Hi Jesper,
> But then it gets tricky (in David et al. 2006). I am assuming x_0 is the
> membrane potential of the pyramidal cells, but this seems to be affected
> by 2 distinct trans-membrane currents (x_5 and x_6) with opposite
> directions. Apparently corresponding to two distinct trans-membrane
> potentials x_2 and x_3.
>
> In the text it is said that "The depolarisation of pyramidal cells
> x_0=x_2-x_3 represents a mixture of excitatory and inhibitory ...
> currents, respectively".
>
> Why is it modelled like this. I would assume there can be only 1 (mean)
> membrane potential and 1 trans-membrane current associated with a given
> population of neurons. It also seems these sources have different "decay
> times" as determined by tau_i and tau_e (aren't these related to the
> capacitance of the neurons, so how can there be two for a given
> population of neurons?)? Does this represent different neuronal
> subpopulations? Does it represent different ion-channels?
>
>
In the DCM, the pyramidal cells, in each area, are connected
reciprocally to assemblies of inhibitory and excitatory interneurons
(see Fig. 2 in David 05). So there are two inputs (mean firing rates) to
the pyr. cells. The function from the mean firing rate to the
post-synaptic membrane potential is given in Eq. 3 in David06. These two
synaptic response have different tau's and H's, depending on whether the
effect of the input on the pyr. cells is inhibitory or excitatory. The
difference of these two potentials gives the depolarization of pyr.
cells. Does this resolve it for you? :-)
> Also (maybe nitty-gritty) in David 2003 the decay of the inhibitory
> interneurons were given by tau_i, whereas in David 2006 it is given by
> tau_e?
>
tau_e (in all papers) stands for the decay rate at excitatory synapses.
Why do you think otherwise?
> I'd be immensly grateful if anyone hasn't yet left for QL and takes
> his/her time to explain this to me.
>
I wasn't even in the QL, but hope this answer still does some good.
Stefan
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