linguistics quirk, "foreign accent syndrome"

wherein a damage suffered to a specific spot in the language processing region results in systematic shifts in vocal production so that the person gives the impression of speaking with a foreign accent:
 
http://www.npr.org/blogs/health/2011/06/01/136824428/a-curious-case-of-foreign-accent-syndrome
 
[excerpt]
When Karen Butler went in for dental surgery, she left with more than numb gums: She also picked up a pronounced foreign accent. It wasn't a fluke, or a joke — she'd developed a rare condition called foreign accent syndrome that's usually caused by an injury to the part of the brain that controls speech.
 
Butler was born in Bloomington, Ill., and moved to Oregon when she was a baby. She's never traveled to Europe or lived in a foreign country — she's an American, she says, "born and bred."