# Still-high spatial resolution of (smoothed) fMRI activation clusters!

There appears to be a mismatch between how fMRI results are presented graphically and how we know the analyses are normally done.

Say we do a group-level analysis for some contrast of interest, and we thus obtain voxelwise t-values that we plot in a typical 'brain activation' map. Prior to the analysis however, the images typically undergo Gaussian smoothing (blurring), and this would mean that the voxelwise information is itself only as spatially-accurate as the images were after they were smoothed.

This would mean, their spatial resolution should be considerably lower than that of an anatomical (T1-weighted) image. Indeed, in many statistical-parametric-maps, the activated voxels do appear of a lower resolution, but in some (see below) they seem to be of the same resolution as the unsmoothed voxels around them (normally: 1mm). How can this be? Is it an error on the part of the scientists who make these plots, or a glitch in my understanding of how smoothing is done in fMRI analyses?