Speaking With A Sudden Foreign Accent
Some people wake up from a stroke or brain injury speaking their native language with a completely new accent. They never visited the region or learned the dialect, yet their speech patterns shift convincingly overnight.
This rare condition is known as foreign accent syndrome and usually results from damage to the areas of the brain that control speech production. It is not that the person has truly adopted a foreign tongue, but rather that changes in pitch and rhythm mimic the cadence of another culture. Listeners often project a specific origin onto the speaker, even if the sounds are just garbled by neurological trauma. It remains a fascinating look at how our brains calibrate the music of human language.
Source: Foreign accent syndrome