[FieldTrip] channel type (EEG, EMG, etc.) and when to filter data

[Rodolphe Nenert]

Let me add my 2 cents :

I'm back to use fieldtrip after a long period, and now everything seems to
> work (I used .edf file and I had problem with trigger).
>
>
> congratulations.
>

Rodolphe: Congratulations too

>
> 1. I'd like to label my channel to select among EEG type, EMG type etc.
> because my acquire system labeled them all as EEG. When is it specified in
> cfg ? I can't find it! And if I can't, how can I exclude EMG,TRIGGER and
> EOG channels from ICA computation?
>
>
> you must have had a consitent way of plugging in the channels into your
> amplifier, haven't you? if yes, then you should find out which channel
> corresponds to which row in your EEG data and you can relabel them within
> Matlab.
>
> Your EMG, TRIGGER and EOG channels should also be easy to detect when
> looking at your data. but you should get back to your recording
> configurations (also data acquisition software) if you are interested in
> the positions / labels of the other EEG electrodes. You may want to keep
> your EOG channels if they have a common reference like the EEG channels.
>

Rodolphe: Same answer

>
> 2. I have a lot of channel, but ICA gave me back just 33 of them. How can
> I proceed to obtain a correct ICA from my 56 channels?
>
>
> you mean components?
>

Rodolphe: Did you use a PCA to reduce your components first?

>
> 3. is it wrong if I filter my data before ICA?
>
>
> no.
>

Rodolphe: I would tend to say yes. ICA needs a maximum of information to
separate the components,
See for example Snyder and Foxe (2010) where they used ICA to get
components with a dominant of alpha oscillations. They argued that
filtering before is making ICA analysis worse

>
> 4. If I use ICA probably I can't use other source separation method (like
> BSS) to analyze my data, am I wrong?
>
>
> dunno.
>
Rodolphe : as ICA is a BSS, what other method did you have in mind?

>
> good luck,
> n
>
>
> Rodolphe Nenert, PhD.
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