Hello Freesurfer Experts, Recently there were two article published regarding clusterwise simulations for volumetric fmri analyses and potential errors for underestimating clusterwise extent thresholds.
1) http://www.pnas.org/content/113/28/7900.full.pdf?with-ds=yes 2) biorxiv.org/content/early/2016/07/26/065862 One issue pointed out from these articles seems software specific, however the second issue is determining the proper clustersize. The heavy-tail nature of spatial smoothness seems to be ignored and a gaussian shape is generally assumed, leading to an underestimation of the spatial smoothness which can affect cluster size calculations. The issues are highlighted in the second article above. I created my own monte carlo simulation in Freesurfer for a specific brain template and I wanted to find out if these concerns also apply to my surface based simulations? I am not sure if it does since the monte carlo tool is a GRF simulation as opposed to an analytic equation, however given that these articles were highlighted very recently, I wanted to ensure I am running things appropriately for surface based cortical thickness/dti analyses. Thanks, Ajay
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