The neural basis of Charles Bonnet hallucinations: a hypothesis

Objectives: To describe the hallucinations occurring as a result of a macular hole in each eye and to investigate the neural basis. Methods: Psychophysical observations including sketches of the hallucinations calibrated for size. Results: All the hallucinations were of the geometric (patterned) type and lasted for only a few days. Conclusions: The observations can be explained on the basis of a “deafferentation” model, which is described in some detail. It is proposed that the hallucinations result from activation of the “blobs” of area V1 and the “stripes” of area V2 in the visual cortex. A theory is proposed to account for the disappearance of the hallucinations by a “filling in” mechanism.