Dear Vladimir,
Thanks very much for your fast and helpful reply! However, I am uncertain
concerning one of your answers.
> Interestingly, windowing my data around 40 Hz (which corresponds to
> the auditory stimulation frequency) reveals auditory activation.
> However, if I apply a more broadbent window of 3:45 Hz all auditory
> activation seems to be gone. In this case, all activation seems to be
> localized in visual cortex (Importantly, visual stimulation occurred
> at a frequency of 6 Hz.) Is it possible that stronger visual activation
outperforms auditory activation?
>
Yes, it's possible and the results you get empirically answer your question.
The inversion aims at producing a solution which explains maximal variance
in the data. Therefore if the signal at low frequencies is much stronger
than at high frequencies the algorithm will focus at modelling the low
frequencies. Windowing after inversion will not solve this because at this
stage the solution is already computed. So if this is indeed a problem for
you, you should filter your data to the range of interest before the
inversion.
If I understand you correctly
If I understand your answer correctly, windowing has no effect on the
solution of the source localization. However, depending on the frequencies I
chose for windowing, auditory activation becomes "visible" (that is in the
case of narrowband windows) or "invisible" (in the case of broadbent
windows). Since the solution has been determined during inversion, why can
the auditory activation only been "seen" during narrowband windowing?
Thanks again and best,
Anette
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