Science 3 min read

How our Brain Filters Sounds Using the Auditory Sensing Gate

Image courtesy of Shutterstock

Image courtesy of Shutterstock

Researchers at the University of Geneva, Switzerland explored how our brain filters sound using the auditory sensing gate.

In our current sound dense environment, you have to wonder how we’re able to maintain focus on specific sounds. Well, it turns out the brain has a filtering mechanism that allows us to focus on the essential elements.

For example, when two identical sounds pass through our ear, one of these filters – the auditory sensory gate – reduces the attention that the brain directs at the second sound.

However, people with schizophrenia seem to not have this ability. As a result, multiple auditory stimuli attack the brain, which disrupts the person’s attention capacity.

Based on this knowledge, health professionals developed a test, the P50, to diagnose the mental disorder.

According to a researcher in the Department of Basic Neurosciences in UNIGE’s Faculty of Medicine, Charles Quairiaux:

“The aim is to have the patient hear two identical sounds spaced 500 milliseconds apart. We then measure brain activity in response to these two sounds using an external encephalogram. If brain activity decreases when listening to the second sound, everything is okay. But if it’s almost identical, then that’s one of the best-known symptoms of schizophrenia.”

While this diagnostic method is widely accepted, how the auditory sensing gate works has remained a mystery, until now.

Thanks to a neuroscientists team from the University of Geneva, we now have insight into how our brain filters sound. According to their paper published in eNeuro, the filtering starts at the beginning of the auditory stimuli processing in the brainstem.

How the Auditory Sensing Gate Works

To test their hypothesis, the researchers placed external electroencephalographic electrodes on mice. Then, they subjected the rodents to the P50 test, varying the sound between two sounds per 125 milliseconds to 2 sounds per second.

As observed in humans, the brain activity of the mice decreased when listening to the second sound.

Next, the neuroscientists placed internal electrodes in the cortical and subcortical auditory regions of the brain, across the pathway for processing sound – the brainstem to the frontal cortex. They then administered the P50 test a second time.

The result showed that the drop in attention in response to the second sound occurred in the brainstem, not the frontal cortex as previously believed. In fact, the researchers noted a 60 percent drop in brain activity in this region of the brain.

Dr. Quairiaux points out:

“This discovery means we’re going to have to reconsider our understanding of the mechanism because it demonstrates that the filter effect begins at the very moment when the brain perceives the sound!”

So, how do the findings help people suffering from schizophrenia?

According to Quairiaux, the Geneva-based team has extended the study to mice with 22q11 deletion syndrome – a mutation that leads to schizophrenia in humans. That way, they can understand if the lack of filter occurs in the brainstem.

The researchers may be at the verge of discovering the source of one of the most common symptoms of schizophrenia.

Read More: Researchers Create the Loudest Possible Sound Underwater

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Sumbo Bello

Sumbo Bello is a creative writer who enjoys creating data-driven content for news sites. In his spare time, he plays basketball and listens to Coldplay.

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