Looking for Ri in the Soma equations

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1

Hello,
I am a PhD Student in France, and I worked on a neuron/synapse model that a Brian2 user has sent to me a few months ago and I wanted to determined the membrane voltage equations of the model I am using.
My issue is that my model looks like this :

Set model’s morphology

morpho = br2.Soma(10*um)
d_l = 10*um

# Set its biophysical parameters
eqs = '''
Im = gL*(EL-v) : amp/meter**2
Is = gs1*(Es-v): amp (point current)
dgs1/dt = -gs1/taus : siemens
'''

Then, when i change the value of Ri in the NeuronGroup function, the voltage has a new shape. However, I didn’t use it in my equations.

I thought that my equation would be :

dydt = (1/(Cm)).(gL.(vrest - y) + (gsmax . np.exp(-t/tauS)) . (Es - y))

But Ri seems to be somewhere in this equation.

I didn’t find it in the source files, or maybe I didn’t understand them.

Can you enlighten me on this point please ?

(If my Topic doesn’t follow the rules of this website, feel free to tell me, I will adapt it)

Thanks in advance,

Guillaume

2

Hi @gmarthe Is the morpho = br2.Soma(10*ujm) the full morphology of the model, or does it later get additional compartments? This looks a bit odd, since it is a single-compartment model, but the equations are for SpatialNeuron, which is there to support multi-compartment models. When you say that you change the value of Ri in NeuronGroup, you rather mean SpatialNeuron, right?
If this is really a single-compartment neuron simulated with SpatialNeuron, then I am indeed surprised that changing Ri makes a difference here. Your equation looks correct to me for a single compartment model, only with multiple compartments the value of Ri should come into play for calculating the diffusion current (current between compartments). Could you give some more details about what you are doing when you see changes in voltage shape?