There are established ways to address these questions: we can assess unusual movements, analyze changes in mood and thinking, and take images of the brain areas involved in HD. (en.hdbuzz.net)
The scanner creates images of the brain by generating an intense magnetic field. (discovermagazine.com)
But since they're looking at images of your brain on a monitor, it seems like there is no way they would miss what you just felt. (discovermagazine.com)