Hi Allison,

A suggestion is to use the surface area of each hemisphere as the weighting factor. The global average thickness for both hemispheres is then given by:

bh.thickness = (lh.thickness*lh.surfarea + rh.thickness*rh.surfarea) / (lh.surfarea + rh.surfarea).

If you use the data in the ?h.aparc.stats, it already discounts the 'unknown' region, so you don't have to worry about that.

All the best,

Anderson

On 08/14/2011 06:12 PM, Allison R. Kaup wrote:

Hi all,

Please pardon the novice question... but what is the best way to get global mean cortical thickness (i.e. combined across hemispheres)? I have used mris_anatomical_stats to get mean thickness separately for each hemisphere. To get a global mean thickness, would I just take a simple average (RH mean thickness + LH mean thickness)/2? Or, do I need some sort of weighted average to account for hemispheric size diffferences? If so, what would I use as the weight?

Thanks! Allison