[FieldTrip] Incorporating White Matter conductivity anisotropy into FEM simbio

[Ravi Mill]

Dear Fieldtrippers


I have applied the FEM simbio head modeling pipeline implemented in Fieldtrip to my EEG data. My understanding is that this pipeline assumes isotropic conductivities for 5 head compartments (as specified by cfg.conductivity in ft_prepare_headmodel). After reading some papers (e.g. Vorwerk et al 2014 https://doi.org/10.1016/j.neuroimage.2014.06.040), it seems like incorporating white matter conductivity anisotropy has a relatively small albeit significant effect on the source solution. I am interested in comparing FEM results when treating white matter as anisotropic. My questions are as follows:


  1.  Is there a way to implement the FEM simbio head model whilst treating WM as anisotropic within Fieldtrip? If so, how would one do this (or are there any resources available that demonstrate this)?
  2.  From previous papers and some simbio documentation (https://www.mrt.uni-jena.de/simbio/index.php/SIMBIO/Releasenotes/Examples) it seems like diffusion MRI data is required to calculate the WM conductivity for each individual subject. I only have T1 and T2 scans for my subjects. So would it be possible to use WM anisotropic information obtained from some kind of diffusion MRI group average/atlas instead (accepting some loss in subject-level precision)? If so, does such a group average/atlas exist?


Any help would be greatly appreciated!


Thanks

Ravi



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