A hand with its own mind is not just film fantasy

Even today, "anarchic hand" has earned the popular sobriquet Dr Strangelove syndrome - named after the eponymous scientist with the unruly limb in Stanley Kubrick's 1964 film.

Just like Peter Sellers' character in the movie, the 40 or so people with anarchic hand in real life are often forced into pitched battles with the appendage.

Professor Sergio Della Sala, of the University of Aberdeen, says one of his patients regularly tries to strangle himself at night.

Talking at the British Association's Festival of Science this week, he said the condition was caused by damage to a certain area of the brain.

Pointing the way

That a stroke, head injury or aneurysm can cause a hand to become errant in this manner raises questions about how all our brains operate.

Examining Dr Strangelove syndrome may help us answer some of these intriguing questions of human free will, says Professor Della Sala.

The type of brain damage which leads to anarchic hand is also blamed for a range of unusual afflictions.

Foreign accent syndrome is an incredibly rare condition, with just a handful of cases ever reported in the UK.

"Funny, I wasn't Scottish last night."

"The person appears to be speaking in either an accent change or they sound as if they are a speaker of another language," said language therapist Dr Karen Bryan in 1997, when London-born Annie Bristow began to talk with first a French and then Scottish lilt.

Patients like Mrs Bristow, who had a haemorrhage followed by a stroke, experience a change in their speech patterns causing them to enunciate words differently, despite their efforts to talk normally.

Although not the same as foreign accent syndrome, some people suffering asphasia - a change to their understanding of speech - revert to modes of communicating they used in the past.

Tongue tied

This condition is most noticeable in immigrants who have all but forgotten their mother tongue.

In a letter to The Times, following the case of a Scots woman who began speaking in a South African accent, Dr BI Chazan recounted the tale of a Jewish refugee from Nazi Germany who decided to speak only in modern Hebrew on reaching Israel.

Three decades on, a stroke robbed the man of his Hebrew, leaving him the "preserved ability" to speak the German he had disavowed.

The inability to recognise familiar objects and people is another hallmark of these uncommon syndromes.

Agnosia can leave people unable to recognise once familiar sights

Landmark agnosia leaves sufferers unable to distinguish large objects, such as buildings, in once familiar surroundings.

Though able to describe a journey before setting out and notice small details, such as doorknobs on the houses they pass, sufferers cannot memorise the structures the rest of us use as signposts.

"They'll turn a corner and the street will be completely unfamiliar to them," said Dr Geoffrey Aguirre, a neuroscientist at the University of Pennsylvania.

Looks unfamiliar

Similar agnosias render people unable to recognise faces, shapes or even specific sorts of animals.

Supposedly the rarest of these types of conditions, and arguably the most distressing, is Capgras syndrome.

Named after the French doctors who identified it in the 1920s, the syndrome causes its victims to conclude a loved one has been replaced by an impostor.

It results from the breaking of the link between the parts of the brain responsible for visual recognition and emotional response, brought on by a head injury or a deep depression.

Capgras syndrome sufferers believe loved ones are replaced by impostors

In 1995, a Welsh couple were involved in a minor car crash. Alan Davies became convinced by a series of vivid flashbacks that his wife of 31 years had not survived the accident.

He decided that Christine Davies, suffering nothing more than whiplash, was a double impersonating his "dead" spouse.

Though Mr Davies still believes that "Christine One" was killed, and shows little affection for her "double", the couple have not divorced.