[FieldTrip] Problems with Neuromag Data after SSS

[Laurence Hunt]

Hi Stephan,

Did you do anything else to the data besides applying SSS? I use SSS on all my data and haven't encountered this problem before. Does it apply to all your datasets or just one specific file?

Laurence

===========================================
Laurence Hunt, DPhil Student
 Centre for Functional MRI of the Brain (FMRIB), 
University of Oxford
lhunt at fmrib.ox.ac.uk
Phone: (+44)1865-(2)22738
===========================================

On 17 Jun 2011, at 08:01, Stephan Moratti wrote:

> 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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