https://sites.utdallas.edu/fas/#:~:text=Foreign%20accent%20syndrome%20(FAS)%20is,stroke%20or%20traumatic%20brain%20injury.

Sarah Colwill and others:

https://www.youtube.com/watch?v=ZCYGI0LvQws

Studies that suggest FAS may be more of a psychological issue:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4846654/