Can’t hear at noisy parties? Blame a busy brain!

LOTS of friends and family descended on our house over Christmas, and while a good time was had by all, ‘good time’, as far as my kids are concerned, involves talking very loudly, all at once, and I often struggled to follow the conversation.

I’d always assumed that this common problem was because of age-related damage to the hair cells that transmit messages about sound to our brains. But it turns out something else is also going on: with age, parts of our brains are simply too active.

Normally, when you hear a sound, some brain cells become more active, while others become less active so you can really focus. However, as we get older, we’re not as good at turning off particular cells, so it’s harder for our brains to focus on one type of sound — e.g. someone talking to you — while simultaneously filtering out surrounding noise.

This new insight comes from mice studies at Johns Hopkins University. The U.S. researchers taught mice to lick a water spout when they heard a particular tone. Then they did the same thing while playing a loud background noise. Without the background noise, older mice licked the water spout just as enthusiastically as young ones when they heard the tone.

But when the extra noise was introduced, the older mice got confused about when to lick the spout. And scans showed that was because critical cells in their brains that were supposed to turn off, hadn’t.

This may help explain what happened when I was filming last summer with an 86-year-old jazz trumpeter called Bobby Lewis. Despite the fact that he’s a good 20 years older than me, tests showed his brain was better at distinguishing sounds against a jumble of background noise. It seems years of playing improvised jazz had taught his brain to focus on specific sounds and filter out the rest, just like those young mice. The mouse study researchers say their findings suggest ‘there may be ways to train the brain to focus on individual sound amid a cacophony of noise’. In the meantime, I’ll have to keep reminding my children to use an ‘indoor’ voice when we gather, and perhaps also start flicking through hearing aid ads.