micro mods to neurons

COLLEEN M. SPECHT v102nq9f at ubvms.cc.buffalo.edu
Thu Oct 10 12:14:05 EST 1996


In article <325C1E16.60DF at ento.uq.edu.au>, Craig Hull <c.hull at ento.uq.edu.au> writes:
>OK, I've been following the dialogue between Ken And Colleen with some 
>interest, and have some questions. Exactly what are the physically 
>real modifications to the neural circuitry that Ken mentioned happens 
>during learning?

hi craig,

i just happend to catch this old post today.

the dialogue between Ken Collins and myself was mostly related to semantics. 
you see, when ken says 'neural changes related to learning,' for example, he
does not mean the same thing that i mean when i say it.

he speaks as if we know precisely what a memory is (neurally) when we do not. 
he thinks a mathematical model for memory means the *same thing* as neural
confirmation of *memory* when it is not.

as an example, he recently attempted to tell me that a symbol or modol of a
phenomenon is that same thing as a phenomenon. he gave a (terrific) example
that words (eg. BIG MAC) are a mathematical model of the actual, physical, big
mac.

but the words are *not* the big mac, they just represent one.  that is all
words ever do.  

in this way, he confuses a model of learning with actual learning.  LTP, which
he suggests, is a model for learning in a LIVING system.  The problem with LTP,
however, after all the excitement, is that nobody has been able to demonstrate
that LTP occurs while learning takes place NATURALLY.  therefore, LTP is a
model of learning in a living system.  BUT IT IS NOT LEARNING.

the neural engram refers to the documentation of a MEMORY in a living system. 
so far, it has not been discovered.  hopefully, someday, it will be found.  and
it will be a real memory, not a representation or model of it.

please do not let me dissuade you from looking into LTP - it is actually a
fascinating neural phenomenon but it is created in the laboratory with
relatively high electric currents that do not normally exist in a physiological
system.  this does not mean that LTP has no use; it just means it is NOT
LEARNING.

as always, weigh and consider, remember the limitations, and appreciate the
(often times very slow) process of science.

regards,

colleen specht

p.s. there is much indirect evidence for "changes" in the nervous system in
response to learning or situations where learning has taken place.  and i would
make a "theoretical" argument for peripheral memories (which have also not been
found) based on learned motor tasks.  briefly, you cannot master a piano with
just a brain (i.e. central nervous system).  the connections between your
motoneurons (to muscle tissue) are also plastic and this is probably, in part, 
how we 'learn' fine motor tasks.  And i am sure that it would not
be any more independent of the cns than the cns is of the periphery.  they are
not separate entities any more than the esophogus is of the stomach.  they just
act differently, like the latter do, although they have a common goal.

we have to remember, the distinction between cns and pns is a man made one,
even though they have many differences between them.


we also have to remember that memories are not necessarily conscious.  you
remember how to ride a bike, but you are not aware of all of the processes that
take place while you ride (i.e. when you are exhibiting that memory).

hope this helps! 

>Are they within the neurons themselves, or between 
>synapses? Have the changes been noted with electron microscopy or 
>specific markers? And more importantly, if such changes occur, are 
>they retricted to neurons within central nervous systems, or can they 
>also occur in peripheral sensory neurons? (Any references would be 
>appreciated).
>
>Cheers,
>Craig.



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