## Equation for Single compartment models with external input

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homerobse
Posts: 3
Joined: Thu Apr 13, 2017 12:50 am

### Equation for Single compartment models with external input

Hello! I am struggling to find what exactly are the equations that NEURON integrates when I create a section with just one segment, insert hh, insert Exp2Syn and insert IClamp.

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``````soma = h.Section(name='soma')
soma2 = h.Section(name='soma2')

soma.insert('hh')
soma2.insert('hh')

syn = h.Exp2Syn(0.5, sec=soma2)
syn.e = 0
syn.tau1 = 1
syn.tau2 = 3

net_con = h.NetCon(soma(0.5)._ref_v, syn, 0, 5, 0.07)

stim = h.IClamp(soma(0.5))
stim.delay = 1
stim.dur = 5
stim.amp = 20``````
I have read many parts of Hines & Carnevale 1997 at https://www.neuron.yale.edu/neuron/stat ... /nctoc.htm), but I still don't understand how does neuron compute the voltage in the compartment including synapses and external inputs like IClamp. Is it including it at the equation 2 on the right side of the equal sign in this part of the explanation https://www.neuron.yale.edu/neuron/stat ... /nc3p1.htm ?

I mean: c dv/dt + i_ion = sum[(v_k-v_j)/r_jk] + Isyn + Iext . Is that it?

And what happens in the case of a single compartment, as the case I illustrated? Is (v_k-v_j)/r_jk=0 in this case?
ted
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Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
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### Re: Equation for Single compartment models with external inp

The discretized cable equation (Equation 2 in that paper) is the key. Currents produced by synapses and other point sources attached to a compartment, such as current or voltage clamps, are added to the right hand side of Equation 2.
what happens in the case of a single compartment . . . Is (v_k-v_j)/r_jk=0
Yes. There can be no current flow between compartments if there is only a single compartment.
homerobse
Posts: 3
Joined: Thu Apr 13, 2017 12:50 am

### Re: Equation for Single compartment models with external inp

Thank you very much!