Synaptic modification rules ?

Matthew Kirkcaldie m.kirkcaldie at removethis.unsw.edu.au
Tue May 18 23:06:57 EST 2004


In article <DeAqc.50527$325.1090290 at news20.bellglobal.com>,
 "NMF" <nm_fournier at ns.sympatico.ca> wrote:

> So the process you have mentioned suggests that the temporal coding of BAP
> and EPSP has been likened to the important coincidence detector that Hebb
> remarked in his work.  The spike-dependent (Hebbian plasticity) process is
> considered important for producing long lasting changes in synaptic
> potentation.  Moreover, due to the rather compartmentalized aspect of the
> dendritic tree (i.e. branches, necks, spines, and complex geometry of
> dendrites), one would find the potential for many different local
> coincidence detection mechanisms, i.e. the NMDA receptor, itself, or even
> the ryanodine-sensitive internal stores might all serve as coincidence
> detection apparatus.

Neil, sounds like you have also read (or ought to read) the work of Greg 
Stuart and Michael Hausser regarding the immense complexity of synaptic 
inputs filtering through a dendritic tree.  Not only do large changes in 
membrane capacitance cause great variation in EPSP (more distal = larger 
in general, for a given current), but the generation of sodium and 
calcium spikes which are actively propagated is a very strong 
coincidence detection mechanism, although the coincidence would need to 
be between two inputs rather than a pre and postsynaptic cell.  Of 
course the BAP gets into this melee as well.  I love telling students 
this stuff when they think they have neuron basics down pat.  Then when 
they get comfortable there, I hit them with glial interactions.  I 
always say, if it seems straightforward, you haven't understood the 
problem!

      Cheers,

         Matthew.



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