Hello, We have observed several instances now where the surfaces around the insula are incorrectly constructed, with the pial surface being pulled inward toward the putamen. The likely source of this problem is that there is no obvious white matter between the putamen and insular cortex.
Based on a previous suggestion, we tried editing the aseg to add a thin strip of putative white matter between the labels for the putamen and cortex, but this didn't prevent the problem. jpegs of the brainmask, aseg, and wm volumes are attached to illustrate. These data were processed using FS v4.0.1, EXCEPT that we used the most recent development version of mris_make_surfaces (v 1.105, built 11/2/2007) that we could find at the ftp site.
Two questions: 1) Should we be concerned about fixing this type of pial surface problem in the insular cortex? (i.e., since this region typically seems to get labelled as 'unknown' in the aparc parcellation should we just ignore defects of this type?)
2) What controls the degree to which the ?h.white surfaces are allowed to deviate from the ?h.orig surfaces? In particular, while the orig surface is reasonable for this brain in the putamen/insular region (because it follows wm.mgz, which we can edit if need be), the putative white surface is too medial. The notes in 'recon-all' for the 'finalsurfs' stage state that "The white surface is created by "nudging" the orig surface so that it closely follows the white-gray intensity gradient as found in the T1 volume". How does one prevent the white surface from being "nudged" too far away from the orig surface, as occurred for this brain?
thanks, Mike Harms
