The mind is what the brain does
Most people I know believe firmly that the mind exists separately
from the brain somehow. Everyone differs in the details, but
the consensus is that there's a soul or some other nonphysical,
perhaps mystical entity. I've never seen any plausible evidence
for the truthfulness of this belief. Its only basis seems
to me to be its appeal to our imagined self-importance. What
I have seen a lot of evidence for is the idea that the mind
is a metabolic process of the brain, the way digestion is
a metabolic process of the gastrointestinal tract. When you
witness the effects of brain trauma like strokes and tumors
up close, as I have, you get a vivid demonstration of the
way that switching off or damaging parts of the brain switches
off parts of the mind. Sometimes the damage gets repaired,
and then the mind comes back. Sometimes the damage is permanent,
and the person you knew is gone forever, replaced by a different
one that bears a strong facial resemblance. Even very slight
and temporary changes to your brain chemistry, like, say,
adding a hit's worth of dissolved LSD, can produce dramatic
changes in your fundamental personhood. I
think drugs should be decriminalized, but I also think
people need to be very careful with themselves, they way they
should wear helmets on their bikes.
To me, the concept of the soul separate from the body and
its processes is an anachronism, like the belief that the
Earth is flat and that the sun revolves around it. I recognize
that it can be disturbing or even unpleasant to contemplate
the inevitable breakdown and decay of the delicate physiological
systems giving rise to your mind and personality. Materialist
thinking threatens our conventional sense of self much more
deeply than the mortality of our livers or kidneys. Most of
us in America are raised to believe in the soul, inside of
formal religious contexts or out. Any long-held belief is
difficult to let go of, especially if it challenges our wish-fulfillment
fantasies about our specialness and separateness from other
forms of life. My artist friends in particular don't like
the idea of 'reducing' their personhood to chemical reactions
and electrical discharges. To me, though, an understanding
of the brain doesn't reduce anything. For me, reading up about
the central nervous system is like hiking in New Mexico. Not
to get all Victorian on you, but the brain really is pretty
sublime.
Below is a nice diagram of the three major brain systems.
It comes from a book by Gerald Edelman called
Wider Than The Sky, which I heartily recommend in spite
of its density and occasional opacity. Edelman's hypothesis
is that the interaction between these three systems produces
your consciousness.
Here's a schematic diagram of a layer of nerve cells in the
cortex, from the Blue
Brain project.
Edelman tells us that the human brain is the most physically
complex object in the known universe. The cortex in particular
is interconnected to a breathtaking degree of intricacy. Brain
cells are constantly forming new connections (synapses) in
an endless efflorescence. Synapses that get used a lot grow
stronger over time. Less-used synapses wither and are eventually
pruned. The total number of synapses in your brain peaks at
around six to eight months of age. At this point the brain
has approximately twice as many synapses as it winds up with
by age ten. In other words, the brain starts out excessively
inter-connected, but we only keep the useful connections.
Although it was believed until recently that neurodevelopment
stopped at the end of adolescence, there's now strong evidence
that the brain develops all the way throughout adult life.
On a small scale, your cortex is wiring and re-wiring itself
in response to your every waking moment, and during dreams
as well. Edelman argues, to me convincingly, that your thoughts
and feelings consist of patterns of rapidly changing neural
connectivity. The patterns of neural activation constantly
flickering through the brain as you go about your day are
the hardware substrate for the 'software' of your mind. The
computer analogy is a good one, though limited - your computer
can't rewire itself on the fly (yet.)
The richly complex patterns of neuron activation underlying
consciousness are standing waves in the concatenated feedback
loops generated by your brain's many components and subsystems
as they signal and interact with one another. Edelman proposes
Darwinian natural selection as the organizing principle behind
the efflorescence and pruning of neural networks in the cortex.
Marvin
Minsky conceptualizes the interaction and competition
among the webs as a society of unintelligent agents, each
capable of very simple automatic information-processing. As
Daniel
Dennett puts the idea: "I have a soul, and it's made
of tiny robots." Does it seem unreasonable that a network
of dumb things could collectively produce intelligent behavior?
