encephalogram database

mat mats_trash at hotmail.com
Mon Feb 4 04:59:33 EST 2002


> For many purposes, instrumentation can treat one impulse as
> indistinguishable from another.  They're both versions of the
> theoretically perfect Dirac impulse.  But to understand the variations
> in what makes one impulse different from another, you have to look
> at small differences among them.  You mentioned pulse width as one,
> but there are infinitely many frequencies in a real, imperfect, impulse.
> For example, the incoming pulses from one set of dendrites may
> cause a slightly different response than another set of dendrites.  The
> timing of incoming pulses can sum, or interfere, in different ways.  So
> its not just a question of whether the output impulse is there, but
> what characteristics that impulse has, which might convey information
> about how the impulse was generated in the first place.

Do you simply mean sampling at a higher frequency to get data of
higher resolution?

> 
> Secondly, there is no reason to assume that the NTs crossing
> the synaptic gap all have the same conformation.  Yet identifying
> possibly varying conformations is difficult, perhaps impossible
> at this point in technology, since the conformation can change
> as you measure it.  That leaves the electrical signature of one
> impulse versus another as the most likely way to distinguish
> messages, assuming that they exist at all.  Although the NTs
> may be stored up for hours before an impulse is generated,
> conformation might change as charge distributions change.
> Also, the DNA/RNA bases might carry different charges
> that are more dynamic, reflecting message content.  Or
> maybe not; its just a thought worth looking into.

What do you mean by conformation? Most of the major NTs are nothing
more than single amino acids and variations thereon.  There's not much
to play with to use different 'conformations'.  Are you suggesting
that say glutamate in different conformations binds to different
receptors (or to the same receptors with differing affinity)?

I don't get the bit of DNA/RNA... are you suggesting that they are
transmitters or that the charge on the bases (??) affects the protein
synthesised? and that membrane potetnial affects these charges and
subsequently alters protein product?

> 
> So I'm not suggesting very high frequencies for some mystical
> reason, but as a way of distinguishing among very subtle differences
> in the impulses as a way to shed further light on whether the
> impulses themselves convey messages other than the simple
> event of an impulse occurrence.

Different trasnmitters (and theis respective receptors) induce
differing post-synaptic currents/potentials (and much work has already
been done on it) and these summed in different ways to alter the
probablility of firing an action potential.  Further it would be very
intersting to elucidate how different synpatic events alter things
such as gene transcription and protein synthesis (but again, a lot of
work has been done on this already notably by Kandel)




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