Hi all,
I have quite a few questions about choosing the Maxfiltering parameters, with the aim of working with data in the independent component domain. I'm working with combined M/EEG data (with cHPI) that is full of eye-movements.
For the ICA I have to do movement correction to fix the source-sensor configuration and to transform the different trials to same head position. I'm transforming the location to default head position, with changing the default location on some subjects where Maxfilter reports too large corrections otherwise (the 25mm limit). About the 'adjust initial hpifit consistency' option: It seems to be off by default, but isn't it better to always assume the HPI coils could have moved? Doing this will not introduce unnecessary variation to the source-sensor stationarity?
Then about tSSS: I've read that tSSSing will result in different parts of the data having different rank, which could be a problem for ICA. Would I be better off with doing only SSS? As a note, I'm not looking to remove the eye movement generated signals at this point as the ICA method I've chosen works great with those. But given that I have the EEG also, will I have to use tSSS?
Also the "Warning: Spatiotemporal signal space separation (tSSS) may diminish brain signals arising from very strong, superficial sources" is worrying. What would be considered very strong source? Would this include the eye movement related signals?
Sorry if these are very basic questions, my background is in EEG and all these possible adjustments of Maxfiltering settings seem important considering ICA, but I can't seem to find any relevant discussions. I'm also asking these as I've now done ICA (with combined M/EEG, tSSS'd data, that's moved to default head position with adjusted hpifits) and the results were pretty much on par with doing everything with the EEG sensors only, which seems a let down. I'm also seeing a lot of eye movement components that have weird topographies when looking at the gradiometers, while with EEG only I'm getting much fewer and clearer eye movement ICs.
Best regards,
Tatu
P.S.
Maxfilter version is 2.2.15
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