I'm not sure I understand. Wouldn't any prediction result above statistical random (in the image mind reading study) be significant? If the study was performed correctly I don't really need to know much about fMRI to tell whether it's an interesting result or not.

The study misleading claimed to produce images from brainwaves. In reality, they effectively built a combination of classifier from brainwaves to one of a few predetermined classifications of images shown (still cool, but less impressive) and a neural net to reproduce images it was trained on given a classification (boring).