Hi Greg, I don't know what "areal expansion" refers to. If you want to use area (eg, the area tab in qdec), you should make sure to download the most recent version of mris_preproc (which performs a jacobian type correction) ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/mris_preproc doug
On 08/21/2012 04:59 PM, Gregory Kirk wrote:
Hi folks, I wanted to make sure i have everything straight w.r.t. the surface area measures.
as i see there are 4 ways implemented ( somewhere ) to do cortical surface area analysis.
areal expansion
Local Gyrification Index
direct vertex based true surface area glm, Winkler AM et. al
roi based, i.e. based on the surface areas of the parcellation units in lh.aparc.a2009s.stats etc.
recent pub, Lisa T. Eyler et. al used the areal expansion method.
was this done exactly as would be achived by using the area tab on qdec and setting up a glm ? Dale published surface area specifying some details of implementation but i was not sure if this was exactly what is implemented in qdec ?
- LGI seems to me this is the ratio of two areas, that of the hull to the area inscribed by projecting
the border of the hull onto the grey/white surface. In an e-mail Nick said LGI is a curvature based measure and that confused me a bit. gyrification is of course related to curvature but it seems the quantities actually calculated here are ratios of areas, which gives local info on surface area differences.
the winkler stuff is i think not publicly available yet at this time ?
straightforward enough not withstanding ICV corrections, etc.
any words of clarification before i start trying some analysis on my group ?
thank you
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