Forward model conductivities

Dr. Carsten Wolters carsten.wolters at UNI-MUENSTER.DE
Tue Oct 26 09:11:47 CEST 2010

Dear Stanley and Paul,

I agree to what Stanley wrote about the skull inhomogeneities, it fits
to what we described in a recent publication:
    author = {Dannhauer, M. and Lanfer, B. and Wolters, C.H. and
Kn{\"o}sche, T.},
    title = {Modeling of the Human Skull in {EEG} Source Analysis},
  journal =      "Human Brain Mapping",
  note    =      "DOI: 10.1002/hbm.21114, PMID: 20690140",
  year =         "2010",
Best regards

Stanley Klein wrote:
> Dear Paul and Carsten,
> The conductivity ratio of 1/20 that you mention is indeed on the low
> side of
> many present estimates. It is way lower than the Rush  &  Driscoll  1/80
> ratio that we used in our 30 year old "Ary Correction" paper that
> examined
> the effect of skull and scalp thickness. My big worry however is
> not simply to find the ratio (taking individual differences into
> account). but
> also to get estimates of the differences in conductivity across the skull.
> I'm pretty confident that such inhomogeneities are present and that
> they will
> have significant effects on the BEM forward models. The inhomogeneities
> will not only affect the effective depth of sources but also can
> laterally shift
> their locations to places on cortex with very different surface normals.
> An important aspect of our EEG/MEG source localization work is to learn
> how to calibrate each individual's conductivity partly based on
> differences
> in EEG vs MEG localizations.
> best,
> Stan
> On Mon, Oct 25, 2010 at 4:40 AM, Paul Czienskowski <paul_c at
> <mailto:paul_c at>> wrote:
>     Dear all,
>     Alexandre Gramford pointed out to me that there was some
>     discussion ongoing on which conductivities to use for
>     EEG-Forward-Modeling and I'd like to move this discussion more to
>     public for it could be interesting for many of us.
>     I was recently overflying some papers concerned with that very
>     issues and I made some interesting and discoveries, especially in
>         Conductivity of living intracranial tissues. by Latikka J,
>         Kuurne T, Eskola H.
>         The electrical conductivity of human cerebrospinal fluid at
>         body temperature by Baumann et al.
>     The first one measured the conductivities (or resistivities) of
>     living brain tissue and came to values of 3.51 Ohms*m and 3.91
>     Ohms*m for grey respectively white matter and 0.80 Ohms*m for the
>     CSF (which are about 0.28, 0.256 and 1.25 S/m). In contrary the
>     second one found a value for 1.79 S/m for CSF at body temperature
>     where it was about 1.4 S/m at room temperature. The Skull-To-Brain
>     conductivity ratio was measured for example in
>         Estimation of /in vivo/ brain-to-skull conductivity ratio in
>         humans by Yingchun Zhang, Wim van Drongelen, and Bin He
>     where they found a ratio of about 1/18.7 which is way larger than
>     the commonly assumed value.
>     I would appreciate very much if many of you could contribute to
>     this discussion by telling us which values you use for the
>     conductivities and on which publications the are based.
>     Best,
>     Paul
>     --
>     Paul Czienskowski
>     Max Planck institute for human development
>     Lentzeallee 94
>     14195 Berlin
>     Björnsonstr. 25
>     12163 Berlin
>     Tel.: (+49)(0)30/221609359
>     Handy: (+49)(0)1788378772
> ------------------------------------------------------------------------

PD.Dr.rer.nat. Carsten Wolters
Institute for Biomagnetism and Biosignalanalysis
University of Muenster, 48149 Muenster, Germany
Tel.: +49/(0)251-83-56904
Fax:  +49/(0)251-83-56874

You are receiving this message because you are subscribed to
the  FieldTrip list. The aim of this list is to facilitate the discussion
between  users of the FieldTrip  toolbox, to share experiences
and to discuss  new ideas for MEG and EEG analysis.
See also

More information about the fieldtrip mailing list