Dear list,
I am trying to use freesurfer to visualise MEG data (minimum norm) overlayed on the cortical surface, both at an individual and group level. I have successfully processed all of the participants MRIs using recon-all, and have decimated the cortical surface (white) to compute the MEG solution. I would be grateful if anyone could help with the following issues I have run into:
1) I would like to know how to view the time-varying solution over the cortex using tksurfer. I have successfully exported the overlay for a single sample to a .w file (using matlab), and then smoothed it (mri_surf2surf) and viewed it on the cortical surface, which works great. But I am aware that .w format only supports a single 'frame' of data. Some previous posts on the list suggest that exporting the data in .mgh format as a nverts x 1 x 1 x nsamples volume would allow visualisation of the timecourse in tksurfer.
My question is: is there a way to only write out the data for the vertices with values (i.e. left after decimation) when using the mgh format, and not a matrix of the total vertices in the original cortex? For example, if the surface has N vertices, and after decimation I have M vertices left, using the .w format I only need to write out data for the M vertices, along with a list of the vertex numbers to place them on the original surface. Can I do this with .mgh? It is difficult to get matlab to write out an mgh file with a 140000x1x1x500 volume!
2) I wish to view the average data across several subjects, mapped onto the fsaverage subject template. I have seen that mris_preproc can warp one or more overlays onto a single subject. My question is: will mris_preproc work with the type of .mgh files I described above, i.e. containing multiple frames of data overlay? Or am I better trying to do the whole operation with .w files, with one per timepoint?
Many thanks in advance,
Padraig