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[Neuroscience] Re: Wherefore art thou Neuron Code?

John H. via neur-sci%40net.bio.net (by bingblat from goaway.com.au)
Sun Apr 8 11:21:30 EST 2007


"r norman" <r_s_norman from _comcast.net> wrote in message
news:so671317m0t3013efcj2p2hv29ahrosrnn from 4ax.com...
> On Wed, 4 Apr 2007 07:30:34 -0400, "Glen M. Sizemore"
> <gmsizemore2 from yahoo.com> wrote:
>
> >Damn! I wrote a rather long reply to this, and left it slightly
unfinished,
> >and during the night my computer rebooted and the document was not even
in
> >backup. Let me reply briefly, and maybe later I'll revisit the issue. The
> >modern imaging stuff (a perfect example of how neuroscience obtains new
> >facts because of physics and engineering rather than by new
> >conceptualizations) is largely a load of crap. I have always criticized
it
> >on conceptual grounds - even if the findings are accurate, and mean what
> >they re purported to mean (i.e., that part of the brain is more active)
the
> >importance of such findings is dubious. OK, such-and-such a brain area is
> >active - how does that explain the physiology of behavioral function.
> >Obviously, the fact is of potential importance, but the data are simply
used
> >to argue a version of what should be called neurophysiological animism.
> >"Look Martha! There's where the executive lives!" "And all the file
clerks
> >have to live in the hippocampus!" Now it appears that there may be little
> >reliability in the measurements - oh well, another few decades of pissing
> >into the wind.
>
> There is real value in the imaging work, but not as the "explanations"
> of behavior that are widely touted.  "Aha, when you do X then brain
> structure Y lights up.  So Y causes X!"  That is nonsense.   However
> it does strongly indicate that some specific neuronal circuits that
> are strongly associated with X are located in Y.  My main problem with
> it is that  if you see a 1 mm speck of brain tissue lighting up (and I
> am not sure that the resolution is even as good as 1 mm) then there
> are still some 1000 to 10,000 neurons possibly involved.  You will
> never even discover the enormous significance of all those other cells
> whose locations are scattered enough so that there is no significant
> change in blood patterns and oxygen usage at those locations.
>
> I get even angrier when i hear or read about the "fact" that serotonin
> is the "depression chemical" or dopamine the "addiction chemical" or
> whatever the current fashion might be.  Nobody ever says that acetyl
> choline is the "breathing chemical" even though if you block
> cholinergic junctions, you quickly die from lack of respiration.
>
> >Modularity has, no doubt some sort of verity, but what are the modules?
> >This, of course, is a version of what I mostly argue around here: unless
we
> >conceptualize behavior properly, we can never explain it at the
> >physiological level. We literally do not understand what we are trying to
> >explain! Needless to say, I think that behavior analysis has identified
the
> >core processes, and behaviorists - most notably the Big BF himself - have
> >gone far in saying how these core processes interact as complex behavior
is
> >produced. To say that this view is, ummm, a minority view, is the
> >understatement of the century.
>
> I happen to strongly believe in modularity.  It is essential when I do
> computer programming.  It is almost certainly as essential when
> evolution (or learning) does brain programming.  However the main
> point is, as you say, "we literally do not understand what we are
> trying to explain"


Just the other day I browsed through a book by Ray Kurzweill (surname not
right) wherein this AI dude argued that in his lifetime it will be possible
to upload his self into a machine and so achieve immortality. Now I read two
neuroscientists stating that we don't really have a clue about what we are
talking about.

In his text, "The Wisdom Paradox", Elkhonen Goldberg puts forward an
interesting twist on the cerebral organisation debate. He raises the
interesting idea that the right frontal neocortex is primarily about
learning new skills while the left is about executing learned skills and has
evidence to support it. Perhaps this explains why learning is so often
associated with struggle because in imaging studies one typically sees an
association between the right and sadness, the left and happiness. Tough
luck for you educators, evolution is working against you. Unless of course
you don't teach your students to learn but rather just tell them how to
think. Perhaps the best test for teaching skills will be the number of
suicides in the teacher's classes. The higher the number, the better the
teacher.

I find it much more easy to think about evolution giving rise to new
cerebral modes of function by building on the existing set rather than
creating ones anew. Yes, one can argue that over time the existing set
evolves a new module here or there but I think the analogy between the
evolution "programming" the brain and our programming of computers is deeply
misleading. Computers aren't programmmed by the environment, animals are.
Without a changing environment there would be precious little selection
pressure for new modules to arise. For example, in human evolution the
commencement of the ice ages 2.5 myr ago and the subsequent changing
environment was the primary driver of cerebral encephalisation in hominids.
Yet here the region of largest expansion is the region where we have great
difficulty assigning "modules": the frontal cortex and to a lesser extent
the temporal lobe. If evolution was about creating new modules as extensions
to existing cerebral architecture shouldn't we expect these regions to be
more precisely delineated?

I'd argue for a "connectionist modularity" rather than a "geometric
modularity". That is, these modules are not to be found in discrete
geometric regions but in how those regions are connected to other regions.
Goldberg comes up with an interesting idea here: he mentions spindle cells.
These types of cells have extensive connections and are higher in the right
than the left, very high in human beings, though recent research has
established that whales may also possess some spindle cells. Generally
though even in the primate line spindle cells are sparse. So if you're
looking for an evolutionary marker that distinguishes hominid
encephalisation than spindle cells might be worth thinking about. Then
again, the cerebellum also is a late evolver and is involved in many things
... . That's the problem with reaching back into evolution, one can imagine
too much.

The areas we see blazing up are not the executors of a behavior, the whole
organism does that. These regions possess skills that are applicable in
faciltating that behavior but we should not then assume that only that
region has these necessary skills. For some striking examples of how an old
dog can learn new tricks look up "constraint induced movement therapy". A
stunning finding using this clinical method was in a study of young girl
with cerebral palsy in Melbourne Australia. They placed under this regime in
the hope of restoring some right side function to her body. What they found
with fMRI was that it was the right motor cortex that enabled the remarkable
recovery. Now try and make sense of that terms of modules or even
neuroanatomy for that matter. The same is true of hemispherotomy,
the results are quite stunning. It also well established that with practice
cerebral regions grow, obviously invading other modules. Take my earlier
example of "action selection" centres in the mammalian brain. Any one or
number of these regions may be the prime mover of a given behavior, that
will be contingent upon the physiological, historical, and environmental
state of the organism. That is, no one region or collection of region is
necessarily the executive. Geometric modules containing specific skills for
executing behavior cannot address these issues.

At the bottom of all this is the fundamental problem of just what are
neurons, and for that matter glia, doing with all this activity. In these
days people typically think in terms of information processing. Brains
somehow analyze the environment and decide accordingly. I've often struggled
with this information processing model and in these stranger days I prefer
to think of brains as selecting behaviors rather than analyzing the
environment. This is much more concordant with evolution because that was
the primary goal of the first nervous systems. To enhance behavior not
understand the world. One problem I have with the information processing
model is that at some magical point in evolutionary history nervous systems
became interested in analyzing the environment and building internal
representations of the same as a new way to deal with the world. Some people
are fascinating by all the feedback loops in the brain and cite these as
evidence of information processing but I can think of way to approach this
problem without need to think of any information processing. Now I'll just
have to go away, be very still, and analyze that ... .



John.







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