tuneCV and mMS model - tissue doesn't activate

Question

Hi,

I want to use the mMS model in my simulations. However, I don't know which values for conductivity I have to use, as for different combinations in tuneCV simulations the tissue is not activating. 

I tried with:

tuneCV --resolution 200 --model mMS --flavor petsc --velocity 0.3 --tol 0.001 --converge True

However the tissue is not activating with these settings. I tried different things here (varied values for --stimS, --resolution, --dt, --resolution), but somehow the tissue is still not activating. 

I really dont know which values for --gi and --ge I can give as 'first guess' and furthermore what values for conductivity I have to use for a specific conduction velocity in my tissue simulations. 

(when using for example --model TT2 it works perfectly)

Next to that, when making a mesh of a 1D cable with 1 element thick (resolution 200 um) and applying a stimulus at the left corner with strength 30 - the tissue does activate (for the mMS model). So it has to work with tuneCV right? .. But maybe I am missing something, I hope you can help. 

Thank you

Justina

Answer 1

tuneCV uses the LAT function to detect activation at the end of the strand. tuneCV uses a threshold of -20mV transmembrane voltage for activation:

https://git.opencarp.org/openCARP/carputils/-/blob/master/carputils/tuning.py#L435

The Mitchel Schaeffer model by default has a pseudo-voltage ranging from 0 to 1 ("mV"), thus never crossing this threshold of -20mV from below to above. What you could do is to change the V_min and V_max parameters of the ionic model to for example -80mV to +20mV:

https://git.opencarp.org/openCARP/openCARP/-/blob/master/physics/limpet/models/MitchellSchaeffer.model