beamforming: length of data pieces

[Daniel Jokisch]

Hi,

I am localizing oscillatory sources using beamforming. When comparing
the activation in the prestimulus to the activation in the poststimulus
interval I was wondering if the data pieces must have the same length.
A prerequisite is that the length of a data piece must have the length
of a fix number of oscillatory cycles. Is it theoretically possible to
compare activation in a prestimulus interval to activation in a
poststimulus interval which is twice as long as the prestimulus interval?

A second question concerns the averaging over the same subjects in
different recording sessions (meaning that there are two sets of
headlocalization parameters and two headmodels for the same subject). Is
it necessary to normalize the data before using the function
sourcegrandaverage or can I use directly the output of the function
sourceanalysis as input for sourcegrandaverage?

Best,
Daniel

--
Daniel Jokisch, PhD
F.C. Donders Centre for Cognitive Neuroimaging
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Phone:  +31 24 36 68294
Fax  :  +31 24 36 10989

http://www.ru.nl/fcdonders/