[FieldTrip] [FieldTrip​] Data handling after excluding single sensors (Neuromag)

[Stephan Moratti]

Dear Jarang,

I think there are two options:

1.) You exclude as a pair, as combining the two orthogonal sensors you want to capture the different directions of the magnetic field.

2.) Or you look at the horizontal and vertical gradiometers separately. The following script should allow you to extract the two different sensor types

channel = ft_channelselection('MEG*2',data.label);
index = match_str(data.label,channel);
 
gradH_F = data;
gradH_F.powspctrm(:,1:102,:,:) = data.powspctrm(:,index,:,:);
gradH_S = data;
gradH_S.powspctrm(:,1:102,:,:) = data.powspctrm(:,index,:,:);
 
channel = ft_channelselection('MEG*3',data.label);
index = match_str(data.label,channel);
 
gradV_F = data;
gradV_F.powspctrm(:,1:102,:,:) = data.powspctrm(:,index,:,:);
gradV_S = data;
gradV_S.powspctrm(:,1:102,:,:) = data.powspctrm(:,index,:,:);

data is a grand mean time frequency matrix with keep individuals = yes. I hope that helps.

Best,

Stephan

El 10/04/2012, a las 11:40, Jarang Hahm escribió:

> Hi all,
>  
>  
> We are using Neuromag 306 sensors VectorView system.
> And only gradiometer sensors (204 sensors) are used for analysis.
>  
>  
>  
> In the artifact rejection, I excluded four bad sensors, not as a pair, among 204 sensors.
> 
> After time-frequency analysis, I got lost when combine the sensors.
>  
>  
>  
> How can I deal with the data with a single sensor in part?
>  
> Should I reject the sensor as a pair? Or, combine the signals only for the paired sensors?
>  
>  
> I want you to suggest the proper way to handle the data of one sensor in a pair.
>  
>  
>  
>  
> Thank you in advance,
> 
>  
>  
> Jarang Hahm
>  
>  
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________________________________________________________
Stephan Moratti, PhD

see also: http://web.me.com/smoratti/

Universidad Complutense de Madrid
Facultad de Psicología
Departamento de Psicología Básica I
Campus de Somosaguas
28223 Pozuelo de Alarcón (Madrid)
Spain

and

Center for Biomedical Technology
Laboratory for Cognitive and Computational Neuroscience
Parque Científico y Tecnológico de la Universidad Politecnica de Madrid
Campus Montegancedo
28223 Pozuelo de Alarcón (Madrid)
Spain


email: smoratti at psi.ucm.es
Tel.:    +34 679219982


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