Foreign accent syndrome (FAS) is a neurological condition that is acquired following a stroke or some other form of brain injury. It occurs as a result of damage to the brain's speech motor centres, so that syllables are mispronounced, making one sound as if they are speaking their native language in a foreign accent.

FAS is extremely rare, with only around 50 reported cases since 1941. Two of these were reported in stroke victims in recent years: Linda Walker, a 62-year-old woman from Newcastle, began speaking in an accent that was described as a mixture of Jamaican, Canadian and Slovakian, whereas Tiffany Roberts, a 63-year-old American, began speaking in what sounds like a British accent.

Neurologists from Toronto now report the first Canadian case study of the condition. Writing in this month's issue of the Canadian Journal of Neurological Sciences, Naidoo et al describe the case of a stroke patient named Rosemary Dore, who previously had a native Southern Ontario accent, but is now speaking with an East Coast Canadian accent, despite never having lived in that part of the country.

The authors of the study told journalists:

Instead of saying 'that' and 'this' she was saying 'dat' and 'diss' at least some of the time. So the 'ths' were turning into 'ds' and 'ts' and her vowels were really changing so they were getting really elongated.

While the new accent was apparent to the woman's family, the woman could not detect the changes herself. Despite intensive speech therapy, the new accent persists, even two years later.

Her speech is perfectly clear, unlike most stroke victims who have damage to speech-motor areas of the brain. You wouldn't guess that the speech changes are the result of a stroke.

Most people meeting her for the first time assume she is from out East. What we are seeing in this case is a change in some of the very precise mechanisms of speech-motor planning in the brain's circuitry.