Charles Bonnet syndrome
Patients who become visually impaired often develop complex hallucinations (i.e., visual hallucinations with preserved insight) with preserved cognitive status,
A parallel phenomenon is the emergence of hallucination, including musical hallucinations in individuals with acquired deafness.
These observations suggest a “supersensitivity deprivation” hypothesis that, when deprived of important and anticipated perceptual stimuli, the mental apparatus may overinterpret any sensory stimulation as evidence of the presence of the needed objects.