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For a VolumeAnalysis [fwhm]=8 or 6 is typical. For a SphericalAnalysis, it is common to apply minimal smoothing ([fwhm]=2) in VolumeSpace and then apply additional smoothing in SphericalSpace using FsFastSphericalSmooth. See EffectsOfSmoothing for a discussion of the consequences of smoothing in both VolumeSpace and SphericalSpace.