Read on.
Below are excerpts from a podcast called (no joke) Berkeley
Groks, an interview with Gerald Edelman conducted by Charles
Lee (in italics) on September 22, 2004.
Consciousness is one of those interesting issues in
science, but one that many think might not be amenable to
scientific inquiry. Is consciousness amenable to scientific
inquiry?
The short answer is 'Yes'. It’s true that until
recently it was the province mainly of philosophers, and
not of scientists. That situation has changed to some degree
because of technical improvements in being able to record
electrical activity in the brain in a non-invasive fashion
by various electrical tricks and thanks to physics.
I believe the evidence supports the view that the brain
is not in fact a digital computer. That the brain is in
fact something that evolution has put together in terms
of an incredible circuitry, which is capable of carrying
out pattern recognition rather than logic. Of course, it
can carry out logic in civilization after you train a person
who has higher-order consciousness [consciousness of being
conscious]. But, it’s not a logic machine first and
foremost. It’s a pattern recognition device, and it
has not been engineered - it has been developed by natural
selection.
The interesting thing is that if it’s not a computer
and it foregoes logic and a clock, then how does it manage
to keep everything together? Well, that’s what this
Theory of Neuronal Group Selection, or Neural Darwinism,
is about. It says that the brain develops incredible diversity
of its circuits during actual embryonic development and
later on in life. And secondly, it develops an arrangement
at its synapses, or the connections from one nerve cell
to another, in which these connections are strengthened
or weakened, much like there was a traffic cop on a particular
synapse saying, “You go here, and you go there.”
Now, what one has to explain is that the connectivity of
the brain is simply stunning. For example, the cortex of
the brain, that wrinkled structure you see in pictures of
the human brain, if unfolded, would be about the size of
a table napkin. It would have thirty billion neurons [nerve
cells], and one million billion connections. If you just
counted one connection per second or one synapse per second,
you would just finish counting thirty-two million years
later. If you calculate the number of possible paths, it’s
ten followed by millions of zeroes. There are ten followed
by perhaps eighty-three zeroes number of particles in the
known universe. So, it gives you respect for what evolution
can do.
This Theory of Neural Darwinism is supposed to explain
how that diversity plays in to your recognition of the world.
The brain has a huge number of repertoires of variance.
Those that match are reinforced in their synaptic connections,
and those that don’t match are diminished. Well, this
means that everybody’s brain is quite unique. No
two brains are alike, even identical twins.
Finally, there is a complex process called reentry, in
which there are massively parallel, reciprocal connections
amongst brain areas. A process of electrical stimulation
across these various areas couples the maps of the brain
together, so they all act together.
So, selection of these various neural circuits via
this process of reentry gives rise to the various conscious
experiences?
Yes. So, let’s say, what did evolution do? Well,
somewhere along the line, perhaps twenty-five million years
ago, circuitry was developed during development in which
the thalamocortical connectivity was established back and
forth in a reentrant fashion. And, what that did was
allow an animal with that brain to carry out an incredible
number of different discriminations, what you might call
'qualia'. In fact, what the philosophers call 'qualia',
the greenness of green and the redness of red, I think is
a little too constricted. I believe that qualia are all
the states you are experiencing and not experiencing now.
The qualia are those discriminations. So, effectively
speaking, the thalamocortical core, or dynamic core as we
call it, is responsible for giving rise to all these incredible
numbers of discriminations.
As you mention in your book,
can different neuronal populations give rise to the same
qualia?
Oh yes. That’s a very interesting concept called
'degeneracy', in which different structures give rise to
the same output or function. That’s really quite prominent
in all of biology, but especially in the neuronal circuits
of this dynamic thalamocortical core, in which there are
many different structural circuits that will yield the same
outcome.
So, would this imply that different structures in
different brains could give rise to the same outcome?
