Ananova:

Ghosts, night terrors and near-death experiences could be caused by a peculiar form of "blind-vision" often suffered by people who lose their sight.

Dr Dominic Ffytche said individuals who go blind through eye disease, or have their eyes removed, often report a bewildering and frightening array of hallucinations. They include abstract patterns and shapes but also disembodied faces and costumed figures.

In 60% of cases, patients reported seeing "grotesque" distorted faces with prominent eyes and teeth, said Dr Ffytche.

Forty per cent saw figures in costumes, including people in Edwardian clothes and Napoleonic uniforms, as well as knights in armour.

"They often wear hats and helmets," said Dr Ffytche, from the Institute of Psychiatry in London. Brain scans carried out while the patients were hallucinating showed activity in specialised regions of the visual cortex.

Speaking at the British Association Festival of Science at Imperial College, London, Dr Ffytche suggested that sightings of ghosts and other supernatural experiences could have the same biological cause.

Dr Ffytche pointed out that it is not always necessary to go blind to have these hallucinations. Strokes could trigger them off, as could having the eyes covered by patches for a sufficient length of time. The visions could also be summoned artificially, by electrical stimulation of the correct brain regions.