Silence Your Brain!

Peter was after a talking parrot, so he went to the local pet shop in the hope of securing such a find. He was in luck. The shop assistant assured her that the parrot would learn and repeat any word or phrase it heard. Peter was delighted. However, a week later, the parrot still hadn’t spoken a word. Peter returned to the shop to complain, however, it appeared that the assistant was accurate in what he had said and refused a refund. Why didn’t the parrot talk? [answer at the end, but remember the parrot repeats every single word it hears].

Shut up! Like the mute button on the TV remote control, our brains filter out unwanted noise so we can focus on what we’re listening to. Most of us will be familiar with the experience of silently talking to ourselves in our head. That inner monologue usually conducted in silence. Self doubts, insecurities and a general soundtrack or commentary to life.

Have you ever been at the supermarket and realise that you’ve forgotten to pick up something you needed. You might say (outloud), ‘saugages!’ or whatever your temperoary lapse of recall was. Or maybe you have got an important meeting with your boss later in the day, and you’re simulating, (silently in your head) how you think the conversation might go, possibly hearing both your own voice and your boss’s voice responding. This is the phenomenon that psychologists call inner speech, and they’ve been trying to study it pretty much since the dawn of psychology as a scientific discipline.

Our Brain’s have a built in filter for unwanted noise. When it comes to following our own speech, a new brain study from the University of California, Berkeley, shows that instead of one homogenous mute button, we have a network of volume settings that can selectively silence and amplify the sounds we make and hear. They discovered that neurones in one part of the patients’ hearing mechanism were dimmed when they talked, while neurones in other parts lit up. Their findings, published in the Journal of Neuroscience, offer clues about how we hear ourselves above the noise of our surroundings and monitor what we say. Previous studies have shown a selective auditory system in monkeys that can amplify their self-produced mating, food and danger alert calls, but until this latest study, it was not clear how the human auditory system is wired.

With this in mind it might make more sense when we need to really listen to something that is important. Say you have to listen to fill a prescription or enter data that is potentially life threatening if you get it wrong. When we want to listen carefully to someone, the first thing we do is stop talking. The second more surprising thing we do is stop moving altogether. This strategy helps us hear better by preventing unwanted sounds generated by our own movements.

This interplay between movement and hearing also has a counterpart deep in the brain. Indeed, indirect evidence has long suggested that the brain’s motor cortex, which controls movement, somehow influences the auditory cortex, which gives rise to our conscious perception of sound. A new study, in Nature, combines cutting-edge methods in electrophysiology, optogenetics and behavioural analysis to reveal exactly how the motor cortex, seemingly in anticipation of movement, can tweak the volume control in the auditory cortex. The findings contribute to the basic knowledge of how communication between the brain’s motor and auditory cortexes might affect hearing during speech or musical performance.

And the parrot? The parrot was deaf. Therefore it couldn’t repeat a single word it had heard – as it had heard no words at all.

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