I've recently found a problem with the left hemi of fsaverage. This problem unfortunately also extends to the left hemi of any average subject created with stable3. The right hemi is not affected.
The problem was that the lh.sphere.reg was wrong (it was actually that of average7). This will cause some inaccuracies in the visualization of maps on the left hemi of fsaverage and other average subjects (but the statistics themselves should be ok).
I've included jpegs of the cortical parcellations on the left hemi as they should be ("good") and as they are with the incorrect lh.sphere.reg ("bad"). The parcellations are not dramatically different, but the boundaries do shift around a bit, especially medially.
I have fixed this error in stable, and the fix will be live upon the next stable update. It is already live in dev. Nick is also preparing a new tarball for distribution, and this will include this fix.
If you have an average subject that you want to correct, you do not have to rebuild it. Rather, you can simply:
cd youraveragesubject/surf cp lh.sphere.reg lh.sphere.reg.old # backup cp rh.sphere.reg lh.sphere.reg # copy rh.sphere to lh.sphere
There should be no difference between lh.sphere.reg, lh.sphere, rh.sphere.reg, and rh.sphere (they are all 7th order icosahedron).
If in the future, if you need to determine whether an average subject has the correct sphere.reg, just use the unix diff command to check for differences between lh.sphere.reg and rh.sphere.reg.
I'm sorry that this error occured, and I hope it does not cause too much inconvenience. Please contact me if you have any questions.
doug
