I would like to perform a multitaper time-frequency decomposition as allowed by very recents updates in brainstorm. This involve the ft_mtmconvol function from fieldtrip but I encounteer some difficulties in setting the analysis parameters directly through the bstm interface.

The ft_mtmconvol fieldtrip function need 4 inputs - i.e. the frequencies of interest, the time-interval of interest, the length of the sliding time-window in seconds and the width of frequency smoothing in Hz. In the brainstorm interface however, what is the “modulator factor” (the number of cycles?), “the time resolution” and the “time step” parameters?

Many thanks in advance for your answer!
Best,
Emilie

Hi Francois,
again, I have basic question. What does “timwin = repmat(time_resolution, 1, length(frequencies))” mean?
I know that “when choosing this parameter it is important that a full number of cycles fit within the time-window for a given frequency.” but I can’t understand it. I want to set parameter of sliding time window as “5 cycles per time-window”.
Could you more information about it?

This means that the same timwin is used for all the frequencies. All the solutions I could think of for allowing different time windows for the different frequencies seemed too complicated. In Brainstorm, there is the additional constraint that things need to fit in an interface, and that we are trying to keep the list of options as condensed as possible.

But we can probably improve this initial draft, maybe by replacing the Brainstorm parameter “time_resolution” by a parameter “number of cycles”, and computing the FieldTrip parameter timwin for each frequency separately. I’m not sure how to set timeoi accordingly though, I’m not really good with all these concepts.