The first multi-celled organisms were
surely the result of symbiotic relationships. At first such associations of
cells were probably plastic enough that the different body plans could
develop. Darwinists' claim that such development was the result of
"randomness" can only be the result of their determination to eliminate
teleology from nature. They have very little understanding of the process,
much less any knowledge that the process was "random". Today in mammals only
a few organs, such as the brain, may be plastic enough to change with use.
I've heard that after a few generations, the brain physiology of wild animals
held in captivity changes. A few generations after returning to the wild,
brain physiology again reverts to the wild configuration. Darwinists
chopped the tails off mice to "discredit" Lamarckism. That would have no
relevance to the question of whether the brain changes with use, and to what
degree such changes might be heritable.
Following are a couple of interesting articles:
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(1)
Here is an interesting study that suggests experience can modify brain
anatomy.
Taken from the STATS website.
http://www.stats.org
Reporting research from the Proceedings of the National Academy of Science,
the Associated Press (Mar. 15) tells us about the brains of London cabbies.
Evidently, the intensive map training all taxi operators undergo has a
neurophysiological effect. Researchers found that among cabbies, the back of
the hippocampus, the part of the brain associated with spatial memory, was
larger than it was in the comparison group. It seemed the expansion came at
the expense of the front of the hippocampus, which was smaller than normal.
Scientists do not know exactly what that part of the brain does.
(2)
New York Times
April 25, 2000
'Rewired' Ferrets Overturn Theories of
Brain Growth
By SANDRA BLAKESLEE
Like inventive electricians rewiring a house, scientists at the
Massachusetts Institute of Technology have reconfigured newborn ferret brains
so that the animals' eyes are hooked up to brain regions where hearing
normally develops. The surprising result is that the ferrets develop fully
functioning visual pathways in the auditory portions of their brains. In
other words, they see the world with brain tissue that was only thought
capable of hearing sounds. The findings, reported by Dr. Mriganka Sur and his
colleagues in the April 20 issue of Nature magazine, contradict popular
theories on how animal brains develop specialized regions for seeing,
hearing, sensing touch and, in humans, generating language and emotional
states. Many scientists claim that genes operating before birth create these
specialized regions or modules, arguing for example that the visual cortex is
destined to process vision and little else. But the ferret experiments show
that brain regions are not set in stone at birth.
Rather, they develop specialized functions based on the kind of
information flowing into them after birth. "Some scientists are going to have
a hard time believing these experiments," said Dr. Jon Kaas, a professor of
psychology at Vanderbilt University in Nashville. They demonstrate, Dr. Kaas
said, "that
the cortex can develop in all sorts of directions." "It's just waiting for
signals from the environment and will wire itself according to the input it
gets," he said. The findings may shed light on unusual brain patterns
observed in people who are born deaf or blind, he added.
"If you wanted to create a dream experiment, this would be it," said Dr.
Michael Merzenich, a neuroscientist at the University of California at San
Francisco and a leading authority on the brain's ability to change and
reorganize, a process known as plasticity. "It's about the most compelling
demonstration you could have that experience shapes the brain."
The researchers are all members or former members of the department of brain
and cognitive sciences at M.I.T. The rewiring experiments began more than 10
years ago, Dr. Sur said. He chose ferrets because their brains are very
immature at birth and undergo a late form of development that the researchers
can exploit.
As in humans, the ferret's optic and auditory nerves travel through a way
station called the thalamus before reaching areas in the higherbrain or
cortex where vision and hearing are perceived. In humans, this very basic
wiring is present at birth, but in ferrets, these important nerves grow into
the thalamus after the animal is born. Dr. Sur found that if he stopped the
auditory nerve from entering the
thalamus, the optic nerve would arrive a few days later and make a double
connection. It would go on through the thalamus and connect itself up to both
seeing and hearing regions of the cortex. The researchers then waited to see
what would happen to the hearing region of the brain once it was getting all
its signals from the retina. After a ferret or human is born, cells in the
brain's primary visual area become highly specialized for analyzing the
orientation of lines found in images or shapes. Some cells fire only in
response to vertical lines. If presented with a horizontal or slanted line,
they don't do anything. Other cells fire exclusively when a horizontal line
falls on them and yet others fire in response to lines slanted at various
angles. These specialized cells are draped across the primary visual area in
a somewhat splotchy fashion that resembles a bunch of pinwheels. The hearing
region of the brain is organized very differently, Dr. Sur said. Each cell is
connected to the next in a kind of single line. There are no pinwheel shapes.
After the rewired ferrets matured, researchers looked at the auditory region
of their brains and found that cells were organized pinwheel fashion. They
found horizontal connections between cells responding to similar
orientations. The rewired map was less orderly than the maps found in normal
visual cortex, Dr. Sur said, but looked as if it might be functional. The
researchers then asked, What does the rewired ferret experience? Does it see
or does it hear with its auditory cortex? Rewired ferrets were trained to
turn their heads one way if they heard a sound and in the other direction if
they saw a flash of light. In these experiments, one hemisphere was rewired
and the other was left normal as a control. Thus the animals could always
hear with the intact side of their brains and were deaf in the rewired side.
Not surprisingly, when the light was presented to the rewired side, the
animals responded correctly. But when connections to visual areas were
severed on the rewired side, the animals still responded to the light. It
meant that theywere seeing lights with their rewired auditory cortex, Dr. Sur
said.
The research reopens the question of what are the relative contributions of
genes and experience in building brain structure, according to Dr. Kaas.
Genes, Dr. Kaas suggests, create a basic scaffold but not much structure.
Thus, in a normal human brain, the optic nerve is an inborn scaffold
connected to the primary visual area. But it is only after images pour into
this area from the outside world that it becomes the seeing part of the
brain. All the newborn cortex knows about the outside world is from the
electrical activity of these inputs, or images that fall on the retina,
sounds that reach the inner ear or touch sensations that press on the skin,
Dr. Kaas said.
As the inputs arrive, the cells organize themselves into circuits and
functional regions. As these circuits grow larger and more complex, Dr. Kaas
said, they become less malleable and, probably with the help of changes in
neurochemistry, become stabilized. This is why a mature brain is less able to
recover from injury than a very young brain.
Young brains are astonishingly plastic, Dr. Kaas said. For example, he said,
children who suffer from a severe form of epilepsy that is treatable only by
removing one-half of their brains can learn to walk, talk, throw balls and
otherwise develop normally with only half a brain, if operated on early in
life, he said. But in recent years, scientists are also discovering that
adult brains, as well, can undergo surprising changes in response to
experience. For example, imaging experiments carried out on blind people show
that when they learn to read Braille, "visual" areas of their brains light
up. Touch seems to be residing in visual areas. Similar experiments on deaf
people show that they use the auditory cortex to read sign
language, whereas people who can hear use the visual areas of the brain for
this purpose. Dr. Sur said his laboratory was now searching for molecules
that help produce these kinds of changes in mature and developing brains. If
the chemistry of regrowth and reorganization can be understood, he said, it
would offer new avenues for helping people recover from damage caused by
strokes, accidents and various brain diseases.
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There is certainly nothing "random" about any of the brain changes described
above.
Bertvan
http://members.aol.com/bertvam
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