A picture created by the imagination with no visual stimulus required.
Mental images are created by the brain from memories, imagination, or a combination of both. In the 1990s, scientists were gaining knowledge of how the brain forms these visual pictures without input from the eyes. According to researchers at Harvard University, the brain may generate these mental pictures in the area of the brain responsible for vision. Stephen Kosslyn, a psychologist, used positron emission tomography (PET) technology to examine the flow of blood in the brains of twelve men. The men were asked to close their eyes and imagine total darkness. Subsequently, they were asked to imagine a series of different items. The tests seem to indicate that the primary visual cortex, the area of the brain that interprets vision, was activated when creating the imagined images.
Bower, Bruce. "Brain Scans Set Sights on Mind's Eye." Science News (December 2, 1995): 372.