“Of Sound Mind”: A Discussion of the Auditory Brain

“Tome [this image] captures the wonder, the awe, the beauty of sound, and the brain trying to make sense of it,” said Professor Nina Kraus, researcher at Northwestern University and author of “Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World”.

Stop. What do you hear?

We may not always think about the sounds around us, but our brain is always listening, said Nina Kraus, a professor at Northwestern University.

Kraus, auditory researcher and author of “Of Sound Mind: How Our Brain Constructs a Meaningful Sonic World”“, spoke via Zoom to a Duke audience in October. She has published over four hundred articles on the auditory system in humans and other animals and how it is affected by conditions such as autism, aging, and concussions. She discussed some of her findings and how “healthy mind” affects us in our everyday lives.

One of the slides from Kraus’ presentation. We can think of sound as having many “ingredients”.

“I think a healthy mind encompasses how we think, how we move, how we feel, and how we feel,” Kraus said. We live in a “visual world”, but for hearing people, sound plays an important role in language, music, rhythm and how we perceive the world.

One of the slides from Kraus’ presentation. The human auditory system involves not only the ears but also several regions of the brain. The “hearing brain” engages movement, cognition, and emotions while interpreting direct sensory input from all the senses.

Kraus discussed the auditory system and how much of what we think of as hearing takes place in the brain. We can think of sound as signals outside the head and electricity as signals inside the head (neural processing). When these two merge, learning occurs and we can make connections between sound and meaning.

Another slide from Kraus’ presentation. In one experiment, teaching rabbits to associate sound with meaning (in this case, more carrots) changed neuronal firing patterns in the auditory cortex, even in individual neurons. “Same sound, same neuron, and yet the neuron reacted differently…because now there’s a connection between sound and meaning,” Kraus said.

Despite how sensitive our neurons and brain are to sound, things can get lost in translation. Kraus studies how conditions such as concussions and hearing loss can negatively affect auditory processing. Even among healthy brains, we all hear and interpret sounds differently. People have unique “sound fingerprints” that are relatively stable over time in an individual brain, but differ from person to person. These patterns of sound recognition are apparent when scientists record brain responses to music or other sounds.

“One of the biological measures that we’ve used in human and animal models,” Kraus said, is FFR (frequency following response) to speech. Speech FFR can be used to analyze an individual’s auditory processing system. It also allows scientists to convert brain responses back into sound waves. “The sound wave and the brain wave look alike, which is just remarkable.”

One of Kraus’ slides. Technology called Frequency Following Response (FFR) can be used to convert brain waves back to the original sound (like a song).

This technology helps reveal how well our brain is adapted to sound. When we hear a song, our brain waves react to everything from the beat to the melody. These brain waves are so specific to that particular song or sound that when scientists convert the brain waves back into sound, the resulting music is still recognizable.

When scientists try this on people who have suffered a concussion, for example, the recreated music may sound different or garbled. Experiments that compare healthy and unhealthy brains can help reveal what concussions do to the brain and our ability to interpret sound. But not everything that affects auditory processing is bad.

Musical entrainment is said to be good for the brain, and experiments conducted by Kraus and other scientists support this conclusion. “The musician’s signature – something that develops over time -” has specific patterns and can improve certain components of auditory processing over time. Making music can also improve language skills. “Musical and linguistic signatures really overlap,” Kraus said, “which is why making music is so good for bolstering our sane minds.” Children who can sync to a beat, for example, tend to have better language skills according to some of the experiments Kraus has participated in.

Musicians are also, on average, better at processing sound in noisy environments. Musicians respond well in quiet and noisy environments. Non-musicians, on the other hand, respond well in quiet environments, but this response “really breaks down” in loud environments.

Interestingly, “Making music has a lifelong impact. Making music early in life can build a healthy mind when you’re in your seventies or eighties.

A slide from Kraus’ presentation. Musicians tend to process sounds better in noisy environments.

Exercise can also improve auditory processing. “Elite Division 1 athletes have particularly quiet brains” with less neural noise. This is a good thing; it allows incoming information to “stand out more”.

In experiments, healthy athletes also had a more consistent response over time across multiple trials, especially females.

These benefits are not limited to elite athletes, however. According to Kraus, “Being fit and flexible is one of the best things you can do for your brain,” Kraus says.

Kraus and his team have a regularly updated website about their work. For those who want to learn more about their research, they have a short video about their research approach and an online talk Kraus gave with the Kennedy Center.

Nina Kraus with a piano. “Science is a deeply human endeavor,” she said, “and I think we often forget that. It’s done by people.
Photo courtesy of Kraus and his colleague Jenna Cunningham, Ph.D.
Message from Sophie Cox, Class of 2025

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