>Subject: Re: brain plasticity - what causes it?
>From: Matt Jones jonesmat at ohsu.edu>Date: Sun, 07 November 1999 02:59 PM EST
>Message-id: <804lnd$rn3$1 at fremont.ohsu.edu>
>>In article <38243B60.F9787ABC at unf.edu> John E Anderson, jander at unf.edu>writes:
>>various sorts. Some of these things must be responsible for inducing
>>plasticity -- rearrangements in the surrounding brain tissue. My
>>question is do *all* neurons produce whatever it is that induces
>>plasticity, or only some?
>>>>Taking your definition of "plasticity" (i.e., rearrangements in the
>surrounding tissue), I would guess that all neurons can cause this,
>regardless of what neurotransmitter they secrete. I say that because
>essentially every -postsynaptic- receptor known is subject to regulation
>of its density and expression on the postsynaptic membrane in a manner
>that depends on its frequency of exposure to the neurotransmitter to
>which it responds. That is, chronic exposure (or prevention of exposure)
>to acetylcholine, say, will cause postsynaptic cells to either up- or
>downregulate the density of ACh receptors they express, or sometimes
>which ACh receptor subunits are expressed, and also the location in which
>these receptors are expressed. The same holds true for glutamate, GABA,
>serotonin, dopamine, etc. So it appears that, because postsynaptic
>receptors are regulated by exposure to the neurotransmitter, every neuron
>that secretes any neurotransmitter must also have some role in guiding
>"rearangements" in the surrounding tissue.
to your excellent discussion, i'll add that what you describe is =exactly= why
'withdrawal' from addictive substances is accompanied by TD E/I(up) supersystem
the addictive substances enter into the stuff you've discussed, altering
convergence upon specific neural activation 'states', and hence, upon specific
when the addictive substances are withheld, this formerly-constructed
(literally) neural topology can only break down because of its acquired
dependence upon the artificially-induced, addictive, substance.
all instances of such 'rendering useless' (AoK, Ap8) constitute TD E/I(up)
conditions; conditions in which the supersystem is not configured optimally.
the behavioral correlates, and internal malaise, of 'withdrawal' are 'simple'
reflections of the internal TD E/I(up) [relative-randomness in the
sans-addictive-substances activation 'states'].
if folks were educated with respect to these simple realities of their nervous
system's functioning, indescriminant (non-Medical) use of drugs, if still
appropriately illegal, would, at least, be a matter of educated choice, without
folks being subjected to the augmented potential for abuse that stems from lack
of understanding, and perhaps, it would assist some addicts (such as nicotine
addicts) during their withdrawal agonies. (i don't know about substances like
'crack', cocaine, heroine, etc. it's probably the case that they so-alter the
mechanisms of 'cognition' that the addicts of such might not be able to think
the thought inherent in what you've discussed; but it'd help with respect to
cheers, Matt, ken (K. P. Collins)