'A VOICE IN YOUR HEAD?' : SCIENCE MASTER PRECIS

 

A voice in your head? : It could be your own. Scientists see the possibility of understanding what is behind your hallucinations.

Few people like hearing their own voices on recordings. The voice sounds fake, as if it belongs to someone else.

For neuroscientists, that quality of otherness is more than a curiosity. There are many mysteries about the origins of hallucinations, but one hypothesis suggests when people hear voices, they are hearing their own thoughts registered by the brain as the voice of another person.

Scientists would like to understand what parts of the brain allow us to recognise ourselves speaking, but studying this using recordings of people's own voices has proved tricky.

When we talk, we not only hear our voices with our ears, but on some level we feel the sound as the vibrations travel through the bones of the skull.

In a study in the journal Royal Society Open Science, researchers investigated whether people could more accurately recognise their voices if they wore bone conduction headphones, which transmit sound via vibration.

They found that sending a recording through facial bones made it easier for people to distinguish their voices from those of strangers.

Recordings of our voices tend to sound higher than we expect, said Pavo Orepic, a postdoctoral researcher at the Swiss Federal Institute of Technology who led the study. The vibration of the skull makes your voice sound deeper to yourself than a listener.

The team recorded volunteers saying the syllable ''ah'' and then blended each recording with other voices. They had some subjects listed with bone-conduction headphones, while others used regular headphones.

People with bone-conduction headphones were more likely to identify their own voices, the team found. That opens a door to understanding how one's brain takes this information and turns it into a recognition of one's self.

If scientists can understand how the brain builds the concept of self from sound, Dr. Orepic suggests, then perhaps they can unpack what is different in people who hear voices in their heads that are not their own.

The team is studying how people with portions of their brains removed - to treat drug-resistant epilepsy, for instance - perform on the task. The more surgery disturbs the brain's self-recognition network, the harder the task of self-recognition becomes, he said.

For one patient, the test revealed a surprising pattern.

''Every time she heard her voice, she thought it was someone else,'' Dr. Orepic said. ''And when she hears someone else, she says, ''It's me.'' 

The World Students Society thanks author Veronique Greenwood.