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

Nathan Weisz nathanweisz at mac.com
Fri Mar 16 09:53:20 CET 2012


> 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).


> 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.

> 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? 

> 3. is it wrong if I filter my data before ICA?


> 4. If I use ICA probably I can't use other source separation method (like BSS) to analyze my data, am I wrong?


good luck,

> Sorry if I post so much questions, but I'm back with fieldtrip and I want to improve my techniques.
> Ivano 
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