New Delhi, March 10 -- 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.

"It's pretty brutal," Worthy said of her rare neurological condition. "I'm starting to lose everything, you know, and this is really rewarding and seeing all these people, yeah, it did make me have a lot of memories."

She was taking part in a so-called "singing circle" run by opera singer Maartje de Lint at the landmar...