[Mne_analysis] Maxfilter and PCA-mag-v# projections

[Denis A. Engemann]

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I’d say if your data is clean enough to do without maxfilter then don’t bother with it. The proj approach is less invasive and more conservative.

> On 16 Jul 2019, at 18:26, Marijn van Vliet <w.m.vanvliet at gmail.com> wrote:
> 
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> Hi Denis,
> 
> thanks for confirming that the PCA projections are indeed dropped.
> Q1: I’m careful to take bad channels into account. However, I don’t have access to a crosstalk file or a fine calibration file. Maybe these will make all the difference.
> W2: I guess you are right in that I don’t *need* maxfilter, since the data is pretty clean to begin with. I was just wondering about the interplay between the PCA projections and maxfilter, since the projections seem superior in this case.
> 
> best,
> Marijn.
> 
>> On 16 Jul 2019, at 18:52, Denis-Alexander Engemann <denis.engemann at gmail.com> wrote:
>> 
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>> 
>> First they are discarded as you project to the low rank coordinate system of maxfilter. After this the SSPs are not valid any longer. Question : do you take into account bad channels before computing maxfilter? It sounds as if something is not right with its computation.
>> Question 2: if your data looks good, do you need maxfilter then in the first place?
>> 
>> Denis
>> 
>> On Tue 16 Jul 2019 at 15:32, Marijn van Vliet <marijn.vanvliet at aalto.fi> wrote:
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>> Dear MNE users,
>> 
>> can anyone enlighten me a little about the three 'default' projections 
>> PCA-mag-v1, PCA-mag-v2 and PCA-mag-v3. Where do they come from and why are they 
>> "discaded" by the maxfiltering process? My mags look pretty clean with them 
>> applied, but after maxfiltering, they look much worse, similar to not applying 
>> the PCA projections.
>> 
>> best,
>> Marijn.
>> 
>> 
>> -- 
>> Marijn van Vliet
>> Postdoctoral Researcher
>> Department of Neuroscience and Biomedical Engineering
>> Aalto University, Finland
>> 
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