[FieldTrip] Running the ICA method to remove EOG/ECG artifact on Neuromag(*.fif) data

[Alexandre Gramfort]

Dear Panagiotis,

the only potential caveat I see for the inverse problem is that you
reduce the rank of your data but using ICA. To take care of this you
make sure that
your inverse solver takes it into account via the whitening noise
covariance matrix that should also be applied to the gain/leadfield
matrix.

Alex

On Fri, Apr 13, 2012 at 7:00 PM, Panagiotis Tsiatsis
<Panagiotis.Tsiatsis at tuebingen.mpg.de> wrote:
> On 4/13/2012 8:50 AM, Alexandre Gramfort wrote:
>>
>> but be careful when applying ICA on neuromag data as
>> channels have different types and you have signals
>> with 2 orders of magnitude difference between gradiometers
>> and magnetometers.
>>
>> I am curious to know if fieldtrip handles this properly? and if so how.
>
> Hi all,
>
> I am also working with CTF MEG data. What I ve been basically doing up to
> now was to split the datasets in two subsets: one containing only the
> MEGGRAD sensors (let s call it A)  and another containing all the rest (let
> it be B). Then I would apply ICA only on the set containing the main MEG
> sensors, subtract the EOG-related components and re-construct the data
> without them (A'). Finally, I would merge A' with B. This works fine and the
> results that I am getting are convincing, the only problem is that of course
> the reference channels are still contaminated. I don t know if this would be
> a problem in subsequent analysis, ie source localization, maybe somebody who
> has more experience further down this road could comment on that.
>
>
> Best,
> Panagiotis
>
> --
> Panagiotis S. Tsiatsis
> Max Planck Institute for Biological Cybernetics
> Cognitive NeuroImaging Group
> Tuebingen, Germany
>
>
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