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>The cluster-extent correction typically works in two steps: first >applying a height threshold (also known as the primary threshold, or >cluster-defining threshold), then second calculating corrected p-values >for the cluster extents formed at that height threshold. In the example >you presented, I imagine the primary threshold was p<0.01 (uncorrected, >based on T-map intensity) and the clusters were selected for having >corrected p-values p<0.05. Needless to say, these results probably >weren't generated by the combined extent-peak test of Poline et al. Uncorrected at p<0.01 and corrected at p<0.05 is a possible explanation. But in another map of this same paper, they also used a height and extent thresholds at p<0.001. In another paper, the author even used a joint height and extent threshold of p<0.0001. I think it's rare to use corrected p value at 0.0001, isn't it? >SPM by default produces and displays corrected and uncorrected p-values >for clusters and local maxima when you assess the results from an >analysis. Can anybody tell me how SPM calculates the corrected p-value? Thanks, Hong