The two images on the previous page are identical - the image has simply been rotated by 180º. It is only one's experience and familiarity with the representations that can cause one's brain to interpret the images differently.
A slice of Brie, or cake is more commonly seen lying flat on a plate and viewed from above. Typically one's brian does not see a slice standing up on its end, but that would be an equally valid interpretation of the first image.