[Eeglablist] Interpolate 8 channel montage

[Kavanaugh, Brian]

Very useful, thanks Makoto!

On Mon, Aug 17, 2020 at 4:14 AM Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
wrote:

> Dear Brian and Zaeem,
>
> I discussed the validity of the average reference on your '20-40' system. I
> wrote 'Some people say no, but I think it is fine' but I was told it is NO.
> So let me give you that feedback here.
> The reason is described below--this is taken from Electric Field of the
> Brain by Nuenz and Srinivasan in p.298. The equation (7.12) referred to
> there should be (7.10) which is in p.295. If you want to see the copy of
> the page p.295, please let me know.
>
> Makoto
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> ...While the average reference offers theoretical as well as practical
> advantages, it is effective only if there are a sufficient number of
> electrodes (perhaps 64 to 128 or more) distributed over the entire scalp,
> including (if practical) samples on the lower surface of the head.
> Practical considerations that limit information from the lower surface of
> the head include muscle sources and other artifacts. The average reference
> is probably a poor choice for use with the standard 10/20 system (Fein et
> al. 1988). That is, the first term on the right-hand side of (7.12) is
> expected to yield very inaccurate estimates of the surface integral of
> potential when sparse electrode arrays are used.
>
> On Thu, Jul 30, 2020 at 12:14 PM Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
> wrote:
>
> > Dear Brian and Zaeem,
> >
> > My first data I analyzed had only seven electrodes.
> > Because these electrodes were placed symmetrically to both left-right and
> > anterior-posterior axes, it was like an extremely sparse full-scalp
> > recording (something like 20-40 system, instead of 10-20)
> >
> > You can process such data normally except for the following points:
> >
> >    - Electrode interpolation--could be very rough
> >    - Average referencing--Some people say no, but I think it is fine to
> >    go ahead if the electrode coverage is more or less uniform across the
> scalp.
> >    - Dipole fitting--the result accuracy (?) is naturally limited, though
> >    you tend to see smaller r.v. (why? Because less data needs to be
> >    approximated)
> >
> > In any case, as long as you describe these limitations clearly in your
> > report, it is fine.
> >
> > Makoto
> >
> >
> > On Thu, Jul 23, 2020 at 8:14 AM Kavanaugh, Brian <
> > brian_kavanaugh at brown.edu> wrote:
> >
> >> Zaeem,
> >>
> >> This is quite useful, thank you very much!
> >>
> >> Brian
> >>
> >> On Mon, Jul 20, 2020 at 12:17 PM Zaeem Hadi <zaeemhadi at ymail.com>
> wrote:
> >>
> >> > Hi Brian,
> >> >
> >> > I have been working with 8 channel dataset. However, I have avoided
> >> using
> >> > the clean_rawdata plugin. The reason being the eye blinks, which are
> >> quite
> >> > high in amplitude and also present in other channels to some degree.
> And
> >> > thus clean_rawdata would almost always reject 2 or 3 channels. And
> >> > interpolating so much data on just 8 channels wouldn't make sense. But
> >> if
> >> > you have relatively clean data, you might be able to use it.
> >> >
> >> > To avoid that, I am using the pop_eegthresh(ALLEEG) function to
> >> > semi-automatically reject epochs based on amplitude thresholding. For
> >> some
> >> > reason, it is not available through GUI.
> >> >
> >> > That being said, I have interpolated some channels in my data due to
> >> > excessive noise at the Alpha frequency range, but then I reduced the
> >> number
> >> > of Independent components being determined using 'pca' option in
> infomax
> >> > ICA, as suggested by Makoto in his pre-processing pipeline.
> >> >
> >> > Kind Regards,
> >> >
> >> > Zaeem Hadi
> >> >
> >> > Brain and Vestibular Group
> >> > Imperial College London
> >> > On Monday, July 20, 2020, 10:40:00 AM GMT+1, Kavanaugh, Brian <
> >> > brian_kavanaugh at brown.edu> wrote:
> >> >
> >> >
> >> > Hi everyone,
> >> >
> >> > We are hoping to analyze a previously collected dataset that used an 8
> >> > channel montage. Does anyone have any experience analyzing such a
> small
> >> > amount of electrodes? We are specifically curious about channel
> >> > interpolation options if channels are removed via clean_rawdata. Can
> we
> >> > follow a similar approach that we use for 32/64 channel data? Thanks
> >> > everyone!
> >> >
> >> > Brian
> >> >
> >> > --
> >> > Brian Kavanaugh, PsyD.
> >> > Pediatric Neuropsychologist, E. P. Bradley Hospital/Rhode Island
> >> Hospital
> >> > Assistant Professor (Research), Warren Alpert Medical School of Brown
> >> > University
> >> > _______________________________________________
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> >> >
> >>
> >>
> >> --
> >> Brian Kavanaugh, PsyD.
> >> Pediatric Neuropsychologist, E. P. Bradley Hospital/Rhode Island
> Hospital
> >> Assistant Professor (Research), Warren Alpert Medical School of Brown
> >> University
> >> _______________________________________________
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> >>
> >
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-- 
Brian Kavanaugh, PsyD.
Pediatric Neuropsychologist, E. P. Bradley Hospital/Rhode Island Hospital
Assistant Professor (Research), Warren Alpert Medical School of Brown
University