[FieldTrip] problems with ft_sourcegrandaverage

[Chiara Spaccasassi]

Dear Fieldtrip community,

I am using Fieldtrip to run a source localization of TMS evoked potentials (TEPs) on EEG data. I decided to use the MNE method following the online tutorial (https://www.fieldtriptoolbox.org/tutorial/minimumnormestimate/). I was able to reproduce the analysis using my data and create the source localization figure. However, I noticed that the plot is representing the power of the data (avg.pow), which is not exactly what I was aiming for. Is there a way to create and plot the amplitude rather than the power of the signal - which I suppose is stored in the ‘moment‘ (.mom) field?

>From what I saw, it does not seem possible to compute such operation using the Fieldtrip functions showed in the tutorial. The problem seems to be that the structure of .mom is not equal to the pow’s one. Specifically, avg.pow is a 20484x3000 matrix of N source points x N time points. The .mom field contains instead a 20484x1 cell array and each cell is a 3x3000 matrix with the three rows supposed to be the three coordinates x,y and z of the source vector and the columns representing the time points. I was able to obtain a data structure similar to pow (20484x3) by using custom-made scripts to compute the average of the three axes (x, y, z) for each time point (3000) and source (20484). Is this method correct? Is there a better way to extrapolate the amplitude for each time x source point and to plot it?

Thanks in advance!


*******************************************************
Chiara Spaccasassi
Post-doctoral Researcher
Centre for studies and research in Cognitive Neuroscience (CsrNC)
Department of Psychology, University of Bologna
Via Rasi e Spinelli, 176, 47521, Cesena, Italy

Inviato da Posta<https://go.microsoft.com/fwlink/?LinkId=550986> per Windows 10

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