This paper is a very clear review of the main properties of the direct problem mostly for MEG and EEG. It is written by very famous specialists of teh domain and give a broad panel on the different subjects concerning this topic : head model, volume conduction, mathematical formulation and algorithmic implantation.
I have only one remark concerning the anisotropic model of figure 8. How the author define the conductivity tensor in the skull, since no information is given in the DTI images ?
ReviewerA: The review article is well written, and nicely details the physics behind volume conduction. The authors provide a very up to date review of the current state of art of patient specific head model generation. The article has an excellent reference list that is very current. I have no substanial comments, as the review is very well done and accurate. If possible it would be nice to see more about validation of the anisotropic conductor models with EEG measurements and source reconstructions.
Thank you for your comments with regard to our Scholarpedia article.
Answer to reviewer 1: We added some text to describe how we have modeled skull anisotropy. We also added text and references how we have modeled white matter anisotropy.
Answer to reveiwer 2: Our validation results are already for an anisotropic (skull) three-layer sphere model. We are currently working on further increasing our FE computational accuracy in multi-layer sphere models for EEG and MEG, especially with regard to local anisotropy. As soon as we have more validation results available, we will always update our volume conduction webpage.