Dear Brainstorm users,
I have a question about the topography map. I have intracranial recordings (from both ECOG and SEEG) and I was trying to extract the values in uV displayed in a topography map at a given time sample.
For example, I have this topography for one patient, and for each channel, it is displayed a value of Voltage. If I want the vector containing these values, how can I get it? I tried to see in the function view_topography.m but I didn't understand what exactly is the F matrix (that in my understanding should be what I want).
From tutorial 5, I read this statement "A simple inverse problem + forward problem are solved to reconstruct the magnetic fields on a high-resolution surface". What is exactly the math underlying this operation for the topography map? What inverse and what forward problem are you using to draw this map? Is it the same as the classical:
sim_recordings=Gain*(ImagingKernel*sig_original)?
I guess that with this information I can get what I want. I hope I explained my issue clearly.
All my best,
Margherita
For example, I have this topography for one patient, and for each channel, it is displayed a value of Voltage. If I want the vector containing these values, how can I get it?
The values you observe in this figure are directly the values from the data file: you should rather try to obtain them:
- Either directly from the data files (F matrix, at the column corresponding to the Time point of interest): https://neuroimage.usc.edu/brainstorm/Tutorials/Epoching#On_the_hard_drive
- Or from a time series figure opened simultaneously: make sure the montage applied in the two figures ("3D electrodes" and "time series") is the same, the values displayed under the cursor are the ones you want. Right-click on the time series figure > File > Export to...
If you know exactly what time point you are interested in, you could even extract it first with the process Extract > Extract time or a right-click > Import in database, this way you would not have to deal with finding the appropriate time index.
From tutorial 5, I read this statement "A simple inverse problem + forward problem are solved to reconstruct the magnetic fields on a high-resolution surface".
This is exclusively for reconstructing MEG topographies.
In the case of SEEG and ECOG, with the display mode 3D electrodes, you get a direct access to the recordings (with optionally a montage applied)
