SPM8

Dear Claus,

as you've noticed, SPM8's default is to report topological FDR results (peak- and cluster-FDR). This is described in: False discovery rate revisited: FDR and topological inference using Gaussian random fields. J. Chumbley and K.J. Friston, NeuroImage, 44(1):62-70, 2009. http://dx.doi.org/10.1016/j.neuroimage.2008.05.021 and in another manuscript under revision.

The height threshold you define during the Results procedure is the feature-inducing threshold (used to define local maxima and clusters). For topological FDR, I would typically choose "none" and a small T-value, for example 3. The MIP will display all voxels whose T-value is above 3 and the Results table will display all local maxima whose T-value is above 3 (actually, at most 3 local maxima per cluster, more than 8mm apart) and the corresponding FWE p-values and FDR q-values for peaks and clusters.

If you want to threshold the MIP to a particular significance level, go through the Results procedure again and enter the corresponding height and extent thresholds (the 0.05 critical thresholds are indicated at the bottom left of the Results table): (height) FWEp and FDRp for peak-FWE and -FDR. (extent) FWEc amd FDRc for cluster-FWE and -FDR.

I hope this helps, Guillaume.