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Dear Helmut, thank you very much for you help! No it is much clearer in my mind. Best, Tiago 2016-09-01 13:46 GMT-03:00 MRI More <[log in to unmask]>: > > as for the extent threshold (k), in the case of SVC on peak level should > we leave = 0? > With regard to k in combination with peak level correction, the k is > really an additional and arbitrary threshold. See > https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;4c8f7781.1402 and > responses. > > And finally and for sake of completeness, with regard to k in combination > with an uncorrected threshold, e.g. something like .001 and k > 10, please > see Bennett et al. (2009, https://dx.doi.org/10.1093/scan/nsp053 ): > > "Many authors justify this approach by referring to the results of Forman > et al. (1995), who examined clustering behavior of voxels in fMRI. The > results of Forman et al. suggest that a threshold of P < 0.001 combined > with a 10-voxel extent requirement should more than adequately control for > the prevalence of false positives. [...] The problem is that this threshold > is specific to the parameters of their dataset, and may be inappropriate in > other datasets. [...] The cluster size criteria can change quite > substantially from dataset to dataset." > > You will nonetheless also come across recent papers that refer to a > certain k from previous papers without proving that it was a good choice > for that study nor that it is a good choice for the current. > > Best > > Helmut > > > >