[Eeglablist] high density EEG, source localization and electrode positions

[Scott Makeig]

Sara -

Measuring the positions of a subset of the electrodes is an interesting idea
(for speed). We are exploring electrode position measurement now in the lab,
and will consider trying this ourselves. You should be aware that Polhemus'
magnetic systems are inaccurate if any magnetic metal is nearby. There are
also ultrasound and camera-based systems available (at various prices). I
believe it should be possible to develop low-cost simple camera-based
software, but the development process would in itself cost time and money.
I'd be interested in hearing others' experience with electrode position
measurement.

Scott Makeig

PS Zeynep Akalin Acar's NFT can build an individualized BEM head model from
electrode positions, with or without MR (though with MR is better, of
course). She is currently preparing a simulation paper on the consequences
of not using MR for source localization -- or using inaccurate electrode
positions on a standard head model, as is most common in EEG labs today.

PPS Nima Bigdely-Shamlo has contributed an EEGLAB function that can find
maximally uniformly-spaced subsets of an electrode montage.


On Thu, Jul 29, 2010 at 3:27 AM, Sara Graziadio <
sara.graziadio at newcastle.ac.uk> wrote:

> Hello everybody,
> We are setting up an ERP study with high density EEG (128 electrodes). We
> would like to localize sources from the ERP components and possibly to
> relate these data with fMRI activations. We would have MRI data of the
> subjects. We are now in the process of considering the possibility to use
> the Polhemus to digitalize the electrode positions and we found out that
> there are no papers (at least that I can find) that compare the accuracy of
> source localization with high density EEG adding the information about the
> positions of all the 128 electrodes, or of just a part of them (for example
> 30 evenly spread on the scalp and including some of the more external
> positions), or just using the standard 10-10 system locations. Does anybody
> of you have any thoughts about it? Have you had ever tried to compare the 3
> options I have described?
> Thank you very much
>
> Best wishes
>
> Sara Graziadio, PhD
> Research Associate
> Newcastle University
>
>
>
>
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-- 
Scott Makeig, Research Scientist and Director, Swartz Center for
Computational Neuroscience, Institute for Neural Computation, University of
California San Diego, La Jolla CA 92093-0961, http://sccn.ucsd.edu/~scott
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