Thanks Vladimir for the rapid response.
A related question:
I have 20 subjects, 64 channels, no single subject MRI and no
anatomical landmark (no digitization). I am looking for a quite subtle
effect which is significant at the sensor level (Fieldtrip non
parametric statistical analysis) but variable from subject to subject.
Due to this variability and the absence of single subject anatomical
landmarks, I thought that I could do source reconstruction only on the
grand-averaged ERP.
Does it make sense with this variability to do source reconstruction
on single subjects, or maybe do group inversion? Would this option
account better for covariance variability across subjects?
Thanks for your advice,
Best,
Marco
On 25 September 2012 21:02, Vladimir Litvak <[log in to unmask]> wrote:
> Dear Marco,
>
> It would be better to use normal or fine mesh if your computer power allows
> it. I think these days there is no reason to use coarse, just when SPM8
> first came out there were still many old an weak machines around. Hanning
> window indeed multiplies the response in time and suppresses the edges. If
> the interesting part of the response is in the middle of your time window it
> would be advisable to use it.
>
> Best,
>
> Vladimir
>
>
> On 25 Sep 2012, at 16:16, Marco Buiatti wrote:
>
>> Dear SPM masters,
>>
>> I am trying to perform source reconstruction on the grand-averaged
>> ERPs from an EEG study (BrainAmp, 64 channels) with 20 subjects. Since
>> the EEG electrode positions were not digitized, I am using the
>> standard EEG template with standard electrode positions.
>>
>> My problem is that I see a quite wide variability in the sources by
>> varying two parameters of the reconstruction:
>> 1) use of coarse or normal cortical mesh
>> 2) use or not of hanning window when inverting
>>
>> My questions are:
>> 1) Is it normal to see large variability when using normal or coarse
>> mesh? What would be the best for 64 electrodes?
>> 2) What does the hanning window exactly refers to? I intuitively think
>> that data in time are weighted by this window, but I could not find
>> the exact info on the manual.
>> 3) Any other important factor that you think is crucial for source
>> reconstruction in this case?
>>
>> Thanks for your feedback,
>>
>> Best,
>>
>> Marco
>>
>> --
>> Marco Buiatti, PhD
>>
>> CEA/DSV/I2BM / NeuroSpin
>> INSERM U992 - Cognitive Neuroimaging Unit
>> Bāt 145 - Point Courrier 156
>> Gif sur Yvette F-91191 FRANCE
>> Ph: +33(0)169.08.65.21
>> Fax: +33(0)169.08.79.73
>> E-mail: [log in to unmask]
>> http://www.unicog.org/pm/pmwiki.php/Main/MarcoBuiatti
>>
>> ***********************************************
>
>
--
Marco Buiatti, PhD
CEA/DSV/I2BM / NeuroSpin
INSERM U992 - Cognitive Neuroimaging Unit
Bāt 145 - Point Courrier 156
Gif sur Yvette F-91191 FRANCE
Ph: +33(0)169.08.65.21
Fax: +33(0)169.08.79.73
E-mail: [log in to unmask]
http://www.unicog.org/pm/pmwiki.php/Main/MarcoBuiatti
***********************************************
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