How big nseg is enough?

[thats_karlo]

Hi,

I made a model that contains 3-section.and outputs of code are

injected current, maximum amplitude of total ionic current in soma, maximum level of soma.v(0.5) during current injection

for these code, i used dt=0.002 and second number:

for (x,0) totalarea +=area(x)
Itotal=(I_ionic+I_leak)*totalarea/100

run2() is my "proc" to run code. the result is

Code: Select all

oc>forall nseg=3
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=0.36043425   max(soma.v(0.5))=-43.519452

oc>forall nseg=7
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=0.67812746   max(soma.v(0.5))=-43.679981


oc>forall nseg=15
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=1.0150751   max(soma.v(0.5))=-43.705834


oc>forall nseg=19
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=1.3440978   max(soma.v(0.5))=-43.708511



oc>forall nseg=23
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=1.3530679  max(soma.v(0.5))=-43.709914


oc>forall nseg=27
oc>run2(-0.0897)

Iinj= -0.0897     abs(Itotal)=1.6832776   max(soma.v(0.5))=-43.710741

d_lambda, method , creates nseg=1,3,13 for 3-sections.
I define nseg value before define channel density.

I expect, numbers converge to a specific value, but as i increase nseg i get different value!

Why it happens?

[thats_karlo]

Any suggestion?

[thats_karlo]

I can not figure out, what is the answer?!

[thats_karlo]

Please !!!!

Help me!

[thats_karlo]

Any comments?

[ted]

A comment about this equation
Itotal=(I_ionic+I_leak)*totalarea/100
In a model that has more than one compartment, the proper calculation of total
membrane current is

Code: Select all

   SUMMA area_of_compartment_j * membrane_current_density_in_compartment_j
    all
compartments

For example, in a model that has the pas mechanism and no other ionic currents, the
way to calculate total ionic current through the membrane of the cell is

Code: Select all

itotal = 0
forall for (x,0) itotal += area(x) * i_pas(x)
itotal /= 100