Dear FreeSurfer Experts and Users,
This is probably a basic question, so please bear with me.
I'm looking at the Coronal view in tkmedit, and I am wondering how does FreeSurfer knows where a gyrus ends and a sulcus begins (and vice versa).
For example, I'm looking at the superior temporal sulcus. But I'm not sure how FS figures out which part is superior temporal gyrus, middle temporal gyrus, or superior temporal sulcus?
Thanks! Daniel
Hi Daniel
we have had various neuroanatomists make that decision, but the typical measure used is the average convexity or sulc (stored in ?h.sulc). Where it crosses 0 is where the changeover is usually deemed to be
cheers Bruce
On Mon, 22 Apr 2013, Yang, Daniel wrote:
Dear FreeSurfer Experts and Users,
This is probably a basic question, so please bear with me.
I'm looking at the Coronal view in tkmedit, and I am wondering how does FreeSurfer knows where a gyrus ends and a sulcus begins (and vice versa).
For example, I'm looking at the superior temporal sulcus. But I'm not sure how FS figures out which part is superior temporal gyrus, middle temporal gyrus, or superior temporal sulcus?
Thanks! Daniel
Thanks, Bruce!
The average-convexity-crossing-zero idea makes good sense.
Also I can see the segmentation/parcellation label in tkmedit when I move my cursor. That makes it clear which label is which.
Best, Daniel
Hi Daniel
for the aparc.a2009 atlas :
- The average convexity sulco-gyral threshold vas usually set to 0 for the lateral cortex, and to 0.18 for the medial cortex.
- The average convexity value was negative for the whole insula (located deeply in the lateral sulcus/fossa). For the insular region, we used the mean curvature in a similar way: vertices with a positive mean curvature value were considered sulcal, and vertices with non positivevalues were considered gyral.
for more detail you can have a look to Destrieux C, Fischl B, Dale A, Halgren E. Automatic parcellation of human cortical gyri and sulci using standard anatomical nomenclature. Neuroimage 2010; 53: 1-15.
cheers
freesurfer@nmr.mgh.harvard.edu
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Bruce Fischl -
Christophe Destrieux -
Yang, Daniel