Neurosurgeon says he rode butterflies in heaven.

A Harvard neurosurgeon has said that heaven exists after he came out of a seven-day coma where the "human" part of his brain was deactivated.

Dr Eben Alexander said that his near-death experience had convinced him that heaven was real, Newsweek reported. In his book, Proof of Heaven, he argues: "God and the soul are real and death is not the end of personal existence but only a transition."

Alexander explains that, as a neurosurgeon, he has always questioned people who claim to have had near-death experiences because there is a rational scientific explanation for such feelings.

Researchers from Edinburgh University and the Medical Research Council in Cambridge backed his earlier assertions and said that most experiences could be put down to reactions in the brain.

So-called out-of-body experiences, for example, happen when there is a breakdown of multisensory processes, they said. Well-documented visions of tunnels and bright lights could be the result of oxygen deprivation.

But Alexander has rebutted his own beliefs after he fell into a coma as a result of an attack by the E. coli bacteria in 2008. He says he now has scientific proof that heaven exists.

He writes: "There is no scientific explanation for the fact that while my body lay in coma, my mind - my conscious, inner self - was alive and well.

"While the neurons of my cortex were stunned to complete inactivity by the bacteria that had attacked them, my brain-free consciousness journeyed to another, larger dimension of the universe: a dimension I'd never dreamed existed and which the old, pre-coma me would have been more than happy to explain was a simple impossibility."

He said of his journey to the other side: "For most of my journey, someone else was with me. A woman. She was young, and I remember what she looked like in complete detail. She had high cheekbones and deep-blue eyes. Golden brown tresses framed her lovely face.

"When first I saw her, we were riding along together on an intricately patterned surface, which after a moment I recognised as the wing of a butterfly.

"Without using any words, she spoke to me. The message went through me like a wind, and I instantly understood that it was true. I knew so in the same way that I knew that the world around us was real - was not some fantasy, passing and insubstantial."