Hi all,

I have a simple passive cable model of dendrite. I used the codes of extracellular record and stim with a monopolar electrode. I put the electrode far from the end of the cable. I mean the cable is horizontal with the length of 500um, and the electrode location is (6000,0,0) , so I have a uniform electric filed, and field lines are parallel to cable. In simulation plot I see the electric field (-dvext/dx) is negative but in theory and based on coulomb law, vext is (I rho / 4 PI r) and in this case r is equal to x which is negative for all points of the cable , so vext is negative for a positive current, and dvext/dx is (-I rho / 4 PI x^2), so electric field is positive which is in contrary with the simulation results. Would you please help me find the problem?

And also another question, in space plot of vm at the end and start of the cable dvm/dx is zero. I guess it is because of sealed end boundary conditions, but this condition tells dvi/dx is zero, not dvm/dx! Where is the problem?

Thanks