Absolutely, well said. It is a striking fact, and a non-trivial
one, that your brain and my brain will be unique in the
history of the universe... I make a distinction for example
between what I call primary consciousness, which is the
ability to create a scene or all these complex discriminations
in what I call “the remembered present”, right
now. And, not until you have animals that have semantic
capabilities, and in our case, true language, do you get
higher-order consciousness. If you have higher-order
consciousness, you can do what an animal that has only primary
consciousness can’t do. You can have concepts
of the past and the future, and you can develop a social
self through language. Animals are conscious, but have only
primary consciousness. Our consciousness allows us to be
conscious of being conscious.
If I show you a red bar vertically and a green bar horizontally,
and red and green lenses in your right and left eye, respectively,
then your brain can’t fuse those two discordant images. So,
what happens is first you see the red vertical, then you
see the green horizontal. You can press a button when you're
conscious of one image, the other, or neither. And, we find
that there’s a huge explosion of reentry all over
the brain when the person becomes conscious of one of those
bars.
I think there is an advance in realizing that what consciousness
gives, as a result of evolution, is the ability to make
higher order discriminations which are adaptive, and that
qualia are those discriminations. So, if you get the logic
and the science together, there would be one really fantastic
outcome that would really convince us, and that would be
if we could build a conscious artifact, if you could actually
put together with these ideas something that you could verify
is conscious. Now, the implication there is that it would
have to have some kind of language to just what I talked
about with respect to report. When that happens, some
people will be thrilled and some people will be horrified,
but I think we’ll have a confident notion that we
really begin to understand this fascinating subject.
More philosophically, how long do you think it will
be before we have such an understanding?
Oh dear. Predictions of the future are hazardous even in
science. You can be sure that sooner or later that as we
understand this subject it will come to pass, because it
has always been the case in scientific issues. I’m
working by induction here, but every time science has found
a principle, engineering has found a way to realize it.
Well, I guess we’ll just have to wait and see.
Yes, we will. You can come and visit my mausoleum.
Edelman won the Nobel Prize some years ago for his evolutionary
insights into the workings of the human immune system. Microbes
evolve much faster than humans do; their lives are short,
and their generation times are even shorter. Also, they swap
pieces of DNA among themselves, speeding the process of change
even further. The human genome hasn't
changed appreciably since the stone age, but new microbes
are popping up constantly. How do we keep pace? Edelman and
others discovered that the cells in our immune system undergo
very fast evolution by natural selection in response to microbial
invaders, without the entire organism having to die along
with them (ideally.)
The rapidness of neural population evolution is quite an
adaptive feat. Here's a remarkably recursive
paragraph from Wikipedia:
Neuronal ensembles encode information in a way somewhat
similar to the principle of Wikipedia operation - multiple
edits by many participants. Neuroscientists have discovered
that individual neurons are very noisy. For example, by
examining the activity of only a single neuron in the visual
cortex, it is very difficult to reconstruct the visual scene
that the owner of the brain is looking at. Like a single
Wikipedia participant, an individual neuron does not 'know'
everything and is likely to make mistakes. This problem
is solved by the brain having billions of neurons. Information
processing by the brain is population processing, and it
is also distributed - in many cases each neuron knows a
little bit about everything, and the more neurons participate
in a job, the more precise the information encoding. In
the distributed processing scheme, individual neurons may
exhibit neuronal noise, but the population as a whole averages
this noise out.
Edelman's theory of neural Darwinism dovetails well with
the idea of memes. I think of education and acculturation
as the building of the brain's memetic immune system, which
presumably works much like the physical one: pathogen and
antigen-specific response, lag time between exposure and maximal
response, exposure leading to immunological memory, the occasional
explosive epidemic or mass extinction of ideas. As with the
microbes, memetic evolution is happening both within and among
their human hosts. There are close analogies to be drawn between
the way brain systems communicate and the way that people
(and groups of people) communicate. Like groups of humans,
brain systems don't necessarily all get along. We like to
imagine the 'body politic' as a well-coordinated organization,
but my shrink describes it as being more like British Parliament
- everyone yelling at each other. Meditation is a highly effective
treatment for this condition. Meditation on evolution itself
is particularly helpful. Darwin
saves!
© ethan hein 2007 | back to memebase
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