[FieldTrip] bemcp vs dipoli

[Alexandre Gramfort]

hi Maris,

you can have a look at:

http://www.hindawi.com/journals/cin/2011/923703/

especially:

http://www.hindawi.com/journals/cin/2011/923703/fig12/

LC (linear collocation) is bemcp and LCISA is dipoli. When using ISA
(isolated skull approach)
accuracy is better.

In summary use dipoli if you can.

Hope this helps,
Best,

Alex


On Wed, Nov 4, 2015 at 12:00 AM, Maris Skujevskis
<icelandhouse at gmail.com> wrote:
> Hi Fieldtrip users,
>
> When constructing a volume conduction model for EEG using the boundary
> element method (BEM), there are two methods available: 'dipoli' and 'bemcp'.
> Besides technicalities (i.e., 'dipoli' only available on Linux), are there
> any differences that you know of/have experienced that make one method
> better (more reliable, more accurate, or anything else that makes you prefer
> one rather) than the other?
>
> For some of my EEG subjects, 'dipoli' succeeds where 'bemcp' fails. During
> processing with 'bemcp' there is a "warning: Matrix is singular, close to
> singular or badly scaled. Results may be inaccurate. RCOND = NaN", with the
> end result being that vol.mat contains NaNs.
> The input in both cases, besides the method chosen, is identical.
>
> Taking one step back in the processing pipeline, I am aware that a poor
> segmentation outcome might be a/the cause of the warnings and eventual
> errors when constructing a volume conduction model. But in general this
> should hold equally for both methods. What I am wondering about is why one
> method might deal more successfully than the other with the same input.
>
> Best,
> Maris
>
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