[FieldTrip] Problems with Neuromag Data after SSS

Stephan Moratti smoratti at psi.ucm.es
Fri Jun 17 09:01:45 CEST 2011


Hello everybody,

I had no problems reading Neuromag data, but when I want to read data  
treated with SSS I get the following error:

??? Error using ==> fiff_read_tag at 232
Cannot handle other than dense or sparse matrices yet

Error in ==> fiff_open at 80
     tag = fiff_read_tag(fid,dirpos);

Error in ==> fiff_read_meas_info at 82
     [ fid, tree ] = fiff_open(source);

Error in ==> ft_read_header at 1049
     orig = fiff_read_meas_info(filename);

Error in ==> mytrialfun_Neuromag_face at 3
hdr = ft_read_header(cfg.dataset);

Error in ==> ft_definetrial at 139
     trl   = feval(cfg.trialfun, cfg);

Any idea, what I could do?

Best,

Stephan


El 17/06/2011, a las 0:37, Rodolphe Nenert escribió:

> Im still afraid that the power of this analysis will be very low.
> Maybe you can try an ICA on your fMRI data and try to correlate each  
> component with your EOG timecourse.
>
> Rodolphe N.
>
> On Thu, Jun 16, 2011 at 1:16 PM, frank at greenant.net <fieldtrip at greenant.net 
> > wrote:
> It's a bit of a unique experiment, we're trying to use an ECG machine
> to acquire EOG, so it's only a single output channel.
>
> i guess what I need is a temporal ICA rather than a spatial one...
>
> On 17/06/2011, at 2:48 AM, Rodolphe Nenert wrote:
>
>> To summarize, the ICA will decompose your signal into as many  
>> components as Electrodes.
>> Therefore, trying to decompose only one source is useless.
>> Did you use a full net of electrodes into your MRI machine or only  
>> EOG electrodes?
>>
>> Hope this helps,
>>
>> Rodolphe N.
>>
>> On Thu, Jun 16, 2011 at 11:42 AM, frank at greenant.net <fieldtrip at greenant.net 
>> > wrote:
>> I am trying to use fieldtrip to filter EOG data obtained in an MRI.
>> I want to be able to spot the saccades in the samples and ideally  
>> measure their onset at the
>> end of each trial.
>>
>> As you may guess, it's quite noisy and it's broad spectrum noise,  
>> despite pre-filtering.
>>
>> Ideally, I would like to isolate the component that corresponds to  
>> the MRI interference
>> and then filter this out.
>>
>> I have managed to import the data and can run ft_componentanalysis
>> but it fails with:
>>
>> runica() - data size (1,30720) too small
>>
>> My data is single channel, 40 epochs, each of 6 seconds (time  
>> locked to stim onset but not saccade onset)
>> Is there a different method I should be using?
>>
>> I have posted some sample data and the current script (which reads  
>> in the
>> data and runs preprocessing) to the following urls:
>>
>> http://greenant.net/temp/1_2_MRI_2011-04-29%2016:19:33.mat
>> http://greenant.net/temp/EOG_analysis.m
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>
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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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