Hi Angela
negative sulc implies gyral, but there must be positive sulc also, no? When you overlay sulc on an individual subject to you see red (positive) as well as green (negative)?
cheers Bruce
On Mon, 4 Feb 2013, angela.favaro@unipd.it wrote:
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