Neurologists think they have
it figured out pretty well: your mind is purely a by-product of your
brain; consciousness is like light produced by a light bulb, and the
light bulb is the brain itself; particular parts of the brain are
like particular parts of a computer; if one of those parts fails or
is missing, your mind is crippled just as if someone yanked out some
of the chips inside a computer.
The problem is that there a
good deal of evidence against such thinking. I've discussed some of these
items before, but let's look at some new items that have been
discussed in the news.
One interesting case recently
reported was that of a woman who has no cerebellum. The cerebellum is
known as the “little brain,” and is located near the middle of
the brain. But in terms of the percentage of brain cells found in the
cerebellum, it is misleading to say the cerebellum is the “little
brain.” According to this scientific paper, the most recent
estimates are that there are about 22 billion neurons in the cerebrum
(the outer part of the brain), and 101 billion neurons in the
cerebellum. So as the cerebellum has most of the brain's neurons, we
might expect that this woman with no cerebellum was completely
dysfunctional.
But actually, it turns out
that the woman without a cerebellum merely suffered from mild mental
retardation. She was able to walk and talk, and had even got
married and had a daughter. How could that be: losing 80% of your
brain neurons produces only mild mental retardation?
Another interesting case
recently reported is that of an 88-year old man (identified as H.W.)
who tested very well on a test of mental functioning, getting the
maximum possible score of 30. But it was found that the man had no
corpus callosum. The corpus callosum is the main part of the brain
that links the two brain hemispheres. As an article reports:
Given the importance of
the callosum for connecting the bicameral brain, you’d think this
would have had profound neuropsychological consequences for H.W. In
fact, a detailed clinical interview revealed that he’d led a
normal, independent life – first in the military and later as a
flower delivery man. Until recently, if H.W.’s testimony is to be
believed, he appeared to have suffered no significant psychological
or neurological effects of his unusual brain...Brescian and her
colleagues conducted comprehensive neuropsych tests on H.W. and on
most he excelled or performed normally. This included IQ tests,
abstract reasoning, naming tests, visual scanning, motor planning,
visual attention and auditory perception.
The same article refers us to
another case of a boy named E.B. who had surgery to remove almost the
entire left half of his brain. But he underwent rehabilitation, and
“EB's language fluency improved remarkably over the ensuing two to
three years until no language problems at all were reported at school
or in the family home.” Now how is that possible? If the light
(consciousness and intelligence) is all coming from the 100-watt
light bulb (the brain), how do you get almost 100 watts of light when
you slice the light bulb in half?
Scientists have a kind of
lame phrase to try to describe such things. They call it brain
plasticity. Brain plasticity is supposed to kind of mean: if one part
of the brain goes down, some other part will take over its work. It's
basically a kind of non-explanation rather like saying: the brain can
keep working pretty good even if you yank out most of its neurons. I
guess now we're forced to accept a doctrine of “radical brain
plasticity.”
But how can we explain such a
thing? Through Darwinian natural selection, perhaps? I can imagine
the explanation:
Through the blind process
of natural selection, humans slowly developed radical brain
plasticity, to help them survive and flourish during all those times
about 30,000 years ago when many people were losing half of their
brains because of brain surgery.
Oops, that doesn't quite
work, does it? That's because about 30,000 years ago, when humans
were shuffling around in caves, there was no brain surgery. It seems
hard to explain the origin of “radical brain plasticity” giving
any reasons relating to natural selection. From the standpoint of
survival of the fittest, nature shouldn't care about about helping
out the occasional person with a brain defect such as being born
without a cerebellum. If Darwinian evolution has 100 healthy brains
and 1 defective brain, in theory its attitude should just be: I don't
care about the deficient brain – let the fittest survive and
reproduce. That's the gist of natural selection – let the weak be
damned, and let the strong flourish. So how exactly can we account
for the origin of this “radical brain plasticity”?
It's very hard to explain
such a thing under conventional ideas that the brain is the light
bulb and consciousness is the light. Drastically different ideas may
be needed, including some new brain/consciousness model that may be
compatible with phenomena such as near-death experiences, a phenomenon
quite incompatible with the brain/light-bulb model of consciousness.
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