The conditions include Parkinson's disease, fever, intoxication, and visual loss. For example, a surgeon and amateur pianist who was losing vision from macular degeneration started seeing musical notations, "just like a sheet of real music." A man with Parkinson's disease and a gifted pianist started seeing staves and lines of music on the pages of books he was reading.
Although the brain mechanisms that create visual hallucinations of musical notation are not known, they may involve the left inferotemporal cortex, which is crucial for the act of reading, and perhaps also the parietal lobes, which are known to be involved in reading musical scores, Sacks speculates.
Visual hallucinations are, of course, not limited to music. For instance, when seniors suddenly start seeing images of adults or children whose identity is not known and who do not speak, it should arouse suspicion of the presence of Lewy body disease, according to Myron Weiner, M.D., a clinical professor of psychiatry and neurology at the University of Texas Southwestern Medical Center. For more information about this subject, see Psychiatric News.