"Foreign accent syndrome is a speech disorder that is completely in the ear of the listener," said Fridriksson. "So, people from different backgrounds will hear different accents."
When researchers closely examined Dore, they noted -- with the help of family members -- that the overall pacing of her speech had slowed down and she pronounced vowels differently than before the stroke.
Researchers took acoustic measurements of Dore's vowel sounds and found they compared closely but not exactly to the vowel sounds made by East Coast Canadians.
"It's not exactly a true accent," said Dr. Karin Humphreys, one of the researchers who worked with Dore and reported the case in the Canadian Journal of Neurological Sciences.
Humphreys likens Dore's new foreign accent to a trained musician playing an instrument a little out of tune.
"We're all virtuosos at speaking," said Humphreys. "If you do just a slight detuning ... it's going to shift the system around."
Humphreys, an assistant professor of psychology, neuroscience and behavior at McMaster University in Ontario, noted other linguistic differences as well: "The consonants changed, so she was [saying] 'dat' and 'dis' instead of 'that' and 'this."
What was especially interesting to researchers was that Dore still made the "th" sound on occasion, so she was clearly capable of doing so. This indicated to Humphreys that the change with Dore's speech wasn't caused by a malfunction with the muscles that moved her mouth and tongue. Instead, the problem existed in how her brain was instructing those muscles to act.
Still, the exact cause of foreign accent syndrome is not clear. Humphreys said the stroke probably affected Dore's basal ganglia -- an area deep in the brain that's involved in controlling movements. Previous research has linked the basal ganglia to speech problems such as stuttering.
"That's what we think is the most important thing going on here," said Humphreys. "This makes sense. It's all part of the speech motor circuit."
Fridriksson's patient also had brain damage in the basal ganglia.
And in addition to providing a window into how the brain plans speech, the syndrome also allows researchers to examine how the brain recovers after a stroke.
"When you have very small brain damage, the rest of the brain can sort of compensate in the long run and help you get better," said Fridriksson, whose patient in South Carolina eventually lost his French accent.
Now two years after the stroke, Rosemarie Dore still has trouble walking and can't use her right hand. The accent is still there, though she doesn't notice it anymore. In some ways, it's the least of her concerns these days: "There are some people that can't talk at all [after a stroke]. I talk, but it's different."