How do our brains change as we get older? Noelle finds out, with the help of a neuroscientist, a centenarian, and a Poet Laureate.

Noelle McCarthy interviews Professor Richard Faull: watch the video here

Video filmed and edited by Diego Opatowski.

How do our brains change as we get older? Noelle McCarthy finds out, with the help of a neuroscientist, a centenarian, and a Poet Laureate.

CK Stead's writing career has continued unimpeded by age. Now 83, and having established himself as one of our best-known critics and most successful novelists, he's New Zealand's current Poet Laureate.

"I still seem able to write fiction and nonfiction. I hope if there is a decline, it'll be clear to me, or clear to someone else who will tell me, but so far I can't really detect it."

But he has noticed some change.

"Sometimes now, when I read a novel by Henry James, which when I was young I would have relished, and read easily, I'm now conscious of difficulty ... so there's a certain loss of intellectual edge, but there may be a compensating astuteness. I don't know, let's hope so!"

He was astonished when he reached 70 and is "bewildered" he's now 83.

"I'm very conscious of being old in a way I wasn't keenly aware of 10 years ago," he says.

"I'm starting to think about how one exits. There has to be an exit and it can't be too far away."

Our brains start growing just three weeks after conception and continue until early adulthood, when fully formed.

Professor Richard Faull, director of the Auckland Centre for Brain Research, says the brain shrinks by about 5 percent every decade after the age of 40.

But that doesn't mean we can't make new brain cells while we age, which Professor Faull and his team proved to the world in 2007. His team's discovery, based on research into Huntington's disease, debunked the received wisdom that we only lose brain cells as we get older.

Now we know that we can keep making new ones, even if we don't yet know how fast.

"Basically, the older you get the less ability you have to make new brain cells, and the question is we don't know how significant that is, but what we do know though is the more you keep people stimulated, doing things they like, living with people they love and enjoying life - having intellectual excitement and stimulation is good for the brain."…

Go to this episode on rnz.co.nz for more details