For grand-averaging, STC-files should have been created using the --morph option in mne_make_movie (see above). You can then average them using the command
mne_average_estimates --desc <descriptionfile.txt>
where descriptionfile.txt is of the form
stc /yourpath/filetoaverage1.stc stc /yourpath/filetoaverage2.stc stc /yourpath/filetoaverage3.stc deststc <youroutputfile>
You can create description files for every average you want to compute, and execute them in one script
# mne_average_estimates --desc <descriptionfile1.txt> mne_average_estimates --desc <descriptionfile2.txt> mne_average_estimates --desc <descriptionfile3.txt>
Reading, Writing, Subtracting STC-files
This simple Matlab script demonstrates how to read and manipulate STC-files.
data1 = mne_read_stc_file( STCfile1 ); % read STC-file 1 data2 = mne_read_stc_file( STCfile2 ); % read STC-file 2 data3 = data2; % data3 will contain subtracted data, but keep other information from STC-file 2 data3.data = data2.data - data1.data; % subtract STC-file 1 from STC-file 2 mne_write_stc_file( STCfile_out, data3 ); % Write subtracted data to STC-file
Examples of Current Estimates
These figures show MNE current estimates for a visually evoked brain response around 170 ms for a single participant. The left presents the unsigned (intensity), the right the signed version of the estimate. Note that the intensity version ignores the cirection of current flow on the cortical surface. In the signed version, the "speckled" pattern of positive and negative values most likely results from the fact that blurring of sources results in reversed directions of current flow on opposing walls of sulci.