Figure 6.

Imposing an arbitrary ‘extent threshold’ based on the number of contiguous activated voxels does not necessarily solve the problem of false positives. (Top) Using the same activation map as in the previous simulations, spatially correlated noise at three different levels of smoothness was added, and the corresponding t-maps were generated. (Bottom) These maps were thresholded at α=0.10. Due to the inherent smoothness of the image, the false-positives (outside of the squares) tend to be contiguous regions of multiple voxels that can easily be misinterpreted as regions of activity.