[FieldTrip] Value per parcel after running ft_virtualchannel

[Marta Stojanović]

Hi,

I hope this email finds you well. I have a question about obtaining one power value per parcel after using ft_virtualchannel. I guess there must be a way to create a dummy struct that could solve this problem, so apologies if there is a straightforward answer, but I am finding it hard to obtain one value per parcel after interpolating source data onto an atlas and running ft_virtualchannel.

I run ft_virtualchannel instead of ft_sourceparcellate because I want to keep trial information which I couldn’t keep with the output of ft_sourceparcellate. The output of ft_virtualchannel that I obtain through this looks like:

  struct with fields:

            trial: [142×246×1018 double]
            time: [1×1018 double]
            dimord: 'rpt_chan_time'
            label: {246×1 cell}
            cfg: [1×1 struct]
            grad: [1×1 struct]
            sampleinfo: [142×2 double]
            trialinfo: [142×2 double]
            brainordinate: [1×1 struct]




After I use some fields from a previously generated average of alpha power along with fields from the ft_virtualchannel output to create the following dummy source struct:

     trial: [142×246 double]
     time: 0
     cfg: [1×1 struct]
     dim: [26 33 28]
     pos: [24024×3 double]
     pow: [24024×1 double]

The data is collapsed across time, but the pow field is the multiplication of the dimensions of the tissue (26 * 33 * 28), rather than a value per parcel.

I know from the Fieldtrip tutorials online that the output of ft_sourceparcellate can look like this:

parcel =
           label: {1x116 cell}   % brain parcels labels
           anatomy: [116x1 double]
           anatomydimord: 'chan_unknown'
           pow: [116x1 double] % one value of brain activity per parcel
           powdimord: 'chan'
           brainordinate: [1x1 struct]
           cfg: [1x1 struct]


I’m wondering if you could perhaps point me to the most effective way to replicate this output/reshape the output of ft_virtualchannel or somehow with ft_virtualchannel in the easiest possible way obtain one value per parcel. Essentially, I’m most interested in replicating or obtaining the ‘pow’ field from the ft_sourceparcellate output where I would have one power or activity estimate per parcel.


I hope the question makes sense, and I can of course elaborate or explain further if not. Either way, thanks a lot in advance!


All the best,
Marta

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