Hi Mahtab

you should look them up in a differential geometry textbook. Essentially, a 2D surface has two curvatures at each point, one in the direction of maximum folding (k1) and one in the direction of minimum folding (k2). The Gaussian curvature is then k1*k2 and the mean is (k1+k2)/2

cheers Bruce

On Wed, 6 Jul 2016, Mahtab Farahbakhsh wrote:

Dear FreeSurfer, I am using the mris_anatomical_stats output to calculate the curvature and thickness indices for different brain areas. However, I am not sure what the mean and gaussian curvatures mean. I could not find a complete description on these two. Would you please guide me what principle curvature and mean and gaussian curvatures means exactly?

I appreciate your concern in advance.

Best Regards, Mahtab.