Hello Spharm experts, 

Thanks to your troubleshooting guidance along the way, I have successfully run a hippocampal analysis on 206 participants. Volumetric analyses of these data indicate a significant main effect of group on volume of the hippocampus. Running these data through SPHARM-PDM to localize which areas are driving these group differences show a main effect of group that is constrained in one hemisphere to the very tip of the tail. On the other hemisphere, effects are localized to the very tip of the head. Both clusters are rather small.

My question for you is - do these shape difference  indicate that the structural differences between the two groups are not localized to a specific subregion but are instead relatively large/global?

Many thanks in advance!
Lara

Hi Lara

To answer your question: there are 2 possibilities:
a) the shape differences are global, i.e. happening across the shape everywhere and as that means locally only a tiny change (which accumulates to a larger global change across the surface), your analysis did not pick that small change up.
b) the shape differences may be local, but not consistent. So that the subjects would show local, individual differences, that are not consistent within the group. i.e. some subjects in group A would have an enlarged head region and others and enlarged tail and again others an enlarged body region. You would see global size differences, but no local shape changes


Hope this helps
Martin

Great. Thank you!