Memory is a mysterious thing. A few years ago my grandmother had a series of strokes and dementia set in. She's a polyglot, she speaks seven languages. But suddenly, post stroke she started speaking a mixture of Polish and Russian -- two languages that my family doesn't speak. She's stuck in this linguistic fog and nobody in my family can find our way through. And I wondered why does the brain latch on to one language and not another? This week on the World in Words podcast we delve into dementia and bilingualism. I speak with two scientists Ellen Bialystok a psychology professor at York University in Canada and Thomas Bak a neuropsychologist at the University of Edinburgh about their research into dementia and bilingualism. You’ll also get to hear from the expert, my grandmother, and hear a bit of my own crackpot theory as to why she’s chosen to speak Polish and Russian.