Dear experts, I am studying a group of patients with a genetic illness that implies alterations of olfactory tracts and sulci. My aim was to explore the depth of the olfactory sulci in both patients and controls. I draw a ROI following the image of the sulcus in the fsaverage (see the figure) and I extracted measures of 'sulc' and 'thickness' for any subject using this ROI.
My problem is that I found only zero or negative values for sulc (also in controls!). This means that there is not a sulcus, but a gyrus? The difference is statistically significant between patients (more negative) and controls (around zero or low negative).
What is the problem and how can I measure the depth of the sulcus? Perhaps should I work on an 'average' surface based on my healthy controls? How can I obtain it?
Thank you for any help!
Angela