Mental imagery can be advantageous, unnecessary and even clinically disruptive. With methodological constraints now overcome, research has shown that visual imagery involves a network of brain areas from the frontal cortex to sensory areas, overlapping with the default mode network, and can function much like a weak version of afferent perception. Imagery vividness and strength range from completely absent (aphantasia) to photo-like (hyperphantasia). Both the anatomy and function of the primary visual cortex are related to visual imagery. The use of imagery as a tool has been linked to many compound cognitive processes and imagery plays both symptomatic and mechanistic roles in neurological and mental disorders and treatments.