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
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