Hello everyone,
I am very new to FreeSurfer. Although I know what smoothing means etc. but I am not sure what smoothing level is the best to choose while comparing cortical thinning for patients vs. controls. Qdec gives several options to choose from among 0, 5, 10, 15, 20 and 25. Literature says 10 mm is the typical value to choose but when I calculate clusters, I don't see any significant clusters (at FDR p < 0.05) but at smoothing level 20 mm, I can see several clusters at the same threshold i.e. at FDR p < 0.05.
I would really appreciate if someone, expert in this field could guide me regarding this. Also, may be if someone could recommend me a few papers from literature discussing this issue e.g. effect of smoothing on cortical thickness etc., that would be very useful.
Thanks, MJ