source localization given induced spectra

John Iversen iversen at NSI.EDU
Mon Nov 3 18:26:11 CET 2008


Is there a way to do source localization on induced spectrograms?
(Induced spectra being the mean of individual trials' power spectra.)
Conceptually I am not sure how this would work, given that one starts
with topographies of real, positive-valued power, with no phase
information, so any dipole fit could be at best sign-
indeterminate.There is no facility within fieldtrip to do such a thing
as far as I can tell (induced spectra were calculated freqanalysis on
multi-trial data and are within the .powspctrm field of the result,
which is not handled by freq2timelock, and thus cannot feed any of the
localization routines).

What is of actual interest are task-related fluctuations of the power
around a (much larger, and topographically varied) baseline. Is there
a way to say where in the brain are the (presumed) subset of neural
sources that vary in power with time?



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