[FieldTrip] MEG grad data after ICA cleaning

Frédéric Roux f.roux at bcbl.eu
Thu Mar 6 11:01:02 CET 2014

Dear Haiteng,

thx for your response.

The reason why the grad field did not appear in my data-structure was that
there was no grad field prior to the call to ft_rejectomponent.

After modifying my code to:

data.grad = data.hdr.grad;

cfg = [];
cfg.component = comp_idx;
new_data = ft_rejectcomponent(cfg,comp,data);

I found that new_data has a grad field which has been adjusted for the rejected

A question related to this issue is whether it matters if I used two different
fieldtrip versions for doing the ICA decomposition (fieldtrip-20131120) vs. 
component rejection (fieldtrip-20140304)?
Does anyone know if there are any changes between these versions that could 
have an effect on my data?

Best regards,


Frédéric Roux

----- Original Message -----
From: "Haiteng Jiang" <haiteng.jiang at gmail.com>
To: fieldtrip at science.ru.nl
Sent: Thursday, March 6, 2014 9:37:18 AM
Subject: Re: [FieldTrip] MEG grad data after ICA cleaning

Hi Fred, 

I use the same code , but the updated grad is stored in the data. meg_data.hdr.grad is the grad before ICA. After ICA , grad needs to be adjusted ,which is used for the later source reconstruction . Do you have the latest FT ? 



Message: 5 
Date: Wed, 5 Mar 2014 16:28:58 +0100 (CET) 
From: Fr?d?ric Roux < f.roux at bcbl.eu > 
To: FieldTrip discussion list < fieldtrip at science.ru.nl > 
Subject: [FieldTrip] MEG grad data after ICA cleaning 
Message-ID: < 341671566.860154.1394033338749.JavaMail.root at bcbl.eu > 
Content-Type: text/plain; charset=utf-8 

Dear all, 

I am using ICA to clean my MEG-data before source analysis. 

My code looks as follows: 

cfg = []; 
cfg.component = [comp_idx]; 

meg_data = ft_rejectcomponent(cfg,comp,meg_data); 

However, after the call to ft_rejectcomponent there is no grad field in 
the meg_data structure. Rather, the grad field ist located under 

Is this the grad-field that I am supposed to use further downstream in the 
analysis pipeline, or should there be a grad-field under meg_data.grad? 

Any help would be much appreciated. 



Haiteng Jiang 
PhD candidate 
Neuronal Oscillations Group 
Donders Institute for Brain, Cognition and Behaviour 
Centre for Cognitive Neuroimaging 
Radboud University Nijmegen 

Visiting address 

Room 2.32 
Donders Centre for Cognitive Neuroimaging 
Kapittelweg 29 
6525 EN Nijmegen 
the Netherlands 

Tel.: +31 (0)243668291 
Web: https://sites.google.com/site/haitengjiang/ 
fieldtrip mailing list
fieldtrip at donders.ru.nl

More information about the fieldtrip mailing list