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Dendritic Integration (was: high resolution intracellular recordings?)

Mark Zarella zarellam at nospam.twcny.nospam.rr.com
Fri Nov 14 19:44:35 EST 2003

> The fact remains that distal EPSPs are small when they arrive at
> the soma as compared to those from more proximal sites. This
> accounts for what's called 'synaptic strengths'. From what I read,
> a synapse on the soma can result in an EPSP ~5mV high, versus
> a distal EPSP will attenuate to less than 0.5mV at the soma, ie
> 10 times. So this means synapses do have different strengths
> (though I'm not sure what's the maximum range of synaptic
> strengths). There's a theory that some kind of auto-regulation
> will result in equalization of synaptic weights because only
> those synapses that cause firing will remain in the long term.

Only those synapses that cause firing?  You don't mean alone I presume. 
  So how would this process work exactly?

> But this does not take away the fact that synaptic weights take
> a *range* of values. And that's probably the basis of memory.

The basis of memory?  How so?

> So my point is that if we look at the sub-threshold membrane
> voltage at the soma we can tell what kind of dendritic inputs
> are being recieved at a time slightly earlier.

How did you arrive at this conclusion from what you've said above?

> You can't see
> that with low sampling rates (ms range) but maybe with sub-ms
> resolution it's possible. This is clearly doable with current
> techniques but maybe no one has bothered to do that.

I'm not so sure the sampling rate is the limiting factor, but rather the 
impedances, no?

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