Dear SPM Masters,
Here's a more general and synthetic version of my previous question.
My doubt: what is the optimal baseline for EEG source reconstruction,
and specifically:
1) Is it problematic to set the baseline in a period that contains
(sensory) evoked responses? Is there a risk of suppressing the sources
of those evoked responses?
2) Otherwise, is it problematic to set a baseline much before the
relevant stimulus (in my case, 800 ms before)? How do slow drifts in
the data impact on source reconstruction?
Thanks,
Marco
On 3 December 2012 11:59, Marco Buiatti <[log in to unmask]> wrote:
> Dear SPM Masters,
>
> I have yet another doubt on EEG source reconstruction which might be
> of general interest. I have a priming design in which the target
> stimulus is preceded by a prime stimulus, presented either 800 ms
> before (if it's auditory) or 360 ms before (if it's visual). In my
> simplest case, I want to test the difference between two different
> conditions, both comprising both visual and auditory primes. My
> problem is to choose the most appropriate baseline for EEG source
> reconstruction.
>
> At the sensor level, since I am testing a difference that should not
> depend on the evoked response of the prime, it is common use to take
> the baseline in the 100-200 ms window before the target presentation.
>
> For source reconstruction, is the fact that the pre-target baseline
> contains the evoked responses of the prime problematic? Could it
> suppress the same kind of responses and/or generate "phantom
> responses"?
> Should I choose a pre-prime baseline (e.g. 800 ms before the target),
> at the risk of having more variability due to low frequency drifts?
> Data have been high-pass filtered at 0.3 Hz before epoching, in this
> case I might increase the high-pass filter cut-off of the continuous
> data.
>
> Thanks a lot 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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