[Eeglablist] Biosemi loc file

Thu May 3 09:40:11 PDT 2018

Hi Karolina,

So you could try this (someone please correct me if I am wrong).

You can get into the data of the EEG file through EEG.data. Then you can specify a channel like this EEG.data(1,:) and then you can replace it with the one that you want.

So, if B4 is number 36 then you can tell the EEG data in the 36th position to be replaced with EXG3, which should be 131st channel. Therefore you should be able to do it like so.

EEG.data(36,:) = EEG.data(131,:)

&

EEG.data(52,:) = EEG.data(132,:) % for B20 to EXG4

Kind regards,

Mark

________________________________
From: Karolina Broś <k.bros at uw.edu.pl>
Sent: 03 May 2018 17:12:02
To: Crook-Rumsey, Mark
Cc: eeglablist at sccn.ucsd.edu
Subject: Re: [Eeglablist] Biosemi loc file

Hi Mark,

thank you.

As for the externals, what I mean is that in the electrode set I was using two electrodes were permanently broken so I was using EXG3 and EXG4 (additional/external electrodes) in their place. For this reason I do not want to interpolate but just replace the signal from the B4 and B20 electrodes which were bad (and hence the signal is null or just noise) with the signal recorded on the EXG3 and 4. I know that this kind of replacement is possible in Fieldtrip for instance (I have a code for that), but I am not sure how this is done in EEGLAB.

I am thinking that I could just delete the bad electrodes and add those externals with the locations of the ones I am replacing, but this only fixes the locations I suppose....right? I would have to then just exclude bad electrodes.

I would be really grateful if anyone could help on this matter.

Thanks again!
Karolina

Pozdrawiam serdecznie
dr Karolina Broś

Institute of Applied Linguistics
University of Warsaw
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2018-05-03 18:02 GMT+02:00 Crook-Rumsey, Mark <mark.crookrumsey at ntu.ac.uk<mailto:mark.crookrumsey at ntu.ac.uk>>:

Hi there,

I also use a 128 biosemi. For some reason EEGlab is not letting me create a .loc file for you. However the file that I sent previously should work. If you type the code below into your command line in matlab it should look up the locations from the that .elp file. Do this after you have already imported your files into EEGlab.

% import channel info
EEG=pop_chanedit(EEG, 'lookup','G:\\Mark\\EEG Data\\Biosemi_128_sph.elp');  %change the last part in ' ' to where ever the file is saved

Alternatively, you could try the following in the command line:

pop_chanedit(readlocs('biosemi_eloc.txt', 'format', { 'labels' 'sph_theta_besa' 'sph_phi_besa' }, 'skiplines', 1)); % change the 'biosemi_eloc.txt' part to whatever your excel file is called with the locations.

I'm not sure what you mean by externals? If you find that you have bad electrodes you can remove them and leave them out, or you can interpolate them, which will create an artificial average from the surrounding electrodes.

 I hope none of that sounds condescending, I'm not sure what you have or have not already tried. Let me know if this helps.

Kind regards,

Mark

________________________________
From: Karolina Broś <k.bros at uw.edu.pl<mailto:k.bros at uw.edu.pl>>
Sent: 01 May 2018 19:11:04
To: Crook-Rumsey, Mark
Subject: Re: [Eeglablist] Biosemi loc file

Hi!

Thank you very much for the files but I have data recorded in a 128-electrode system. Maybe you have a loc file for that?

Also, I wanted to ask about replacing nad electrodes with the signal fro  externals. Should I just delete bad channels and add external electrodes with the locations of the replaced ones or is there some other procedure in EEGLAB for that?

On Tue, 1 May 2018, 19:58 Crook-Rumsey, Mark, <mark.crookrumsey at ntu.ac.uk<mailto:mark.crookrumsey at ntu.ac.uk>> wrote:

Hi Karolina,

Please let me know if this is of any use to you.

Kind regards,

Mark Crook-Rumsey

________________________________
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu<mailto:eeglablist-bounces at sccn.ucsd.edu>> on behalf of Karolina Broś <k.bros at uw.edu.pl<mailto:k.bros at uw.edu.pl>>
Sent: 27 April 2018 17:44:50
To: eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>
Subject: [Eeglablist] Biosemi loc file

Hello,

I wanted to ask about the Biosemi channel location files.
I was looking all over the internet but I have not found a loc or othe EEGLAB-accepted channel file for Biosemi 128'channel systems.

I do have the coordinates in an excel files but I don´t know how to convert them into a loc file or anything accepted by EEGLAB. Besides, I read that it is not straightforward and requires some computations because it´s different from the standard. I am new to EEGLAB and EEG in general and I am unable to make such computations on my own. I know that people use Biosemi data in EEGLAB so such files do exist.

Would it be possible for someone to share a loc file? I would be really grateful for your help.

Best regards,
Karolina Bros

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