I am new with NEURON (8.0) and have some difficulties in the understanding of some structures and designs.

I use the Python (3.8) interface through the import of neuron libraries.

In particular, I begin with a soma with a given geometry and I add the Hodgkin–Huxley model for the dynamical part with the command

soma.insert('hh')

My questions are :

**: When we analyse what is behind hh.mod in the following link**

Question 1

Question 1

https://raw.githubusercontent.com/neuro ... noc/hh.mod

I do not understand the structure of the lines :

*BREAKPOINT {*

SOLVE states METHOD cnexp

gna = gnabar*m*m*m*h

ina = gna*(v - ena)

gk = gkbar*n*n*n*n

ik = gk*(v - ek)

il = gl*(v - el)

}

SOLVE states METHOD cnexp

gna = gnabar*m*m*m*h

ina = gna*(v - ena)

gk = gkbar*n*n*n*n

ik = gk*(v - ek)

il = gl*(v - el)

}

**A**-How do we introduce the rate equation for v in these lines of command ?

Do we add all currents on the right part of the equation ? And where is the left part of the equation C dv/dt ?

**B-**What is precisely the numerical method use to solve the 4 ODE’s of the HH model. Implicit, explicit, semi-implicit ? I expect that cnexp is the method but to what cnexp refers exactly ?

**C**- Can we change the method used ? e.g by an option somewhere ?

**D**- is there an hh.py version somewhere that we can use instead of hh.mod in the insert ("hh") command

**E**- If I want to change the model not using ModelDB but directly with Python is it possible ? is it possible to do it with PyNN

*http://neuralensemble.org/docs/PyNN/0.7/index.html*

**Question 2**:

In Neuron we can add some current clamp at a point of the soma by

stim = h.IClamp(soma(0.5))

**A**-How this current is added in the rate equation for v ? I do not see the way to introduce this current in hh.mod

**B**-In Neuron, soma has some extension, we can evaluate the membrane potential at a point of the membrane by soma_v.record(soma(0.5)._ref_v) (here in the middle of the soma). If I choice another point I have another profile for the membrane potential. Thus we have no space clamp, but hh.mod seems to solve ODE’s and not the PDE’s for the cable equation. Thus from where come the space here? Which equation is solved to have a space dependence of the membrane potential along the soma ?

Thanks a lot for those who have time to answer those beginners questions.