This video shows how echo planar imaging (EPI) scans are acquired in functional magnetic resonance imaging (fMRI) scanners. EPI scans are the most common type of scan used in human brain research.
This illusion shows how the boundaries of an object affect your perception of the 3D shape of the object. Notice how the number of bumps seem to change as the boundaries change, even though the shading is the same throughout! This shows that shading alone isn’t sufficient to tell you what is convex and what is concave – the final 3D percept depends on BOTH the shading and the boundaries of an object.