Hi everyone, I am writing for a brief question. I want to invert the activity at the source level (PSD) from the left hemisphere to right one and viceversa. As a first step I found the vertices belonging to the left and to right hemisphere with the function tess_hemisplit. I'm using the default anatomy. In this way I found that all the vertices from the 1:7501 belong to the left hemisphere, and from 7502:15002 to the right one. Then, I simply changed the value in the TF matrix so that the rows from 1:7501 are filled with the value of the rows from 7502:15002, and viceversa. However the results is messy and not the inversion of the activity from one hemisphere to another. What am I doing wrong? Any suggestion?
Thanks
Unfortunately, there is no way to have symmetrical projections between hemispheres. The spherical registration performed by FreeSurfer allows to project source maps between different brains registered on the FSAverage subject, but the left and right spheres are not necessarily symmetrical.
The only thing I can suggest to compare left/right source maps is to work at a ROI-level using a parcellation that defines the same regions on both sides.
Oh I see, I erroneously assumed a simmetry between hemisphere vertices. Good to know!
Thanks!