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Hello Thomas,

thank you for your reply and sorry for my late answer. I already
performed the experiments I described here last week, but had no
time to reply until now.

> In particular, the parameters drvifall (affects the time
> constant and synaptic weight; this parameter first, because it is
> more sensitive) and drviout (affects mostly the synaptic weight)
> are adjusted until a target rate of the postsynaptic neurons is 
> reached. As these parameters can be configured only row-wise for 
> synapses, firing rates are averaged across all hardware neurons 
> during calibration. Due to this protocol, synapses are
> calibrated to generate EPSPs with comparable impact on the firing
> rates of postsynaptic neurons (i.e. area under EPSP), but not
> necessarily with comparable time constants.
Ok, so as far as I understand it the LIF parameters "w" (synaptic
weight) and "tauM" (membrane time constant with tauM = cM / gL)
influence the hidden "tauE" (excitatory synapse time constant)
parameter. That's also what some quick experiments on the hardware
showed.

So in case "tauM" and "w" stay fixed I can calculate "tauE" and
adapt the other parameters (e.g. threshold and leak potential
"eL"/"eTh") without implicitly changing "tauE". That's enough for me.

> As it is difficult to extract the synaptic time constant from the
> membrane potential, we can not provide you with numbers on how
> correlated time constants and area under EPSPs are.
Well, that turns out to be really simple: The estimation of tauE
from a membrane potential trace is a matter of few seconds. I've
simply hooked my (rather naive) Downhill-Simplex implementation onto
my high-speed single-neuron AdEx integrator and defined the RMSE
between simulated and reference membrane potential trace as cost
function. See attachment for the results.

In case you're interested: I'll publish the source code in December.

Again, thank you for your answer and best wishes from the
not-so-far-away Kirchheimbolanden,

Andreas

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