Sir Terry films Alzheimer's battle
Sir Terry Pratchett will expose the perils of "snake oil peddlers" in a hard-hitting documentary on treatments for Alzheimer's.
The award-winning author, who was diagnosed with the condition at 59, continues his battle to show how dementia sufferers are treated as "superfluous old farts" in the new film.
His campaigning for the Alzheimer's Research Trust has inspired £200,000 of donations on top of the £500,000 he has already pledged, a spokesman for the charity said.
Sir Terry, who has a particular strain of Alzheimer's called Posterior Cortical Atrophy (PCA), has been trialling a new device that claims to slow, and even reverse, the effects.
The documentary, to be screened in two parts on BBC2 on February 4 and 11, follows Sir Terry as he learns about the work of scientists searching for a cure.
Professor Simon Lovestone, one of the scientists who will feature on the programme, said: "It is vital that the public understands the importance of dementia research.
"Through his candid and positive response to his diagnosis, Sir Terry has been a great help in bringing scientists and the public together in our fight against dementia. He has not only raised awareness of dementia research, but also inspired many scientists working in the field."
The award-winning author, who was diagnosed with dementia in 2007, is one of the first patients in the UK to try the anti-dementia helmet.
The device sends intense bursts of light at a particular wavelength into a patient's skull.
The 60-year-old is a staunch campaigner for Alzheimer's sufferers, and recently handed a petition to Downing Street calling for an increase in funding for dementia research. Sir Terry said at the time that the issue was "a matter of urgency".
Terry Pratchett in 2005 
The ''Discworld'' author Sir Terry Pratchett is to appear in a BBC documentary covering a year of his struggle with the brain disorder Alzheimer's disease.

Pratchett, 60, asked the BBC to spend a year documenting any decline in his condition and seeing him experiment with various supposed cures. One alleged cure involved firing infrared light at his brain via a helmet invented by a general practitioner doctor. Pratchett also examines the serious research into dementia and its cure.

The author has donated £500,000 to the Alzheimer's Research Trust and his campaigning has raised another £200,000. Pratchett has posterior cortical atrophy, a rare form of the disease which affects vision, causes him to forget words and makes dressing confusing. He has written 36 ''Discworld'' novels amongst other works and was knighted in the 2009 New Years Honours.

Posterior cortical atrophy is also known as Benson's syndrome. It is the progressive shrinking of the back of the brain. It is a form of Alzheimer's disease, and the wider disease affects some 26.6 million people worldwide.

The documentary - ''Terry Pratchett: Living with Alzheimer's'' - will air on BBC Two on February 4 at 21:00.