[FieldTrip] Leadfield of one condition with two different 'grad' structures

Sara Aurtenetxe s.aurtenetxe at bcbl.eu
Thu Sep 17 10:09:11 CEST 2015

Dear Stephan, 

Thank you for your rapid answer. 

Indeed, I did measure the coils position. 
This approach seems the most suitable one so 
I will follow it and see how the results look like. 

Thank you!


Sara Aurtenetxe

----- Original Message -----
From: "smoratti" <smoratti at psi.ucm.es>
To: "FieldTrip discussion list" <fieldtrip at science.ru.nl>
Cc: "Sara Aurtenetxe" <s.aurtenetxe at bcbl.eu>
Sent: Wednesday, September 16, 2015 3:57:30 PM
Subject: Re: [FieldTrip] Leadfield of one condition with two different 'grad' structures

Dear Sara,

Did you measure for each run the HPC coil position in order to determine the relative sensor position with respect to the head? If so, you could calculate the lead field for each run separately, source localize for each run and then collapse the runs after source localization.



Stephan Moratti, PhD

see: Stephan's research profile

Universidad Complutense de Madrid
Facultad de Psicología
Departamento de Psicología Básica I
Campus de Somosaguas
Despacho (Office) 1326-0 
28223 Pozuelo de Alarcón (Madrid)


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)

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

El 16/09/2015, a las 15:21, Sara Aurtenetxe escribió:

> Dear all, 
> I would appreciate to get some advice on the following.
> I am computing the leadfield (ft_prepare_leadfield) for the subsequent source analysis (ft_sourceanalysis) of ERF data acquired with Elekta Neuromag system. 
> My experiment is acquired in a unique run, including 3 randomized conditions for each participant normally. 
> Therefore, the unique 'cfg.grad' structure is used for the leadfield computation of each participant.
> However, due to a must, the experiment was recorded into two independent runs (splited) for one of the participants. Here comes the issue: 
> Given that the 'grad' structure is specific to each run, this participant turns to with two different 'grad' structures for the same condition.
> My question is: which is the most suitable approach to compute the leadfield of one condition when the data comes from two different runs, so when having two different 'grad' structures?
> I would say that I should compute the leadfield and the sourceanalysis for each run and condition separately, and then join the solutions of the same condition. 
> But I wonder if this is a correct approach and/or if there is any additional/more appropriate approach for that. 
> Any comment will be very appreciated.
> Thank you in advance.
> Best,
> Sara
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