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A number of mental disorders comprise aberrant perceptions that are often described as possessing a perceptual quality approaching real-life sensory experience, while at the same time lacking a sensory correlate in the real world. Healthy individuals can also have perceptual experience without an external correlate when they engage in mental imagery. Aberrant perceptions differ from mental imagery in their lack of voluntary control and the sense of reality. Early theories suggested that increased imagery vividness could lead to aberrant perceptions in a number of clinical disorders. However, cognitive and neuroimaging studies do not endorse this view, and instead suggest that mental imagery comprises a functional architecture that is at least partly shared with memory and perception. Miscommunication or disconnection between brain areas or functional modules within this architecture may give rise to aberrant perceptions and their sense of reality. We describe the evidence for this view in relation to psychotic hallucinations in schizophrenia, hallucinations in neurodegenerative disorders and flashbacks of traumatic events in post-traumatic stress disorder. We suggest that an impaired neural architecture of imagery, rather than merely increased intensity or vividness of imagery, underlies aberrant perceptions. This view fits with neurobiological models of mental disorders that suggest that psychopathological symptoms arise from disrupted communication between brain areas.