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Bug 2279 - default conductivity values at different inputs of concentricspheres are inconsistent?

Reported 2013-09-09 17:35:00 +0200
Modified 2013-09-10 16:18:37 +0200
Product: FieldTrip
Component: documentation
Version: unspecified
Hardware: PC
Operating System: Windows
Importance: P3 normal
Assigned to: Lilla Magyari
Depends on:
See also:

Lilla Magyari - 2013-09-09 17:35:52 +0200

Hi, I run the concentricspheres method of prepare_headmodel with 3 different type of inputs, and I am wondering whether conductivity with value 1 is realistic. 1 compartment mesh output conductivity value: 1 3 compartments mesh output conductivity values: [0.3300 0.0042 0.3300] 4 compartments mesh output conductivity values: [0.3300 1 0.0042 0.3300] Should we change the default values to more realistic ones also at 1 or 4 compartments? And actually, the default conductivities are not documented at all. Lilla

Lilla Magyari - 2013-09-09 17:52:06 +0200

(In reply to comment #0) of course, the 1 layered one does not make too much sense. Or does it?

Robert Oostenveld - 2013-09-10 11:10:21 +0200

(In reply to comment #1) the one-layered one is indeed not meant to represent any true physiological model. It is there just for testing purposes.

Lilla Magyari - 2013-09-10 15:00:03 +0200

I guess the conductivity 1 in the 4 layer mdoel is supposed to be the conductivity of the CSF. When I asked Johannes what kind conductivity they use for CSF in FEM, he wrote: 1.79. Should I change it? Should I put the default conductivity values into the documentation of ft_headmodel_concentricspheres? (In reply to comment #2)

Lilla Magyari - 2013-09-10 16:09:25 +0200

(In reply to comment #3) I guess it is not good to change it because of backwards-compatibilty issues.

Robert Oostenveld - 2013-09-10 16:18:37 +0200

(In reply to comment #3) please don't make any changes yet. See which was contributed to Scholarpedia by Carsten and Jan de Munck. Jan has been working on EIT, which is reflected in some self-citations. the 1.79 is the value from however reports other values the [0.3300 1 0.0042 0.3300] sequence is normalized to CSF conductivity. I don't recall what the reference for these values is, but it was in use in BESA a long time ago (and perhaps still). I consider it a sensitive decision. Perhaps you could start with a FAQ: What is the electrical conductivity of the human head?