AMSTERDAM — Megan Worthy still recalls singing in a choir in the Australian capital, Canberra, as she was growing up.

Now, as a rare form of early-onset dementia chips away at her vision and other brain functions, the 58-year-old is transported back to her musical youth as she and her daughter, Bronte, sing together with other people with neurological conditions in an Amsterdam concert hall, the Concertgebouw.